University of Cebu Lapu-Lapu and MandaueA.C Cortes Ave. Looc, Mandaue City

S.Y 2011 – 2012

Chapter summary of physics 2(1 - 9)

Submitted by:Chestere Eube I. Baring

Submitted to:Mr. Cariquitan

Chapter 1 Electrostatics

Electrostatics is the branch of physics deals with the phenomena arising from what seem to be stationary electric charges. It involves the buildup of charge on the surface of objects due to contact with other surfaces.

Physicists Inventors:

William Gilbert (1544-1603) . an early investigator of what we now called Electrostatics, which is the study of electric charge at rest. He made a sensitive instrument from a lightweight stick pivoted about its center on a needle point. He found that, if he rubbed a piece of amber and held it near the end of a stick, the stick moved noticeably about its pivot, indicating an attraction by the amber. He tried again rubbing other objects and found that many of them produced similar effects. In this way, Gilbert found a force that was present only after the amber or other substances was rubbed. This force was due not to gravitation, but to a different source, electricity.

Francis Hauksbee (1705). He developed the first true frictionless electric machine. The machine was consisted of a glass sphere turned by a crank. When he rubbed, the sphere was capable of making sparks and causing light threads to stand out from each other.

Stephen Gray (1731) . He found out that he could conduct electric charge over a great distance through a metal wire supported by silk cords. The observation led to the classification of materials into two types, the conductor and insulator.

Charles – Francois du Fay (1733) he found out that while two pieces of rubbed glass repelled each other and two pieces of rubbed amber repelled each other , the rubbed amber was strongly attracted to rubbed glass. His experiments provided evidence for two kinds of electric charge and for the basic rule of describing their behavior : like charges repel and unlike charges attract.

Benjamin Franklin (1706 - 1790) his kite experiment demonstrated that lightning is electricity. He was the first to use the terms positive and negative charge . franklin was one of the seventeenth children. He quite shool at age ten become a printer. His life is the classic story of a self – made man achieveing wealth and fame through determination and intelligence.

James watt (1736 -1819) was born in scotland. Although he conducted no electrical experiments , he must not be overlooked. He was an instrument maker by trade and set up a repair shop in Glasgow in 1757. Watt measeured the rate of work exerted by a hore drawing rubbish up an old mine shaft and found it amounted to about 22,000 ft lbs per minute.

William Thomson , Lord Kelvin (1824 - 1907) was best known in his invention of a new temperature scale based on the concept of an absolute zero of temperature at – 273 degree Celsius. To the end of his life, Thomson maintained fierce opposition to the idea that energy emitted by radioactivity came from the atom.

Thomas Seebeck (1770 - 1831) a German physicist was the one discovered the “Seebeck effect”. He twisted two wires made of different metals and heated a junction where the two wires met. He produced a small current. The current is the result of a flow of heat from the hot to the cold junction this is called thermoelectricity. Thermo is a Greek word meaning heat.

Michael Faraday (1791 - 1867) an Englishman, made one of the most significant discoveries in the history of electricity. Electromagnetic induction, His pioneering work dealt with how electric currents work. Many inventions would come from his experiments, but they would come fifty to one hundred years later.

James Maxwell (1831 - 1879) a Scottish mathematician translated Faraday’s theories into mathematical expressions. Maxwell was one of the finest mathematicians in history. A Maxwell is the electromagnetic unit of magnetic flux, named in his honor. Today he is widely regarded as secondary only to Isaac Newton and Albert Einstein in the world of Science.

Thomas Alava Edison (1847 - 1931) was one of the most well known inventors of all time with 1093 patents. Self educated, Edison was interested in chemistry and electronics. During the whole of its life, Edison received only three months of formal schooling, and was dismissed from school as being retarded.

Nikola Tesla was born of Siberian parents July 10, 1856 and died a broke and lonely man in New York City January 7, 1943. He envisioned a world without poles and power lines. Tesla’s system triumphed to make possible the first large – scale harnessing of Niagara falls with first hydroelectric plant in the United States in 1886.

George Westinghouse (1846 - 1914) was awarded the contract to build the first generators at Niagara falls. He used his money to buy up patents in the electric field. One of the invention he bought was the transformer from William Stanley. Westinghouse invented the air brake system to stop trains.

