story of electricity

7/28/2019 Story of Electricity

1/90

> A CBT PUB LIC ATI ON

' THE STORY OF

ELECTRICITY


2/90


3/90

THE STORY OF

ELECTRICITY

By

A. K. Chakraborty

and

S. C. Bhattacharya

illustrated by Mrina! Mitra

Chi ldr en' s Book Trust , N e w Delhi


4/90

'The Story of Electricity' won the first prize in

the non-fiction category in the Competition for

Writers of Children's Books held in 1983 by the

Children's Book Trust.

It is jointly authored by Dr. A.K. Chakraborty,

who is a Reader of App lied Physics in Calcutta

University, and S.C. Bhattacharya, a former Wire-

less Operator in the Indian Air Force.

Printed 1985

Reprinted 1987, 1989

by CBT 1985

ISBN 81-7011-289-3

Published by Children's Book Trust, Nehru House,

4Bahadur Shah Zafar Marg, New Delhi, and printed at

the Trust's press, the Indraprastha Press, New Delhi.


5/90

Wonders of electricity

" T

JL/ong ago there lived in Turkey a magician whowas gifted with miraculous powers. He could melt metal

without fire, produce light without oil. He had awonderful box. He could speak into it and his disciplessitting at the other end of the world could hearh i m . . . . "

That is how a fairy tale written in the 19th centurybegins. Generations of children must have been thrilledby this account of wondrous feats. But no child today

will consider this a fairy tale or that magician a man ofmiracles. All his magical powers are now within thegrasp of any man.

What performs those miracles today is known as'electricity'. It is like the genie of Aladin's magic lamp.Just as the Arabian giant, in obedience to his master's

3


6/90

command, accomplished the impossible in no time, soalso electricity has turned the incredible into commonplace.

You press a switch, and a light brightens your room.You speak into an instrument and the words reach thefar corners of the earth or even into infinite space.Electricity can transmit not only words but also pic-tures. It drives trains and trams. It makes computers'think'. It can melt metal and freeze water. It can healand it can kill. With the aid of electricity man hasachieved much more in one century than he had beenable to in all the centuries before.

True, it cannot be a fairy tale, but how man learnedto use the power of electricity is a fascinating story.And, though one can begin it with "long long ago," itis a story without an end. For even as this is beingwritten, new discoveries are being made, and it has tobe left to someone in the future to write new chapters.

4


7/90

Thales and his discovery

It all began in ancient Greece. The first hero of ourstory is Thales, a mathematician. He was a native ofMiletus, which was then a Greek colony, and he was

born about 600 years before Christ. Many tales are toldabout this extraordinary man. It is said that a friendonce told him, "It is easy for an idle thinker to grow up

to be a philosopher; but to be a successful man ofbusiness one needs much cleverness and industry."

Thales retorted, "A philosopher can achieve successeven in business if he wishes to. But a businessmancannot be a philosopher however hard he may try."

To this his friend said, "Well, then show me thatyou also can succeed in business."

Thales took up the challenge. It so happened thatfor several years bad weather had affected the olivecrop, resulting in a great scarcity of olive oil all over thecountry. Thales felt that the weather would be better inthe coming year, and production of olive ought to besatisfactory. Acting on this conjecture, he hired all theoil mills he could. When, as he expected, there was a

bumper olive crop, he bought olive cheaply, worked themills he had hired and sold the oil at a high price. Hemade a fortune and proved that he was no idle

philosopher.

Thales took a deep interest in whatever excited hiscuriosity, and he loved to experiment with every matterthat caught his attention. One day, in winter, when hewas at work, he saw on his table a piece of amber, akind of yellowish resin, covered with dust. He pickedup the amber, rubbed it on his coat to clean it and putit back on the table. A great wonder awaited him. He

5


8/90

Thales conducting his experiment.


9/90

could not believe his eyes. A few small chips of wood onhis littered table had moved and were clinging to theamber rod.

To make sure that what he saw was not an illusion,he picked up the amber again and rubbed it on his coat.Again he held it near the chips and again they moved tothe amber rod and stuck fast. Slowly he lifted theamber with the chips sticking to it. Deep in thought, helooked closely at the amber. He wondered if the ambercould also attract material other than wood. He madeexperiments and found that the amber could, but it

acquired the property of attracting other material onlyafter it was rubbed.The discovery excited Thales. He remembered the

legend of Magnus, the shepherd of Crete who, whilefollowing his flock on Mount Ida, suddenly found thathe could walk no farther. He was unable to lift his feet.What was the matter? Magnus noticed that the iron

studded soles of his boots were stuck to the rockysurface of the hill. The rock was of the kind calledloadstone.

This stone has a wonderful property. It attractsiron. All of you must have seen a magnet and havenoticed that it attracts things made of iron. The load-stone is a natural magnet and it is found in many parts

of the world. It has all the characteristic properties ofan artificial magnet.

Thales knew much about the loadstone. The Greekscalled it 'magnetite' after Magnus, the shepherd. Theword 'magnet' in English is also derived from his name.Thales knew that magnetite in its natural state attractsiron. But amber acquired the power of attraction only

when it was rubbed with something else. Could there beany relation between the natural property of magnetiteand the induced property of amber? He found noanswer to the question.

7


10/90

Perhaps, Thales assumed, the power of attractionacquired by amber was also a kind of magnetism.Although he could not explain his assumption, herecorded carefully all the results of his researches and

experiments. When Thales discovered the attractiveproperties of amber he could not imagine that his dis-covery would turn out to be one of the most valuableand significant discoveries in the history of scientificlearning, that it would lay the foundation for the studyof electricity.

Dr. Gilbert, the Royal Physician

C en tu r i e s passed by and though many philosophersafter Thales pondered over this subject of magnetism,no significant discovery relating to magnetism was

made till the time of Sir William Gilbert (1544-1603),personal physician of Queen Elizabeth I. In 1600 A.D.he published 'De Magnete' (about Magnets), in whichhe recorded the results of his experiments of 17 yearsand his theories about magnetism.

Dr. Gilbert had heard of Magnus and Thales whenhe was young and was so impressed by their discoveries

that he decided to do his own research on the subject.He found that not only amber but also such things assulphur, glass and wax became magnetic by friction andattracted other materials. He also noticed that therewere many things which, when rubbed, would notacquire any magnetic property. It was he who firstobserved the characteristic difference between the

natural magnetic property of loadstone and the inducedmagnetism of amber. Dr. Gilbert gave the magnetic

property of amber the name of 'electricity'. In Greekamber is called 'elektron'.

8


11/90

Dr. Gilbert experimented with various objects andclassified them according to their properties. He pre-pared a list of materials that would become electrifiedby friction and of those that would not. He drew up

another list of materials whose electric properties weremore powerful than those of others.10 classify objects according to theii induced power

of attraction, he devised an instrument called the'electroscope'. It was a very simple apparatus, with adry piece of straw hung in front. Dr. Gilbert would rubdifferent objects with fur or linen, hold them one after

another before this straw and carefully note down theextent each attracted the straw. He could not ascertainwhy and how an object acquired the power of attractionby friction. But the results of his researches paved theway to many scientific discoveries.

When Dr. Gilbert wrote his book, he did notimagine that he would raise a controversy that would

last over generations to come. Nor that he would oneday be hailed as the father of the science of electricity.

Gradually Dr. Gilbert's book came to be known tomost European scientists. To many of them the theories

propounded by the ancient Greek philosophers andscientists were the last word and they were unwilling toaccept new ideas. Yet some were fascinated by the

author's scientific vision. A few even began theirresearches along Dr. Gilbert's line, but no significantadvancement was made in this field during the next60 years.

Otto von Guericke, the Burgomaster

T h e man who, after Dr. Gilbert, made notablediscoveries about electricity was Otto von Guericke

9


12/90

(1602-86). He was the Mayor of Magdeburg, a city inGermany. He was a very able administrator, but inspite of his mayoral responsibilities, he found time forscientific research.

The people of Magdeburg looked upon their Mayorwith suspicion. They believed that von Guericke wasdevoted to witchcraft and was in league with the devil.On seeing him in the street, many city dwellers wouldhasten to keep themselves at a safe distance from theirburgomaster. Some of them considered him insane.


13/90

The day von Guericke announced that he haddevised an instrument to create a vacuum, they had nodoubt that their Mayor's mental derangement wascomplete. Could any sound mind conceive such an

absurd idea? Was it possible to suck away air from avessel? Aristotle, the great savant, had said, "Natureabhors a vacuum." Was Guericke, then, refuting Aris-totle? Who but a mad man could have such audacity?

Guericke was indifferent to what the people saidabout him, but he became the topic of discussion here,there and everywhere in the country. Rumours spread

and at last reached the ears of His Imperial HighnessFerdinand III. The post of mayor was important andthe person in the mayoral chair should command therespect of all citizens. The Emperor decided to visitMagdeburg to check whether Guericke was as mad asrumour made him out to be. In a letter to the Mayorannouncing his visit, he wrote, "I hear you have invent-

ed the art of creating a vacuum. And I hope you willprove the justness of your claim."

On receiving such a message from the Emperor, vonGuericke was naturally worried. But within two weekshe made all the necessary arrangements to receive theEmperor. And the day Ferdinand arrived, the city ofMagdeburg was steeped in colour, with the streets gaily

decorated and houses and walls freshly painted. Thecity dwellers, clad in their best clothes, lined the streetsto receive their royal guest.

A reception was held at the City Hall. All the eliteof the city were invited and there was food and drinkin abundance. The feast over, von Guericke stood upand, without any introduction, said, "Presently I shall

demonstrate to you the operation of my new air pump.I shall suck out all the air from a hollow sphericalvessel and create a vacuum."

The City Hall resounded with laughter. The

11


14/90

Emperor looked at Guericke in some doubt. One of hiscompanions asked, "Won't there be any device to peepinto the sphere to see the vacuum?" Once more therewas loud laughter. Even the Emperor could not helplaughing.

Von Guericke remained calm. He said, "Not farfrom here is a large open ground. There I will hold mydemonstration. Let us all go there."

The Emperor rode to the appointed place withthe Mayor. The others followed them in procession.On reaching the lawn the city dwellers assembled bythe Emperor's side.

The Mayor then began his demonstration. He heldup two copper hemispheres, each fitted with a metalring, and showed that, by setting the two halves face toface, they would form a sphere. He repeatedly put thetwo hemispheres together to form a sphere and pulledthem apart to show how easily it could be done. Then

he brought his air pump, a metallic cylinder with aspout on one side and a big handle on the other.

He again piessed the two halves of the coppersphere together, connected the spout of the air pump toa valve attached to one half, and declared, "Now I shallsuck out all the air from this round vessel."

The spectators watched silently as von Guericke

began moving the pump handle up and down. Within ashort time the movement of the handle slowed down.One could see that the Mayor had to use considerableforce to operate it. When the handle refused to move,von Guericke stopped. He was bathed in sweat.

Wiping his forehead, he looked at the Emperor andsaid, "Your Majesty, I have sucked out all the air. A

vacuum has been created within this sphere."Then, turning to the spectators, he said with a

pleasant smile, "One of our guests here wanted to knowif he could peep into it. He would see very little there,

12


15/90

for we cannot see everything with our naked eyes. Mancan see more with the light of intellect and reason thanwith his physical organ of sight."

He went on to explain. "When the sphere was filled

with air, the internal pressure within the vessel and theexternal pressure of the atmosphere remained equal andthey annulled each other. That is why it was easyenough to pull the two halves of the sphere apart. Now,there being no air within the vessel, the tremendouspressure exerted by the atmosphere will hold the twohalves together so tightly that it will not be quite easy

to separate them."Then he picked up the vessel by a ring and began to

shake it. All the spectators expected to see the twohalves go apart. They stuck firmly to each other. Thenvon Guericke turned to the Emperor and said, "YourMajesty, I would like to see if you can pull the twohemispheres apart."

Ferdinand rose from his seat and von Guerickehanded the vessel to him. The Emperor held it firmly inhis hands and tugged mightily at the two rings but to noeffect. Ferdinand was a strong man. And when hecould not pull the vessel apart, the spectators wereastonished.

More wonders awaited them. Von Guericke made asign. At once, four powerful horses were broughtbefore him. Two horses were harnessed to each of thetwo rings of the spherical vessel and, under the lash ofwhips, they tugged at the vessel from either side. But itdid not split apart. Von Guericke made another signand four more horses were brought. This time eight

horses, four on either side, were engaged in this tug-of-war, but the two halves of the sphere held together. Atlast 16 horses, eight on each side, were harnessed to therings. This time the vessel split with a bang.

Emperor Ferdinand was highly impressed. He was

13


16/90


17/90


18/90

convinced of von Guericke's genius. The Emperorcongratulated the Mayor and told him that he shouldcarry on with his researches. He also said, "If you evermake another such discovery, do not forget to let meknow. I expect to see you achieve many more successesin the domain of science."

This was a memorable moment in von Guericke'slife. And it has a particular significance in this story ofelectricity. Henceforth von Guericke could do hisresearches and experiments freely and he turned toelectricity.

He read Dr. Gilbert's book through and through.Having examined carefully the doctor's theories, hebegan his own experiments. He observed that to ener-gise amber or glass by rubbing them with fur or linenwas a clumsy and tiresome process and it yielded verylittle electricity. After various experiments he devised

an apparatus that could generate a considerable amountof electrical energy.

Von Guericke made a ball of sulphur, perforated itin the middle, and then passed a metal rod through thehole. Then he fixed a handle to the rod, so that, byturning the handle, one could turn the sulphur ballround and round. Von Guericke demonstrated that if

one held the sulphur ball with gloved hands and turnedthe handle, the revolving ball would generate plenty ofelectricity. The electrical energy thus produced remain-ed concentrated within its source which, in this case,was the sulphur ball. Von Guericke named it 'staticelectricity'; and he called the instrument he ' invented'electrostatic generator '. He also showed that the

sulphur ball, in its energised state, could attract paper,chips of wood, thin metal sheets, feathers.

He also discovered that electrical energy could betransferred from one object to another. It was he whofirst noticed that a sheet of metal brought in contact

16


19/90

with an electrified sulphur ball acquired the property ofattracting other objects. After having experimented withmany different objects, von Guericke came to the con-clusion that a thing could be electrified by being brought

in contact with another electrified object. In otherwords, electrical energy could be transferred by contact.

Stephen Grey (1670-1736) and his experiments

T h e 'electrostatic machine' invented by Otto vonGuericke facilitated the researches and experiments oflater scientists. Half a century after his death anothersignificant invention was made in the sphere of electri-cal science. The name of the inventor was StephenGrey.

Grey belonged to a lower middle class family of

England. He was greatly interested in science, but thelittle amount of money he received as his pension wasnot enough even for a bare living. So, it was hard forhim to buy the books and instruments he needed forhis experiments.

Luckily, he had a friend, Granvil Wehler, who wasrich and was also interested in science. Wehler had no

doubt about his friend's genius and was certain thatGrey would one day achieve undying fame. So he wasready to give money to Grey for his experiments.

One day when Wehler was returning from an opera,by chance he met Grey in the street. Seeing his friendgrave and sad, he asked, "What is the matter, Stephen?Why do you look so glum? Is it toothache?"

"Granvil," Grey said, "to get rid of toothache, onecould get rid of one's teeth. But when a man's painrises from the deepest recesses of his heart and burnshis soul, what can he do?"

17


20/90

Wehler could not understand what his friend wasdriving at. But it occurred to him that what Greywanted was a sympathetic listener to whom he couldopen his heart. Wehler put his hand on his friend's

shoulder and said, "Come to my house and I shall hearall about your problem."

Wehler lived in a beautiful mansion at OtterdenPlace in London and he took his friend there. As theysat face to face, Wehler said, "Stephen, why are you so

broken-hearted? I have never seen you so downcastbefore. What is the matter?"

Grey answered, "You know, my dear Granvil, Iwas never eager to grow rich, never aspired to fame orsocial status. I just wanted to comprehend the natureof this world and, through experiments, to discoversome facts that would, perhaps, change the whole his-tory of mankind. But a poor man like me can neverhave his hopes fulfilled."

"Stephen, tell me all about your plans. I may beable to help you."

"I wish to carry out some researches on electricity.It is a wonderful power. Till now it has not beenpossible to know its real nature. Yet, Granvil, I oftenthink this electricity will perform miracles some day. Itoften occurs to me that once we can know the true

nature of electricity, the true nature of the universe willreveal itself to us."

"I too am curious to know more about electricity,"Wehler said. "I have plenty of money, but no brains. IfI had your gift of intellect, I would, perhaps, set up myown laboratory and begin my own researches. I likeyour plans. I like them because, in your hopes anddreams, I hear the echoes of my own. So I give you anoffer. If you do not mind I shall make a suitablelaboratory for you in my own house. But, of course, onthe condition that you take me as your research

18


21/90

assistant. Do you agree?"

Overwhelmed with joy, Grey took his friend's handsin hi5 and said, "Do you really mean it, Granvil?"

Granvil smiled and said, "Yes, Stephen. But do not

think I am spending money without any personalinterest in the matter. I have faith in your ingenuity. Iknow you have a great future ahead of you. Given theright opportunity, you will certainly make some valu-able contributions to science. When you grow famousas a scientist, I, as your assistant, shall go down intohistory along with you."