Alexander Graham Bell (1847-1922) born in Scotland, was raised in the family that was interested and involved in the science of sound. Bell’s father and grandmother both taught speech to the deaf. A unit of sound level is called a bel in his honor. Sound level are measured in tenths of a bel, or decibels. The abbreviation of decibel is dB.

Heinrich Hertz (1857 - 1894) a German physicist , laid the ground work for the vacuum tube. He laid the foundation for the future development of radio, telephone, telegraph, and even television. He was one of the first people to

demonstrate the existence of electric waves. Hertz was convinced that there were electromagnetic waves in space.

Otto Hahn (1879 - 1968) a German chemist and physicist, made the vital discovery which led to the first nuclear reactor. He uncovered the process of nuclear fission by which nuclei of atoms of heavy elements can break into smaller nuclei, in the process releasing large quantities of energy. Hahn was awarded the Nobel prize for chemistry in 1994.

Albert Einstein (1879 - 1955) Einstein’s formula proved that one gram of mass can be converted into a torrential amount of energy. The activity of atoms has to occur in the nucleus. E = energy, M = mass, C = speed of light which is 186,000 miles per second.

Generalization of the Physicist/Scientist:I realized that because of the physicists, people before

and in present, used their inventions and their contributions in order for us to subsequently solve the problems we had in terms of Scientific approach. Because of their inventions, technology in the world, innovates so fast. Their contribution is long lasting. In which, it is learned and acquired from generation to generation. Without them, I think, we cannot easily solve the problems we encounter each day.

About Atoms:Everything in the universe is made up of atoms. Every

stars, every tree, every animal. The human body is made up of atoms. Air and water are too. Atoms are the building blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.

The Center of the atom is called nucleus. It is made of particles called proton and neutrons. Protons and neutrons are very small, but electrons are much, much smaller. Electrons spin around the nucleus In shells a great distance from the nucleus.

Electricity has been moving in the world forever. Lightning is a form of electricity. It is electrons moving from one cloud to another or jumping from a cloud to the ground. A stream of electrons jumped to you from a object is called static electricity.

Coulomb’s Law of Electrostatic force:

Coulomb’s law states that “The electric force of attraction and repulsion between charges is directly proportional to the product of their magnitude and inversely proportional to the square of the distance between them.”

Formula:

F = kq1q2

r 2

Where: F = electrostatic force, Newton(N) or Kilonewton(kN) k = electrostatic constant with a value of 9 x 109 Nm2/C2

q1 = electrical charge of first particle, Coulomb(C) q2 = electrical charge of second particle, Coulomb(C) r = distance or separation

Formula derivation:

a. if the unknown is q1 F = kq1q2r 2

q1 = Fr2

kq2

b. if the unknown is q2

q2 = Fr2

kq1

c. if the unknown is r

r = √ kq1q2F

Generalization about atoms and the Coulombs law of Electrostatic Force:

I realized that, everything in universe are made of atoms. without atoms, there is no lightning, heat and power. Because, atoms is the building blocks of the universe, which gives convenient aspect form of energy that will be transmitted over much greater distances to every current. And to the Formulas given by Coulomb’s law of Electrostatic Force, I realized that, it is very significant for the application of the form of electricity. according to the Statement,

“Electrostatic force is directly proportional to the product of magnitude” it means that, the greater is the product of the magnitude of charges the greater the electrostatic force acting between them. The knowledge of every particles of matter, their charges in Coulomb and mass are very important.

Chapter 2

Electric Field

Electric field is the area around a charged Object. the field exerts a force on any charged object in the vicinity. the closer the charged object is brought to the charged object creating the field, the greater the force exerted on it.