A few months later the two friends were busy intheir laboratory. But what a laboratory! It had all theappearance of a veritable cobweb. There was an over-hanging network of threads tied up all around the wallswith metal hooks.

The two friends sat in two corners of the room.Grey had a glass rod in his hand. One end of a longthread was fastened to the glass rod and other wasattached to an ivory ball. Wehler was sitting beside hisfriend with a board on which some feathers wereplaced. Grey rubbed his glass rod with a piece of linenand said, "Granvil, hold the feathers close to theball."

Wehler did as he was told. But the feathers showedno sign of movement. Wehler was silent.

Grey grew impatient and asked, "Any result?""No," replied Wehler.Grey rubbed the glass rod harder and harder, but to

no effect. At last he said in despair, "Granvil, there canbe no reason why it should not work. What then "

Wehler laughed and replied, "My friend, how canyou expect success to come to you so easily? Havepatience, think coolly and you will certainly be able tospot the trouble. No more today, I pray you. Let us goand sit beside the Thames."

19


22/90

The year was 1729 A.D. It was a cold wintry night.The time was about 8 p.m. Thick fog enveloped thearea. Grey tucked the collar of his overcoat round hisears and set out for Otterden Place. He had a parcelunder his arm.

Unconscious of the bustle of the streets, he walkedthinking of the experiments he planned for the night.For some months he had been trying to conduct elec-tricity through long threads, but all his efforts hadfailed. Now he had realized the cause of his failure.Tonight he would not fail.

Shouts and curses, the tramp of horses and rattle ofspeeding wheels nearby rudely made him aware of theworld around him. Sensing danger he jumped to a sideof the road. Mercifully for him and science, he escapedbeing run over by a coach.

Grey realized that, if he thus remained buried in

thoughts while walking, he would sooner reach hisgrave than his destination. He became more careful and,holding his precious packet tightly, quickened his paceand soon reached Wehler's mansion.

Wehler himself opened the door and said, "Come,sit beside the fire and warm yourself." But Grey was soexcited with the thought of his experiments that he

heard not a word of what his friend said. He had notime to idle away. He must put his theory to the test.

"Granvil," he said, "I have found the solution tomy problem. There was a serious flaw in our experi-mental process. This time I am confident of success.Come and help me."

The two friends hurried into their laboratory. Grey

untied his packet and took out a large reel of threadand an ivory ball. Then he drew out a long cord fromthe reel and, with the help of his friend, fastened it tothe wall from side to side. He tied one end of the cordto the glass rod and the other to the ivory ball. He

20


23/90

examined thoroughly the points on the walls to whichthe thread was fastened and said, "It is all right. Now,hold the featheis near the ivory ball."

Wehler did that and Grey began to rub the glass rod

with a piece of linen. Within a few moments Wehlercried out, "Stephen, you have done it! The feathershave leaped up and are stuck to the ivory ball!"

With these words, Wehler announced to the world agreat and significant achievement. Now, for the firsttime, man could transfer electrical energy from oneplace to another.

Overwhelmed with joy, Wehler embraced his friendand said, "Your success is astounding! Now tell mehow you did it. What was the flaw in our previousexperiments?"

The two friends sat before the fireplace. Grey said,"Only this evening I could realize, by chance, the mis-take we made in our experiments. The metal hooks that

we used for fastening the cords to the walls are them-selves good conductors of electricity. So the electricitygenerated in the glass rod was being bypassed to earththrough them before it could reach the ivory ball.Having realized this, I fastened the thread to the hookswith silk cords so as to avoid any direct contact bet-ween the hooks and the thread. Silk being a non-

conducting material, it stopped the electric current frombypassing through the metal hooks. So, this time, theelectricity produced in the glass rod could easily reachthe ivory ball through the long thread."

With Wehler's assistance and encouragement Greycontinued his researches and found out that somematerials were good conductors of electricity, whilemany others were poor conductors.

The materials that prevent the flow of electriccurrent are known as insulators. These insulatingmaterials are now used for isolating or converting live

21


24/90

conductors. On the basis of the discovery made byGrey, electrical wires, coated with rubber or plasticmaterials, are being manufactured on a large scale.

Charles Dufay (1698-1739)

T h e next significant discovery was made byCharles Dufay, a Frenchman. He observed that there

were two kinds of electricity. And he found that theelectricity produced in a glass rod when rubbed withsilk and that generated in a resin rod when rubbed withfur are not homogeneal, not of the same kind.

Charles Dufay had observed that, if two glass rodswere rubbed with silk and then hung side by side onsilk cords, the rods repelled each other. And it was

'likes' that repelled. If a glass rod rubbed with silkand a resin rod rubbed with fur, were hung side by side,the two attracted each other. So Charles Dufay came tothe conclusion that the electricity of the glass rod andthat of the resin were different.

Let us electrify different objects by rubbing themwith different materials. Now, if we bring these electri-

cally charged objects close to the glass or the resin rods,each of these objects will either attract or repel one ofthe two rods, the glass or the resin.

So we see that the electricity of any electrical objectcorresponds or, to use a more technical term, is homo-logous either to the electricity of the glass rod or to theelectricity of the resin. We do not come across an

electrified object whose electric property is heterologous,that is corresponds to the electric properties of both theglass and the resin rods.

We may, therefore, conclude that there are only twokinds of electricity. The electricity produced in a glass

22


25/90

rod rubbed with silk was called 'vitreous electricity' orglass electricity. And the electricity of a resin rodrubbed with fur was known as 'resinous electricity'.Later, Benjamin Franklin named the first 'positive

electricity' and the other 'negative electricity'.

An accidental discovery

It was by accident that another important discovery

was made. PietervanMusschenbrock(1692-1761),apro-fessor of Leyden University, was experimenting on thepossibility of storing electricity in water in a glass flask.He had an iron rod with two silk cords. One end of ametallic wire, attached to the iron rod, was passedthrough the stopper of the flask.

The professor thought that, if the iron rod were tobe electrically charged, the current flowing through thewire would electrify the water. And glass, being a non-conductor, the electricity in the water would find noway out. As the professor held the flask in one hand andtried to pull the wire out of the iron rod, he received aterrible electric shock. In trying to ascertain the causeof this phenomenon, he invented, accidentally, an elec-tric condenser for storing electricity.

The apparatus is known as Leyden Jar. It consistsof a cylindrical glass vessel lined inside and outsidewith metal foil. A brass rod is passed through the corkat the mouth of the jar. To the lower end of this rodis attached a brass chain which keeps electrical contact

between the rod and the metal coatings inside the jar.The Leyden Jar became popular in no time.Professional magicians fired their cannons by ignitinggunpowder by the electricity stored in the Leyden Jar,causing fear and wonder among their audience. Some

23


26/90

used it to give themselves or others electric shocks.It is said that a French priest, Christophe Claire,

found it useful to demonstrate to some sceptical factoryworkers his power to inspire divine feeling in others.

On a Sunday evening, just after prayer, sixteen of themassembled, as they were asked to, in the courtyard infront of the church.

Claire appeared carrying a box wrapped in red clothand two crosses dangling from it. The priest asked themen to stand, hand in hand, in a circle. He thenapproached them and asked two of the men to hold the

two crosses. The moment the two men touched themall sixteen sprang up and were scattered about thecourtyard.

Whether the feeling this inspired was divine is notknown, but there was nothing divine in the power thatmade the sixteen bedridden for days. Claire had con-cealed within his box a small portable generator and a

Leyden Jar and just before approaching the workershad turned the handle of the generator. The two crosseswere connected to the two electrodes of the jar and,when the two men touched the crosses, a powerfulelectric current began to flow through the human chain,making them bounce.

Benjamin Franklin (1706-90) and electricity

Benjamin Franklin has made important contri-butions to the science of electricity. He was a versatileman, literary artist, politician, social worker andscientist, all in one. In 1746 one Dr. Spence had shownhim a few experiments in static electricity and Franklingrew interested in the subject. He repeated these experi-ments and, observing the similarity between the sparks

24


27/90

of electricity he produced and lightning, he wrote athesis entitled, 'The similarity between lightning andelectricity'. In this he expressed the view that by meansof a suitable conductor the electricity of lightning

could perhaps be brought down to earth. When hispapers were read at the Royal Society meeting, themembers present laughed.

To give a fitting reply to this ridicule, Franklinresolved to prove the truth of his theory by an experi-ment. He made a big kite and on a cloudy day, he flewit high in the sky. He tied a key to the cord of the kite

and held the key with silk lace over it to prevent elec-tricity flowing through the cord from passing throughhis body. Now, as he brought one end of anotherconducting wire quite close to the key, a bright sparkoccurred. Thereafter, by connecting the key to a LeydenJar, he was able to store in it a good amount of elec-tricity. The experiment was dangerous and Franklin

was lucky to escape electrocution.On the basis of this discovery, lightning arresters or

conductors were devised to protect building fromthunderbolts. The lightning conductor is a metallic rod,with a number of sharp points, put on the roof ofbuildings. The lower end of the rod is connected byiron or copper wire to the earth. If there is a flash of

lightning, it can cause little or no damage to thebuilding because the electrical discharge is drainedaway to" the earth through the lightning conductor.

Another significant contribution Franklin made ishis theory about the nature of electricity in materialobjects. Before Franklin, an apothecary named WilliamWatson had expressed the view that every object con-

tained two kinds of electricity. Franklin studied theimplication of this and explained the reason why anobject became electrified by friction. He said that everysubstance in its natural state contained equal quantities

25


28/90

Franklin's famous kite experiment


29/90


30/90

of vitreous (of glass) electricity and resinous (of resin)electricity. Matter being composed of two converseelectrical charges of equal amount, an object, in itsnormal state, did not manifest any electric property. It

was only at the time of friction that the objects respond-ed electrically to each other and became electricallycharged. Because glass electricity and resin electricityneutralised each other's action, Franklin called theformer positive and the latter negative electricity.

It should be mentioned that these two kinds ofelectricity are equally elemental. It is not that positiveelectricity is richer in any special property than negativeelectricity. Nor is it that negative electricity is deficientin any particular property. It is only for conveniencethat an international convention has been establishedto call glass electricity 'positive' and resin electricity'negative'.

How a skinned frog excited Galvani

F r o m Stephen Grey's researches man conceivedthe idea of using electricity, but current produced by

the electrostatic generator was transient, that is, notpermanent. It was not possible to provide the necessaryelectromotive force to perpetuate the flow of current ina circuit. The scientist who first made a significant dis-covery along this line was Luigi Galvani.

Dr. Luigi Galvani (1737-98) was a professor ofanatomy in Bologna, Italy. He was a specialist in

physiology and therapeutics. No one knows for certainhow he suddenly grew interested in electricity. But it issaid that one day, he hung the flayed carcass of a frogon an iron railing by a copper hook to dry. As it swungin the breeze, Galvani observed that the legs of the frog

28


31/90

shrank as they came in touch with the railing.He watched this phenomenon keenly for sometime

and came to the conclusion that electricity was thecause of the muscular contraction of the frog's legs. He

had heard of the fish called torpedo which kills ordisables its prey by electric shock. He also knew of theray fish that uses its electric organ for defence and tocatch its prey. Fishermen often talked about havingreceived severe shocks while catching these fishes. This

29


32/90

led him to the conclusion that there was electricity inthe body of an animal. He called it animal electricity.He also expressed the opinion that it was this electricityin the body of the frog that made it shrink at the touch

of the iron rail.Though Galvani's theory of 'animal electiicity' was

discarded, the importance of his contribution to thescience of electricity cannot be denied. His discovery

paved the way to many new scientific researches whichled ultimately to the invention of the 'electric cell'.

Going into the history of science we see that manywrong theories have helped the ad vancement of scienti-fic learning. Just as scientists establish a truth by prov-ing a theory, so also they discover new truths whiledisproving one.

Volta's electric cell

C o u n t Alessandro Yolta (1745-1827) was a pro-fessor of physics at the University of Pa via, Italy. Afterrepeating Galvani's experiment in his laboratory hebegan his own research. He demonstrated that, if

Galvani's views on 'animal electricity' were accepted,many other experimental truths of science could not beexplained.

Volta knew that in Galvani's experiment the skinnedfrog was slung on the railing with a copper hook. Heobserved that, if the copper hook was replaced by aniron hook, the legs of the frog would not shrink at the

touch of the iron rail. So it was established that to effectthe contraction of the frog's legs two different metalswere necessary. If the electricity within the body of thefrog itself was really the cause of contraction, whyshould two different metals be necessary to effect this?

30


33/90

Volta drew the conclusion that in Galvani's experi-ment the source of electricity was chemical reaction.He said that two different materials coming in contact

with a proper solution caused this reaction. In Gal-vani's experiment it was an aqueous (of water) solutionpresent within the body of the frog that helped thechemical reaction producing electricity.

Volta did not stop here. To prove his theory heproduced electricity by using a suitable solution insteadof a frog's carcass. By this experiment was invented the

first man-made 'electric cell', or 'battery' . Volta foundthat electric cells could be produced by placing paperor cloth, moistened with sulphuric acid, within zinc andcopper sheets.

In order to strengthen the electric current thus pro-

31


34/90

duced, Volta made a stack or pile of copper and zincdiscs arranged alternately. Within each pair of discs heplaced a sheet of blotting paper soaked in sulphuric

acid. Electric current began to flow in the circuit whenthe two ends of the conducting wire were connected totwo cell plates (electrodes).

The pile of metal plates devised by Volta is knownas the 'Voltaic pile.' The electric cell he made bydipping a zinc rod and a copper rod into a vessel con-taining dilute sulphuric acid is called the 'Voltaic cell'.

Volta's discovery ushered in a new era in the historyof the science of electricity. Many scientists tried toimprove the quality of electric cells and succeeded ininventing various kinds of batteries. But none of thesecould yield any considerable amount of electricity.

Nowadays geneiators are used to produce electri-city. Portable batteries, however, serve many useful

purposes. They are used in torches, portable radio setsand motor cars. Even today batteries are indispensableto our telegraph and telephone systems. The apparatusby which radio signals are transmitted from artificialsatellites is powered by electric cells. Ever since Voltapublished his theory of electricity, the electric cell hasbecome an indispensable article in science laboratories.

Volta was more fortunate than most of his pre-decessors. He achieved honour and fame during hislifetime. A unit of electricity (potential difference) wasnamed after him.

The Royal Institution : Sir Humphry Davy

It was soon found that with a combination of manycells very powerful batteries could be made. And fromthose batteries very high and stable electric current

32


35/90

Davy's apparatus for gas analysis.

could be obtained. In 1800 the Royal Institution ofLondon built such a high power battery. This waslargely due to the efforts of Count Benjamin Rumford,the founder of the Institution, who was ever trying toimprove its research facilities.

Rumford was finding it hard to get the money need-ed to buy equipment. Then he hit upon a novel plan.

He knew that the common people were eager to knowabout the discoveries and inventions relating to elec-tricity. Couldn't he exploit this popular curiosity toraise funds? Would not people be willing to spend alittle money to listen to lectures on electricity and to

33


36/90

watch demonstrations of scientific 'magic'?He drew up a programme for a lecture series and

announced it in the newspapers. This met with anenthusiastic response. As days passed, more and more

people began attending the lectures. But Rumfordfound that, though the scientists of the Royal Institu-tion were learned, giving lectures to the lay publicneeded more than learning. He started looking for asuitable man, and, on the advice of a friend, appointedHumphry Davy (1778-1829).

As Rumford took his seat among the audience to

hear Davy's first lecture one evening in 1801, he realiz-ed that he had made a wise choice. Though only 23years old, Davy was learned in the science of chemistry.Above all, he knew how to capture the attention of hisaudience, how to excite curiosity about things un-known, how to make his lectures enjoyable. Hissplendid oratory, accompanied by practical demons-

trations, enthralled his audience.Davy's skill and novelty of expression made his

lectures popular within a short time. Many who heardhim once came again and again to hear him. Moneyflowed into the Royal Institution. Humphry Davybecame a familiar name amongst the elite of London.

But Davy would not rest satisfied with his popu-larity. He was a talented scientist and, being associatedwith the Royal Institution, he found the opportunity towork in its well-equipped laboratory. What attractedhim most was the Voltaic battery and he tried severalexperiments with it.

One day, without any set purpose, he took the

two wires that were connected to the poles of thebattery and dipped them into a beaker of water. Henoticed, at once, bubbles rising at the ends of theconducting wires. What caused these bubbles? Heremembered having read an essay written by William

34


37/90

Nicholson and Sir Anthony Carlisle. They too had sentelectric current through water and observed bubblesrising at the two poles of the conductors. They assumedthat, during the passage of the electric current, water

discharged oxygen and hydrogen gases and this causedthe bubbles. But they could not come to any definiteconclusion.