Electric Field is defined as the electric force per unit charge. in mathematical expression, it is:

E = Fq

The direction of the field is taken to be the direction of the force it would exert as a positive test charge. the electric field is radially outward from a positive charge and radially in toward a negative point of charge.

a.) positive test charge b.) negative test charge

Important formulas of electric field:

Coulomb’s law: F = kq1a2

r 2

Electric Field : E = Fq

Derivation of formulas:

since: F = kq1q2

r 2 can substitute F as: E =

k q2

r2

q

Therefore, electric field also be computed using : E = kq

r2

where:

F = electrostatic force, Newton(N) or Kilonewton(kN)k = electrostatic constant with a value of 9 x 109 Nm2/C2

q1 = electrical charge of the first particle, Coulomb(C)q2 = electrical charge of the second particle, Coulomb(C)r = distance or separationE = Electric Field, Newton per Coulomb,(N/C)

a.) if the unknown is q

q = Er2

k

b.) if the unknown is r

r= √ kqEGeneralization of Chapter 2:

I realized that when an electric field is present somewhere, the properties of space around it are altered in such a way that another charge brought to this region will experience a force. And any other charge is considered to interact with the field and not directly with the charge that gives rise to it. I realized also that the field lines indicates the direction of the field, the field points in the direction tangent to the field line at any point.Also, Electric field lines start on a positive charge and end on a negative charge. And I have learned that the closer the lines are drawn together, the stronger the electric field is in that region.

Chapter 3Potential Difference and Electric current

Potential Difference: Potential Difference is a difference in the amount of attraction or repulsion between any two points in an electric field. Potential difference is measured in volts. when there is potential difference, charge flows from the higher potential to the lower potential. the flow of charge persist until both ends reach the same potential.

Voltmeter is used to measure the electric potential difference between two points in an electric circuit. it is connected in parallel across a load in the circuit. it has a very high internal resistance.

Important formulas:

V = wq W = F r V = E r I =

qt

where:

V = Voltage I = current t =time W = Work

q = charge F = Force E = Electric Fieldr = distance

Derivation of formulas for potential difference:we use these formulas,

a.) if the unknown is WW = V q

b.) if the unknown is q

q = WV

c.) if the unknown is V in the formula q = WV and q =

FrV

to solve for q.

V = Frq

d.) if the unknown is r or d;

r = VqF

Electric Current

Electric current is simply the flow of electric charge. in circuits of metal wires, electrons make up the flow of charge. This is because one or more electrons from each metal atom are free to move throughout the atomic lattice. These charge carriers are called conduction electrons.

Protons on the other hand, do not move because they are bound inside the nuclei of atoms that are more or less locked in fixed positions.

Electric current flows easily in some substances but not all in others. Solids, liquids, and gases are that carry electric currents are called conductors. The rate at which electric charge flows in a current is measured in amperes. the unit is named for French physicist Andre Marie Ampere, who contributed to the study of electrodynamics in the early 19th

century.

Derivation of formulas for electric current:

a.) if the unknown is q

I = qt

b.) if the unknown is I, combining the two formulas:I = Ne ¿¿

Generalization:I realized that, a fruit can also produce a potential

difference because of the two different electrodes made of different metals are pierced to it and the flow of charge takes place. Because of potential difference, each charged particle creates and electric field around it that attracts or repels other charged particles.

Chapter 4Resistance, Resistivity and Temperature

Resistance

Resistance is the property of any object or substance to resist or oppose the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage.

The term resistance is also used when the flow of a fluid or heat is impeded. The forces of friction provide the resistance to the flow of fluid pipe, insulation provides thermal resistance that reduces the flow of heat from a higher to a lower temperature.

Resistivity

Resistivity is an intrinsic characteristic of the material itself defined by a voltage divided by the density of current flowing across the material.

Formula:

R = ρLA

where:ρ = resistivityL = lengthA = cross sectional are

TemperatureTemperature is a physical property of matter that

quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot. Heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature, at a rate that increases with the temperature difference

and the thermal conductivity. No heat will be exchanged between bodies of the same temperature; such bodies are said to be in "thermal equilibrium".

To determine whether there is a change in the resistance of a wire when there is temperature change, use the mathematical formula:

RN = Ro(1 + α (ΔT ))where:

RN = New resistance, ohmsRo = Original resistance, ohmsα = temperature coefficient, / degree CelsiusΔT = Change in temperature (Tf - To)

Derivation of formulas:

Using the formula R = LA , we can derive the different

unknownsa.) if the resistivity is unknown

ρ = RAL

b.) if the length (L) of the wire is unknown

L = RAρ

c.) if the cross-sectional area (A) is unknown:

R = ρLA

ResistorsResistor, a component of an electric circuit that resists

the flow of direct or alternating electric current. Resistors can limit or divide the current, reduce the voltage, protect

an electric circuit or provide large amounts of heats or light.Generalization:

I realized / understand that resistance is used when the flow of a fluid or heat is impeded. while in resistivity, it determines the nature of resistance and the substance which its composed. And in Resistors, it limits the flow of the current to protect from electric circuit.