Davy began experiments to ascertain the nature ofthe gases and the cause of the bubbles. He took dis-tilled water in a beaker and put into it two conductingwires. Beneath the two dipped ends of the wires he

placed two test-tubes so that the gas produced in thewater in the beaker might accumulate in the test tubes.Then he connected the wires to the poles of a batteryand let the electric current flow through the water. Atonce, the gas produced in the water came out in theform of bubbles and began to gather in the test-tubes.Davy noticed that the gases were not accumulating in

the same proportion in the two tubes. The volume ofgas in one was twice as much as that in the other. Afterletting the current flow through the water for some-time, he managed to gather some amount of the gases.

Davy tested and analysed the gases, and found thatthey were hydrogen and oxygen. He also observed thatthe volume of hydrogen was twice as much as that of

oxygen, the exact composition of water. Davy realisedthat electric current had caused this chemical dissocia-tion of water into its two basic elements.

If water could be divided into its basic ingredients,why not other matter as well? This was an epochmaking idea. As a chemical scientist, Davy knew thatthere were materials whose ingredients could not beseparated by any process yet known. It occurred to himthat, perhaps, electricity could accomplish this. Davybegan new experiments and succeeded at last in sepa-rating such materials as could never before be found in

35


38/90

their pure state. Davy's success began a new era ofchemical science. And a new method of employing themysterious power of electricity came into our hands.

The process invented by Davy is known as electro-

lysis and it is now being extensively used in the indus-trial field. The process had enabled man to use metalsfor various purposes and to extract metals at lessexpense.

Metals have been used by man from the very earlydays of human civilization. It was perhaps copper thatman first began to use, because copper was the only

metal that was available in its original state and couldbe used without being refined. The ancient people knewthat copper could be forged into desired shapes andmade into weapons. They had also been using iron withother metals. Yet centuries passed before man couldlearn the process of extracting metals from minerals.And even when it was learnt, the process of separating

metals from mineral ores was found to be laborious andexpensive. It was the science of electricity that changedall that.

Extraction of metal : Charles Martin Hall

T o d a y we use aluminium for various purposes. It isa light and shining metal and that is why it is moreuseful than any other.

There is a great store of aluminium on the surfaceof the earth. Scientists realized that the physical pro-

perty of aluminium had immense practical value. Buttill about the end of the 19th century, production ofaluminium was very expensive. In 1852, the cost ofproduction of a pound of aluminium was nearly 550U.S. dollars. That made it costlier than gold and silver.

36


39/90

A few years later Henri de Ville, a French chemist,invented a better and less expensive method of extract-ing aluminium. In an exhibition in Paris, he displayedbefore his spectators a number of aluminium rods. Thealuminium was produced at a cost of 50 dollars apound.

Napoleon III, the Emperor of France, visited thatexhibition and was fascinated by the aluminium rods.De Ville presented to the Emperor an aluminium toyfor his little son. The Emperor placed an order forplates, knives, spoons, made of aluminium, to be usedat royal banquets. Distinguished guests had aluminiumplates and cutlery, while others had to be content withplates and spoons made of gold or silver!

The Emperor wanted to have weapons made ofaluminium. But at that time aluminium was not readilyavailable and there was no means of increasing its

production. Man had not yet mastered the art ofextracting pure aluminium from minerals. That waswhy aluminium could not be extensively used like othermetals. Scientists, however, knew the potential of thismetal and many were doing research to find a way toextract aluminium at low cost. The first scientist tosucceed in such experiments was Charles Hall (1863-

1914).In 1880, Hall was a student of Oberlin College in thecity of Ohio. He took special interest in chemistry andspent much of his time in the chemical laboratory. Oneday, one of his professors casually remarked, "Theman who can invent a method of producing aluminiumat low cost will have done a great service to mankind

and become a man of wealth." Charles Hall decidedthat he would be that man.

After graduation from Oberlin College, Hall wenthome and talked to his father about his plans forresearch. His father, sure of his son's genius, asked him

37


40/90

to go ahead. Charles Hall built his working shed in thebackyard of their house, installed the equipment heneeded and started his experiments. Working day and

night he was able to find within nine months a simpleand inexpensive method of producing aluminium withthe aid of electricity.

Hall's process was to melt aluminium oxide andsend an electric current through the molten metal,causing a chemical dissociation. The oxygen liberatedfrom the mineral gathered round one of the electrodes,

while pure aluminium accumulated at the bottom of theother electrode.

With the advent of this electrolytic process ofextracting aluminium, the price of aluminium began tofall. As a result of Hall's achievement, aluminium nolonger remained the metal of the rich. Things made ofaluminium began to be used in every household.

Today, not only aluminium but also other metals,such as copper, lead, zinc, are being extracted andrefined by electrolysis. Another important applicationof the electrolytic process is what we call electroplating,that is, coating of iron, copper, tin and other metalswith nickel, chromium, zinc, gold or silver. Such acoating on iron prevents its rusting.

It was known from Volta's discovery that electricitycould be produced by chemical reaction. And Davy'sresearches had shown that just as chemical reactioncauses electric current, so also electric current cancause chemical reaction. Now, Charles Hall had gone astep further.

After them other scientists made significant dis-coveries in close succession. As a result the actualrelation between electricity and magnetism becameclear.

38


41/90

Magnetism and electricity : Hans Oersted

F r o m olden times man had been thinking of the

wonderful magnetic property of the loadstone. But thecause of magnetism was not known. Many scientistsassumed that magnetism and electricity were inter-related. One day, in 1820, in a classroom at the Uni-versity of Copenhegen, it was proved accidentally thatthey were not wrong in their assumption.

Professor Hans Christian Oersted (1777-1851) wasexplaining to his students the functions of the variouscomponents of a battery that was on the table beforethem. He connected a wire to the two poles of thebattery to demonstrate how electric current wasflowing through the conducting wire.

On the table was a small compass. It was not in any

way related to their topic of discussion that day. Thecompass happened to be just beneath the wire connect-ed to the battery. Suddenly Oersted noticed that theneedle of the compass, instead of pointing to the north,was pointing to the east. He could not believe his eyes!

He disconnected the wire from the battery. Instantlythe compass needle swung several times, then stopped,

pointing steadily to the north. Oersted was astonished.Had he really seen the needle pointing to the east?Could electric current have had an effect on thecompass?

The young students in the room looked at him insurprise as he stopped what he was saying about theVoltaic cell in mid-sentence. He appeared distraught.

They started whispering and Oersted suddenly realizedwhere he was. It was impossible for him, that day, totake his class. He told his pupils, "Let us stop heretoday. We shall discuss the rest tomorrow."

The moment the students left the classroom, he

39


42/90

took up the compass. Was the compass all right? Itwas. The needle was pointing steadily to the north. Heconnected the wire again to the two poles of the batteryand held the compass close to the wire. No, his eyeshad not belied him. Just as electric current began toflow through the wire, the needle flung itself away fromthe true north. He also observed that if the direction ofthe electric current was changed, the needle of thecompass changed its direction.

Highly excited, the Professor ran from one class-room to another calling to his colleagues to come tohis laboratory. Seeing him thus excited, his fellow pro-fessors knew that he must have made a very importantdiscovery. They came and assembled in his laboratory.Prof. Oersted repeated the experiment before hiscolleagues. All of them, were amazed. It was proof thatthere was magnetism in electric current.

Oersted published the results of his experiment. Thenews of his discovery soon spread far and wide andreached Andre Ampere, professor of a polytechniccollege in Paris.

Ampere and his electromagnet

A n d r e Marie Ampere (1775-1836) was a very sadand lonely man. Never could he forget a dreadful nightof his boyhood. He was only 14 then. The family had

just finished supper and Andre was absorbed in hisstudies. All of a sudden he heard an outcry. A group of

rebel soldiers broke into their house and draggedAndre's father away. All his entreaties and all hismother's tears were in vain. Andre's father never came

back. He was one of the numberless men and womenwho weie the victims of the guillotine during the

40


43/90

French Revolution (1789-92).The tragic death of his father changed Andre over-

night. From his childhood, his father had been his onlycompanion and playmate. Andre's father could discernin his son the possibility of a great future. So he tried togive his son what opportunities he could for the fullflowering of his genius. He even helped Andre in hisstudies. Along with other subjects he taught himGreek and Latin.

But Andre took no special interest in these classicallanguages. He was in love with mathematics. ThoughAndre's father could not help him much in his favouritesubject, he bought his son many valuable books onmathematics. Andre began to learn on his own. As allthe good and dependable books on mathematics werewritten in Latin, he learnt that language.

After his father's death, it was he who became the

main support of their family. He began to earn moneyby teaching children mathematics in their houses. Afterhis day's toil he would pursue his own studies. He grewlearned in mathematics, physics and chemistry.

He married at the age of 20. Some time later, hejoined a school in Lyons as a teacher of physics andchemistry. But even then he was absorbed in the study

of mathematics. Within a few years he published hisfirst book, 'Considerations on the Mathematics ofGambling. ' In the book he presented his theory that ahabitual gambler would surely be a loser in the longrun. The subject he treated in his book was not one toattract academicians, but the manner in which he

presented his mathematical arguments highly impressed

many of the distinguished mathematicians of his time.In 1804 came another shock to Andre Ampere. His

wife died. He was only 29 then. A year after thatAmpere left his job at the polytechnic school and wentto Paris, where he joined a college as a professor.

41


44/90

When he read Oersted's thesis, it excited his interestin magnetism and he began his researches. Within a

short time Ampere discovered that when electriccurrent flowed through a conductor, its magnetic effectcould be felt all round the wire itself. In other words, amagnetic field was created around the path of the

42


45/90

electric current.He also observed that when electric current was sent

through two parallel wires in the same direction, the

two wires attracted each other. And, if the direction ofone current was changed, the two conducting wiresrepelled each other. Then, in order to determine therelation between the forces of attraction and repulsionwith reference to the value or strength of the current, heworked out a mathematical equation which is even nowused by scientists.

Ampere also showed that the magnetic field aroundthe conductor was circular. This phenomenon led himto the assumption that, if the conducting wire could betwisted and turned into a loop, the intensity of themagnetic field through the loop would increase. Ampereexperimented with his idea and proved it beyond alldoubt. Then he wound the conducting wire spirally

into a coil and succeeded in creating a very powerfulmagnetic field at the centre of that coil.

Thereafter Ampere invented the process of makingan artificial magnet. He noticed that an iron rod placedwithin the centre of a coil of insulated conducting wireturned into a powerful magnet. This artificial magnetwas much more powerful than a natural magnet.

A magnet thus artificially made is called electro-magnet. Through his experiments Ampere was able toshow that for making artificial magnets bars of softiron were more suitable. Such an iron rod, placedwithin a coil of wire through which electric current wasflowing, instantly became a magnet. But. the momentthe circuit was broken and the current stopped flowing,

the iron rod lost its magnetism. In other words, softiron became a temporary magnet under the influence ofelectric current.

Ampere saw that for magnetising a steel rod highelectric current was necessary. Once magnetized, a steel

43


46/90

rod retained its magnetism even after the electriccurrent flowing through the coil was stopped. Thuselectric current turned a steel rod into a permanentmagnet.

The application of electrical science on a wide scalebegan with the discovery of the electromagnet. Theartificial magnet is now being used not only in variouselectrical instruments but also for generating electricity.

The electromagnet serves many of our householdneeds. A visitor to our house presses a button at thedoor and an electrical bell within announces his arrival.The telephone rings and draws our attention to onewho is far away. The action of electric bells and tele-

phones depends on the property of the electromagnetBut the most wonderful use of the electromagnet is intransmission of messages to distant lands. This systemof transmitting messages is known as telegraphy.

Samuel Morse and his telegraphic code

T i l l the middle of the 19th century, news was sentfrom one place to another through letters and news-

papers carried by horse-drawn carriages, stage coachesand, where possible, by railway trains. These coacheswere slow and messages would take days, weeks or evenmonths to reach their destination.

With the advent of electricity, many scientists hadthought of the possibility of using it to send messagesquickly and several carried out experiments to that end.

But they did not succeed in their endeavours. The manwho did was not a scientist but a painter.

His name was Samuel Finlay Breese Morse (1791-1872). As a painter he enjoyed a good reputation inAmerica. Many distinguished men and women came

44


47/90

to him for their portraits. Even President Monroe hadhis portrait done by Morse. But few were to rememberhim as a painter.

After graduating from Yale, Morse told his father

45


48/90

of his desire to become an artist. His father was acongregational minister and he was rather disappointed.But he yielded to his son's entreaties and sent him toLondon to take lessons in painting. He was not able to

give him much money and Morse had to spend a fewyears in London in great poverty. Nevertheless, heworked hard and became a good painter.

Morse went to Italy in 1829 to acquaint himselfwith the artistic tradition of that country and the stylesof the great Italian painters. After a few years hedecided to return to America. On October 1, 1830, he

embarked on a vessel named Sully and set out on hisjourney home. The voyage not only changed Morse'scareer, but brought about a significant change in thehistory of human civilization.

At the dining table in the ship, some of Morse'sfellow passengers began to discuss electricity. Theytalked about the experimental efforts made to invent a

system to transmit messages by means of electricity.Several of them were learned in science and describedvarious instruments that were being tried.

Morse listened to their discussion with eager atten-tion. He knew very little about electricity. But as he satlistening to them he thought what a wondrous thing itwould be io be able to send messages instantly from one

end of the earth to the other. And it occurred to him,'Why can't I try just once? If I try, maybe I wouldsucceed in inventing telegraphy?'

He remembered the first letter he had written to hisfather and mother on reaching London: "Just as I sithere to write to you, a very strange and impracticableidea haunts my mindO, that my words would reach

you in an instant! I guess you are eagerly and impa-tiently waiting for my news and are ill at ease to thinkof my safety and well being. I am quite safe, hale andheartyO, if I could only convey these words to you

46


49/90

this very moment! But, alas! that is not to be! Thismessage of mine will take no less than four weeks toreach you."

Morse gathered as much information as he could

about electricity from his fellow passengers at thedining table. The more learned among them explainedto him matters related to electrical science and dis-cussed in detail the functions of the electric cell andelectromagnet.

Morse rose from the dinner table and went to hiscabin with an idea slowly taking shape in his mind. He

knew it was presumptuous of him to hope to succeedwhere specialists had tried and failed. But the ideapossessed him.

For days thereafter, he confined himself to hiscabin, thinking how he could test his own theory. Hedrew sketches of all the devices he thought of. Within afew days he could formulate a method of sending sig-

nals through a wire with a device using the magneticeffect of electricity.

Morse decided to pass an electric current, at requir-ed intervals, through a closed circuit in order to ener-gise an electromagnet which, by its actions, would bringa pencil into contact with a moving sheet of paper. Thepencil was to imprint dots and dashes produced by

electrical impulses of different duration.He devised an alphabetical code by a combination

of dots and dashes. Each of the different combinationsof these dots and dashes would symbolise a letter orfigure of the English alphabet and numerals. All theway to America, Morse sat in his lonely cabin thinkingof his telegraphic instrument. By the time his ship

berthed, he had invented what came to be known as theMorse Code.

On reaching America Morse became successful as apainter, but he refused many alluring offers so that he

47


50/90

Morse's first design for a telegraph apparatus.

could devote his whole time to his research. For a longtime he worked, with batteries, iron bars and levers.

But the road to success was not easy. The first instru-ment he devised did not work. He went on makingchanges and alterations in his apparatus till at last herealized his dream. He was able to send signals throughelectric wire from one end of his laboratory to theother.

For a public demonstration of his telegraphy, heneeded money, and that was not easy to get. Metallicwire was costly and he needed miles of it. The othermaterials required were also expensive. He could findno sponsors. Morse continued his experiments without

48


51/90

anyone to help him and soon became destitute.Then fortune smiled on him. A number of Senators

and influential men, realizing the importance of hisdiscovery, managed to get him a public grant for a

demonstration of his apparatus.A 40-mile-long cable was laid between Washington

and Baltimore. March 24, 1844, was the day set for thedemonstration before a group of experts selected by thegovernment. Morse sat in Washington, at the end ofhis telegraph line, and Vail, his assistant, at the otherend in Baltimore.

A tense, silent group watched as Morse took hisseat before his telegraph machine. When the machineproduced a sound, 'click, click, click', Morse began tosend this signal, in his own code: "What hath Godwrought?" Having transmitted his message, Morse lefthis seat.

Within seconds Morse's receiving apparatus came

to life. The pencil attached to the receiver began toprint on the paper, 'dot, dash, dash', representing theletter 'W'. And the entire signal, "What hath Godwrought?" was inscribed in code on the paper. Morsehad wrought a revolution in communication!

Shortly thereafter, cables were laid between severalcities in America. Later the telegraph system wasintroduced in other parts of the world as well.

It made its appearance in India in 1851, when thefirst telegraph cable was laid between Calcutta andDiamond Harbour.

Graham Bell invents telephone

T h e telegraph had come to be and scientists weretrying to improve on it. Among them was a young man

49


52/90

named Alexander Graham Bell (1847-1922). He wasstudying the possibility of sending through the teleg-raph line several messages at the same time.

Bell did not succeed in improving the system of

telegraphy. But he accidentally came by another brightpossibility. It occurred to him that, if sound could betransmitted as dots and dashes, the human voice couldalso be sent to distant places by electric cable.

Bell was born in Scotland. Both his father andmother were teachers of philology and phonetics.Along with his scientific studies, he also learnt much

about the tonal characteristics of the human voice, thedifferent sounds produced by such vocal organs astongue and lips.