Chapter 5Ohm’s Law

Ohms Law, it is the relationship among voltage, current, and resistance is summarized. It defines the relationships between (P) power, (E) Voltage, (I) current, (R) resistance. One Ohm is the resistance value through which one volt will maintain a current of one ampere. This relationship was discovered by George Simon Ohm.

Ohm’s Law deals with the relationship voltage and current in an ideal conductor. this relationship states that: The potential difference (Voltage) across an ideal conductor is proportional to the current through it.

Derivation of formula for Ohm’s Law:a.) if the unknown is Voltage (V):

V = I Rb.) if the unknown is resistance(R):

R = VI

Generalization about Ohm’s Law:

My understanding about Ohm’s Law, it is significant to power, voltage, current, and resistance, through a

conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship. And now I understand that the unit of electrical resistance was named the ohm in his honor.

And George Simon Ohm’s formulation of the relationship between current, electromotive force, and resistance , is Ohm’s basic law of current flow.

Chapter 6Electrical Power

Electrical Power is the rate at which work is done that is, the rate at which electrical energy is converted into another from as mechanical energy, heat, or light.Electric power is equal to the product of current and voltage, or it is amount of the current times the voltage level at a given point measured in wattage or watts.

Important equations:

P = I V P = I 2R P =V 2

R P =

Wt

Derivation of formulas for Electrical power:P = power I = current V = voltage R = Resistance

P = IV; since current (I) is derived from I = VR , therefore,

substituting the current (I) given us:

P = VR (V) P = V

2

R

P = IV; since voltage (V) is derived from V = IR, therefore, substituting the voltage (V) given us:

P = IR (I)P = I 2 R

Generalization of Electrical Power:

I realized that, Electrical Power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. And if I will apply this to a device, Devices can be made that convert this work into heat (electric heaters), light (light bulbs and neon lamps), or motion. kinetic energy (electric motors).

Chapter 7Electrical Circuits

Electric Circuits is a path where electric current can pass through. the term is usually taken to mean a continuous path composed of conductors and conducting devices and including a source of electromotive force that drives the current around the circuit.

Circuit is any arrangement of materials which allows the flow of electric current. Circuit is composed of source of electrical energy, connecting wires of conducting wires, switch and a load. There are Two kinds of circuit:

Closed Circuit Open Circuit

Closed Circuit composed of source of electrical energy has a connecting wire of conducting wires, switch and load.

Open Circuit is the current path and it is not continuous. Short Circuit is a closed Circuit in which in a direct connection is made, with no appreciable resistance, inductance, or capacitance, between the terminals of the source of electromotive force.

Types of Circuits: Series Circuit Parallel Circuit Series – parallel Circuit

A Series Circuit is one in which the devices or elements of the circuit are arranged in such a way that the entire current (I) passes through each element without division or branching into parallel circuits.

when two or more resistances are in series circuit, the total resistance may be calculated by adding the values of such resistances is given by a formula.

Resistance:RT = R1 + R2 + R3 + R4

Whatever is the value of the total current that would also be the value of the current passing through each bulb. It means that the current in all points of the series circuit is the same.IT = I1 = I2 = I3 = I4 = …….

Parallel Circuit has more than one resistor (anything that uses electricity to do work) and gets its name from having multiple (parallel) paths to move along . Charges can move through any of several paths. If one of the items in the circuit

is broken then no charge will move through that path, but other paths will continue to have charges flow through them. 

if the resistance are in parallel, the total value of the resistance in the circuit is given by the formula:

1RT =

1R1

+ 1R2

+ 1R3

+ 1R4

+……. .

The current in each load is dependent on its resistance. In parallel circuit is not the same.

Series-Parallel circuit is simply the combination of series and the parallel circuit and with its basic principles. In the application of these concepts, we will be guided with the effect of the equivalent resistance in accordance to the individual resistance.