His two brothers died of tuberculosis. When Bellshowed the symptoms of the same disease, his parentsdecided to take him to a healthier place. They leftScotland for Canada and settled in the city of Ontario.

Bell soon regained his health and went to Boston tojoin a school as teacher of philology. It was while hewas there that Bell became interested in telegraphy.

He set up a laboratory in two rooms at his houseand began to spend all his leisure hours with his friend,Watson, doing experiments. One day Watson wasworking a telegraph transmitter in one room of thelaboratory, while in the other room sat Bell with thereceiver. One of the metal plates of the transmitter wasnot working satisfactorily and Watson moved it backand forth a couple of times.

Hardly had he done so when Bell came rushing intoWatson's room excitedly and asked, "What were you

doing, Watson? I heard a clattering noise in my receiv-er!" Watson was astonished. He told Bell what he haddone.

"Do that again, Watson," cried Bell, rushing backto the telegraph receiver in the other room.

50


53/90

Watson again jerked the metal sheet to and fro.Instantly there was a clatter in Bell's receiver.

"Watson!" Bell shouted excitedly, "I bet we cansend any sound through a wire by means of electricity."

51


54/90

Bell found that, if a thin iron plate placed within amagnetic field was made to vibrate, the vibration woulddisturb the magnetic field. If such a thin plate ordiaphragm vibrated near an electromagnet, the inten-

sity of the field around it would wax and wane alter-nately. This was the principle Bell made use of in hisspeech machine.

When a man speaks before a transmitter, the dia-phragm placed near an electromagnet vibrates to thesound wave. And its vibration causes a fluctuation inthe magnetic field, inducing an electric current in the

wire wound about the magnet. This current, uponreaching a receiving apparatus, causes its diaphragm tovibrate by similarly fluctuating the nearby magneticfield. The nature of this electric current will depend onthe acoustic characteristics of the speaker's voice.

The electric current of a fluctuating intensity andfrequency generated by the transmitter is sent to the

receiver through another electromagnet. The vibrationcaused in the diaphragm of the transmitter by theimpact of a voice will produce exactly the same vibra-tion in another diaphragm placed within the receivingapparatus. That is how the diaphragm of the receivergenerates in the air a sound wave which is exactly thesame as the sound wave produced by the speaker'svoice.

On the basis of this theory, Bell and Watson triedfor years to invent an electric speech machine. Theirinitial efforts failed. Yet they continued their endeavourto improve their instrument. One day, again accident-ally, they achieved their objective.

That was on March 10, 1897. Bell was experimentingwith the transmitter of his speech machine in one roomand Watson was in the other room, sitting in front of areceiver. The door between the two rooms was shut. OnBell's table lay a voltaic battery. In a careless moment,

52


55/90

Bell's magnetic telephone.

the battery turned over and toppled from the table.Some acid spilt on the floor and stained Bell's clothes.

"Mr. Watson, come here at once," Bell shouted.As the door between the rooms was closed, Watsoncould not have heard Bell's shout directly. However, heheard it clearly. The sound had come from the receiver!

Astonished and excited, Watson rushed into theadjoining room and cried out, "Mr. Bell, your speechmachine is working. I heard your voice over thereceiver!"

Bell had invented the telephone. But again it was al-most by accident that the invention came to the world'snotice. On the anniversary of American Independence,a great exhibition was arranged at Philadelphia.

53


56/90

Among the exhibits on display was Bell's telephone.The day on which the exhibits were to be judged and

selected for awards was a Sunday. That day specialguests were allowed to attend the exhibition. Amongthem was Don Pedro, Emperor of Brazil, who was on atour of America. The judges walked about looking atthe things displayed in different stalls.

Time passed by and, in the heat of summer, allgrew tired. Bell realized that it would not be possiblefoi the judges to see everything at the exhibition. They

would not have time even to look at his telephone.Disappointed, he was about to leave the exhibitionwhen he heard a voice calling, "Mr. Bell!" He turnedand saw the Emperor stepping towards him with asmile on his face.

Years earlier, Emperor Pedro had visited the schoolin Boston where Bell was a teacher. There, for a long

time the two had discussed matters concerning educa-tion of the dumb. The Emperor remembered Bell.

Bell showed him his invention and the Emperorbrought it to the judges' attention. They were asimpressed with the apparatus as the Emperor.

One by one, all of them tried it. Thereafter thejudges had nothing, to judge, nothing to decide. Bell's

telephone was awarded the first prize.Calcutta again has the distinction of being the first

city in India to introduce the telephone system. A50-line exchange was established in Calcutta in 1881,about 30 years after telegraphy made its debut.

Michael Faraday and his discoveries

It was the voltaic battery that made Bell's inventionpossible. But the power a voltaic battery yielded was

54


57/90

limited. In the industrial field, man had to explore othermore powerful sources of electricity. A high-powergenerator of electricity was made possible on the basisof a theory propounded by Michael Faraday (1791-

1867).Faraday was born in a poor family. So, even at a

tender age, Faraday had to go out in search of a living.He got himself appointed as a page boy in a book stall.Fortunately, his master, Ribean, was kind. After abouta year, he took Faraday as a paid apprentice in thetrade of book binding.

But Faraday was more interested in the contents ofa book than its cover. He had a great fascination forscience. The boy read all the books on physics andchemistry that came to him for binding.

One day, one of their clients was talking to Ribeanabout the brilliant lectures Sir Humphrey Davy wasdelivering on electricity. Faraday happened to be

standing nearby."Mr. Ribean," said the client, "I am going to attend

Davy's lectures. I have an extra ticket. You may comewith me."

"Thank you", Ribean replied. "But I know nothingabout science and so will not be able to enjoy lecture onmatters of science." Then, pointing to Faraday, he said,

"Take this boy with you. He loves science. And he hasread all the books on electricity that I have in my shop."

Faraday's eyes sparkled as he looked at Ribean."All right, I shall take the boy with me," he said.Faraday was delighted to have this unexpected

opportunity to hear the lecture of a renowned scientist.That day, and on three other subsequent evenings, he

listened to Davy's lectures. He took notes on each and,in his spare time, recorded the details of the lectures.Having set down the notes with his own comments oneach point, he bound them into a volume.

55


58/90

After Faraday's apprenticeship was over, he founda j ob as book-binder. But his new master was not askind and sympathetic as Ribean. Faraday found thathe had neither the time nor the opportunity to study as

56


59/90

before. Annoyed with the rudeness of his new master,he decided to give up book-binding. But he had to findanother job.

Suddenly he remembered Humphrey Davy. But

what would an eminent scientist like Davy have to dowith a poor book-binder like him? After ruminatingfor some days, he decided to try his luck.

He wrote to Davy. With his letter he sent the boundvolume of the notes and comments he had made on thefour lectures he had attended. Days, weeks and monthspassed, but there was no response from Davy. Faraday

was disappointed. 'Why should a great scientist likeDavy bother about a letter written by a poor youngman like me?' he asked himself.

On December, 1812, on Christmas Eve, a coachcame and stood before Faraday's place of work. A manalighted and enquired about Michael Faraday. WhenFaraday came out, the man handed him a letter. With

trembling hands, he opened the envelope and read theletter.

It was more a note than a letter. But, what a wealthof joy it brought to his sad and weary hear t! It wasfrom Davy and it said: "The proof you have given meof your self-confidence and your tenacity of purposehas made me glad. This testifies to your zealous interest,

your fine memory and your great attentiveness. I amgoing out of London for some days and I shall not beable to come back and settle down here before the endof January. Any time thereafter, I shall be eager tomeet you. It shall give me immense pleasure to be ofany help to you. I wish it would be within my power."

Towards the end of January, soon after his returnto London, Davy sent word to Faraday, asking him tocome and see him at the Royal Institution. Faradaymet him, but Davy gave him no promise.

Faraday was again in despair. Was he destined to

57


60/90

remain a book-binder all his life? But about a monthlater, he received another letter from Davy saying thatFaraday could, if he wished, join the Royal Institutionas an assistant. Faraday joyously accepted the offer.

Davy had made many significant contributions tothe science of electricity. But his best contribution was,

perhaps, the opportunity he gave to Faraday to workat the Royal Institution. Davy himself was aware ofthis. Once a journalist asked him, "What, in yourown opinion, is your greatest discovery?"

"It is Michael Faraday," was the prompt reply.

Faraday had to perform many jobs apart from hisroutine duties. He had to keep the laboratory instru-ments clean and be at the beck and call of his superiors.But he was happy to have the opportunity to work inan environment of his choice. Now he could devotemuch time to his studies and experiments.