Generalization: I have learned that there are advantages in using series

circuit. it is easy to turn off simultaneously the entire circuitry. And the demand is less use of electrical materials during actual installation. while in using the parallel circuit, the use of a certain wire section would not disturb other electrical branch during actual use. And the demand may be lesser voltage source as the total resistance may decrease in any additional connection of such circuitry type.

Chapter 8Kirchoff Rules

Gustav Kirchoff formulated two rules that makes possible to find the current in each part of direct- current circuit. These rules applied to junctions, which are points where

three or more wires come together and the loop, which are closed conducting paths that are part of the circuit.

Loop and Junction Rule:

1. The sum of the currents entering any junction must equal the sum of currents leaving that junction. (A Junction is any point in the circuit where the current can split.) This rule is often called JUNCTION RULE.

(Sums of Currents into junction = sum of currents out of the junction)

2. The sum of the potential difference across each element around any closed circuit loop must be zero. This rule is usually called Loop Rule.

The first rule is a statement of conservation of charged. the algebraic sum of all currents flowing into the junction of a circuit equals the algebraic sum of the currents flowing out.

Junction formula:

VR1 =

VR2

+ VR3 I1 = I2 + I3

Generalization:

I understand about this chapter is that, if we encounter difficult or complex circuits, we can use a set of rules that will greatly simplify the procedures of analyzing the circuits through the use of Kirchoff’s Rules, the junction and the loop rule. In these rules, we can already conserve energy and at any point the potential drops.

Chapter 9Capacitors and Capacitance

Capacitors is a device that stores electrical charge on its conducting surface. A number of applications for this device can be traced in the assembly radio and televisions sets, electronic board or in an automobile ignition system. Some capacitors are made of parallel plates, separated by a piece of paper or other non-conducting materials. We can use these materials as dielectrics .

Dielectrics are insulators, plain and simple. When the conducting plates are connected to the terminals of a power source, negative charge is force onto one plate , leaving the other plate with a net positive charge. Furthermore, a capacitor with plates of larger area can store more charge compared to plates with smaller area. There are also significant effects when the plates are spaced either too close to each other or far apart.

Capacitance:It is the measure of the amount of electric charged

stores for a given electric potential. The most common form of charge storage device is a two plate capacitor. If the charges on the plates are +Q and –Q, and V gives the voltage difference between the plates, then the capacitance is given by:

Parallel Capacitance: CT = C1 + C2 + C3

Series Capacitance: 1CT =

1C1

+ 1C2 +

1C3

Uses of CapacitorsCapacitors are used for several purposes:

Timing – for example with a 555 timer IC controlling the charging and discharging

Smoothing – for example in power supply. Coupling – for example between stages of an audio

system and to connect a loudspeaker. Filtering – for example in the tone control of an audio

system. Tuning – for example in radio system. Storing energy – for example in camera flash circuit.

There are many different types of capacitors , ranging from ceramic capacitors , to electrolytic capacitors, and silver mica capacitors to various forms of plastics (polyester) capacitors.

Capacitor Types:There are many different types of capacitor that are

available today. Each has its own advantages and disadvantages and this means that it is necessary to choose the best capacitor for each use.

Ceramic Capacitor – as the name suggests, ceramic capacitors use ceramic as the dielectric between the plates of the capacitor.

Electrolytic Capacitor – this type of capacitor offers a very high level of capacitance per unit volume.

Plastic film Capacitor – there is a variety of types of plastic film capacitor, offering many different properties.

Silver mica Capacitor – as the dielectric and have silver plates. they offer a high degree of performance for radio frequencies and in particular plates.

Tantalum Capacitor – a form of electrolytic capacitor that uses tantalum based compound as the dielectric. it has exceedingly high level of capacitance per unit volume.

Generalization of Chapter 9:

I realized or understand about his chapter, Capacitor and Capacitance, is that Capacitance is also a measure of the amount of electric potential energy stored (or separated) for a given electric potential. A common form of energy storage device is a parallel-plate capacitor. In a parallel plate capacitor, capacitance is directly proportional to the surface area of the conductor plates and inversely proportional to the separation distance between the plates.