The subject of electromagnetism excited his special

interest after he learnt about the work and achieve-ments of Oersted and Ampere. He repeated, in his ownway, the experiments of the two great scientists andmade other experiments to test his own ideas.

Davy was greatly impressed by Faraday's devotionand irgenuity. He began to guide Faraday in research.As days passed by, Faraday's reputation grew. Fromthe post of laboratory assistant, he was raised tomembership of the institution. After Davy's death in1829, Faraday continued his researches and experi-ments independently.

A particular idea began to haunt his mind. Ifelectricity could produce magnetism, why cannot

magnetism produce electricity? In 1831, in the courseof an experiment, Faraday realized that he was notwrong in his assumption. He observed that an electriccurrent was induced in a coil of wire placed within afluctuating magnetic field. The discovery was of

58


61/90

immeasurable significance. Based on this principleelectric generators capable of producing immenseelectric power came to be made.

Sir Robert Peel was Prime Minister of Britain at

that time. Faraday had occasion to explain to Peel theprinciple underlying his electrical theory. He gave ademonstration as well. He connected a galvanometerto a coil of wire and showed that, if a bar magnet wasswung round the coil, the needle of the galvanometeralso swung in response to the movement of the magnet.But that made no impression on Peel- He commented

in a disparaging tone, "I have just seen that a needlemoves when a magnet is moved about. But what usefulpurpose will this discovery of yours serve our country?"

In reply Faraday only said, "No one can foretellwhat a newborn baby will grow up to be. Even so, mydiscovery may, some day, accomplish the impossible.It may be that, by making practical use of my inven-

tion, your government will, in the near future, realizea large amount of money by way of taxes from thepeople of this country."

It was not long before Faraday's prophecy came tobe fulfilled. The generators or dynamos by whichelectrical energy is produced nowadays work onFaraday's principle of electromagnetic induction. Apartfrom this theory, he made several other significantcontributions, especially his principles of electrolysis.

In the history of electrical science, 1831 is a signi-ficant year. That was the year in which Faraday foundthe process of electromagnetic induction. The sameyear, Joseph Henry, a teacher of Albany Academy,

New York, made the same finding on his own. Formany years he had worked to improve the electro-magnet. The electromagnet he built for the YaleCollege laboratory was so powerful that it could lift1600 kilograms and that too by means of electric

59


62/90

current obtained solely from a voltaic battery!There is difference of opinion about who first built

an electric generator or a dynamo. According to somethe credit goes to Faraday. Others say it should go to

Henry.In modern times a huge amount of electric power is

being used to operate various machines, to drive elec-tric trains and trams, to light houses and streets.Modern power houses are equipped with enormousgenerators driven by turbines which are rotated by thepressure of steam or water.

Steam turbines are now being used to drive thermo-electric generators, while, in the hydro-electric centres,the armatures of the generators are rotated by waterturbines.

In steam turbines, coal is burnt to heat water in aboiler and turn it into steam. The steam is directed byjets against blades of the turbine. The pressure exertedby the steam, kinetic pressure as it is called, sets theturbine in motion.

In the thermo-electric system, only a portion of thetotal mechanical energy applied to the turbine of thegenerator is converted into electrical energy. In ahydro-electric generator, it is the pressure of water that

rotates the turbine.

Thomas Alva Edison (1847-1931)

Generation of electricity was no longer a problem.

But it was yet to be brought to the house to be thecommon man's genie. The man who did that wasThomas Alva Edison.

Edison was born in Milan, Ohio (America), onFebruary 11. Though he became one of the greatest

60


63/90


64/90

inventors the world has ever seen, he received littleor no formal education. He attended primary schoolfor only three months or so. His mother took him outof the school when she heard that one day his teacher,after beating and scolding him, had said, "You are averitable dunce. You will do nothing in life."

Edison's mother, a teacher herself, started educatinghim. The result was astonishing. Edison grew more andmore attentive to his studies. With unusual eagernessand interest he began to learn many subjects.

When he was only 12, he began to look for a job.A new railway line had just been laid between PortHuron and Detroit and Edison applied to the railwayauthorities for permission to sell newspapers and foodto passengers.

As Edison was very young, his application wasrejected. But he was persistent and, at last, was

given permission to be a vendor. Not only couldhe earn a good deal, but also find much time for hisstudies.

As the train usually stopped at Detroit for five orsix hours, he became a member of a public librarythere. He began reading books on various subjects.What interested him most was chemistry. He made up

his mind to be a chemist.This meant that he had to do experiments. With the

permission of the train conductor, he set up a labora-tory in a luggage van. All went well till one day a bottlefilled with chemicals tumbled down and the van caughtfire. At this the conductor flew into a rage and threwaway all the chemicals and instruments in the labora-

tory. It was no longer possible for Edison to have alaboratory in the train. So he set up one at home, andresumed his experiments.

Edison also got interested in telegraphy. Once heasked a telegraph operator, "Can you tell me how, in

62


65/90

this telegraph system, a message is conveyed through awire?"

The operator said, "Suppose the telegraph line is adog with a very, very long body and the distancebetween its head and its tail is a few hundred miles.Now, when somebody pulls at the dog's tail, its headbegins to bark. That is how a message goes from oneend to the other end of the cable."

Edison asked, "Well, but how does the signal comefrom the tail up to the head?"

The operator grew annoyed and said, "Nay, I cantell you no more about it."

But there were books and magazines to give Edisonmore reliable information about telegraphy and he readall he could. He also laid a telegraph line between hishouse and a friend's. After a long trial the two friendssucceeded in exchanging messages through the wire.

When he was barely 16, he did a heroic deed thatbrought him the chance to become better acquaintedwith telegraphy. His train had stopped at a waysidestation and he was standing on the platform when henoticed a boy of two or three playing on the railwaytrack. He was in imminent danger of being run over bywagons that were being shunted on the line. Edison

flung himself on to the track, picked up the child andmanaged to jump clear with hardly a second to spare.The boy's father happened to be the telegraphoperator at the station and on learning of Edison'sinterest in telegraphy, offered to teach him.

Edison readily accepted the offer and within threemonths became an expert telegrapher. He gave up the

job of vendor and got himself employed as a part-timetelegraphist. Later he was posted as operator at Strat-ford, Canada. Edison was happy with his new job.Having been put on the night shift, he had all day tocontinue studies and experiments.

63


66/90

To make sure that the night operators stayedawake, the authorities had ruled that each should senda code message to the head office every half an hour.For Edison, the code signal was the number six in

Morse. Edison found this annoying and soon made adevice to transmit automatically his code number tothe head office at the required intervals. It worked well.Before long, the matter became an open secret. And thetelegraph authorities were not amused, even if theoperators were. Edison had to leave the job. As therewas a great demand for good telegraphists, it was easy

for him to find employment elsewhere. But the workwas not interesting and during the next five years hechanged jobs.

At the age of 22 he went to New York. One day,while looking for a job, he went to the office of the GoldReporting Telegraph Company. Work there had beendisrupted because the telegraph equipment had brokendown. As the business of the company was to send outand receive the ever-fluctuating bullion prices, theowner was desperate. No one seemed to know how toset the instrument right. Edison saw that it was a specialtype of instrument, not like any he had used. But hewas never lacking in confidence and he offered torepair it.

The owner, Laws, looked at the young man withmisgiving. Since he had no choice, he asked Edison todo what he could. It took Edison only a few minutes tolearn how the machine worked and he set it right.Laws employed him on the spot on a salary of 300dollars a month to keep the telegraph machine in order

and to try to improve it.Edison liked the job. The pay was good and it gave

him time to do his own research. He made alterationsto make the instrument work better and receivedseveral patents for his discoveries. Soon he was recog-

64


67/90

Edison's first electric bulb.

nized not only as one of the greatest inventors of tele-graphy but also as a great specialist in electrical science.By selling some of his patents he became a wealthy man.

With money no longer a problem, Edison left his

job and set up a laboratory and workshop at New-ark, New Jersey. He invented various instrumentsand made them in his workshop.

In 1874 Edison made up his mind to concentrate oninvention rather than manufacture. He left Newark

65


68/90

and settled in a village, Menlo Park, where he built amansion and set up a well-equipped laboratory. MenloPark was about an hour's journey by train from NewYork and Edison thought that the peace and quiet ofthe countryside would be ideal for his scientific pursuits.

Scientists were then trying to make an electric lamp.They had noticed that when an electric current wassent through a wire of high resistance, it generatedheat. The wire itself became hot. If the temperaturerose beyond a certain limit, it glowed.

Ten years after moving to Menlo Park Edisonstarted his own experiments. He let an electric currentflow through a thin, thread-like wire of platinum. Thefilament heated up and began to glow. But only

story of electricity

Documents