Secondary LevelsPHYSICS STUDYfor

Practical Book

Complete

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Complete Physics Study for Secondary Levels PRACTICAL BOOK is written with the aim of making Physics practical simple for students so that they will come out excellently at the end of any practical physics examination. Physics teaching instructions in senior secondary schools involve both theoretical and practical exercises in which psychomotor skills, acquirable from the subject are first learnt through observation of teacher’s demonstrations. These are then practised under the supervision of the teacher in a physics laboratory.Practical physics is pivotal to success in physics field. Unfortunately, many schools delay its teaching till the end of the second term of the SS3 class. Some schools do not even have the apparatus required for many of the experiments, even though few of the apparatus can be improvised. However, students’ performance in Physics could be improved tremendously if they are deliberately exposed to practical work and the acquisition of relevant skills right from the beginning of SS1 class. Various experiments have to be performed by making use of appropriate apparatus to generate data in tabular form. The data are then treated statistically through the use of graph in order to make necessary deductions.Complete Physics Study for Secondary Levels PRACTICAL BOOK is divided into four different units which are mechanics, optics, heat and electricity. Each of these units is further divided into different experiments. These divisions are very essential parts of practical physics in the senior secondary school. In addition, the book contains general introductory notes which the students must acquaint themselves with in order for them to have exciting experiences during the course of the experimentation.One of the added values of this book is that each experiment starts with the theoretical background of the concept to be verified. So, each experiment is tailored towards the provision of some of the basic training and techniques required in scientific experimentation and its presentation. Theoretical structured questions, which are based on each experiment and its concept, are included at the end of each experiment. In addition, graded past questions on mechanics, optics, heat and electricity, from examining bodies are selected for students’ assessment.Finally, physics knowledge is dynamic, so the experiments presented in this book are not the end of self-discovery and intuition. It is hoped that this book will serve its purpose of aiding the success of students in practical physics examinations.

Preface

Unit 1-Mechanics

Experiment 1(a): To measure length/thickness of various objects by using Vernier calliper,

micrometer screw gauge, Tape rule etc ................................................................................................................. 1

Experiment 1(b): To find the mass of the given body by using a beam balance .............................. 10

Experiment 1(c): To determine the weight of an object using a spring balance ............................. 13

Experiment 1(d): To measure the time of an event using a stopwatch ............................................... 18

Experiment 2: To determine acceleration due to gravity “g” using a simple pendulum ............... 22

Experiment 3: To determine acceleration due to gravity “g” using a compound pendulum ...... 26

Experiment 4: Verification of Hooke’s law of elasticity .............................................................................. 30

Experiment 5: To determine force constant of a spring ............................................................................. 34

Experiment 6: To study simple harmonic motion of a wooden block using a G-clamp ................ 38

Experiment 7: To determine the resultant of two forces using a force board ................................... 42

Experiment 8: To determine coefficient of friction between two surfaces ........................................ 45

Experiment 9: To verify the principle of moment (lever balancing) ..................................................... 49

Experiment 10: To verify Archimedes’ principle ........................................................................................... 53

Experiment 11: To determine relative density of a liquid, say, kerosene using the principle of

moments ............................................................................................................................................................................ 57

Experiment 12: To determine relative density of a given liquid by using Hare’s apparatus ...... 61

Experiment 13: To verify Boyle’s law ................................................................................................................. 64

Contents

Unit 2-Optics

Experiment 1: To verify the laws of reflection of light using a plane mirror ..................................... 68

Experiment 2: To determine the focal length of a concave mirror by using a Ray Box ................. 73

Experiment 3: To determine the focal length of a convex lens by using a Ray Box. ........................ 76

Experiment 4: To verify Snell’s law of refraction by using a rectangular glass block .................... 80

Experiment 5 and 6: To determine the angle of minimum deviation of a prism and hence,

find its refractive index ................................................................................................................................................ 84

Unit 3-Heat

Experiment 1: To demonstrate the convection currents in liquids ........................................................ 90

Experiment 2: To investigate the conductivity of water ............................................................................. 93

Experiment 3: To determine the melting point of naphthalene .............................................................. 96

Experiment 4: To demonstrate the effects of impurity on the boiling point of water ................... 99

Experiment 5: To determine the specific heat capacity of water by heat exchange method ... 102

Experiment 6: To determine the specific heat capacity of various solids by heat exchange

(mixture method) ....................................................................................................................................................... 105

Unit 4-Electricity

Experiment 1: To verify Ohm’s law by using ammeter-voltmeter method ..................................... 109

Experiment 2: To measure internal resistance of a battery ................................................................... 115

Experiment 3: To investigate the effect of varying the potential difference between two points

of a metallic conductor ............................................................................................................................................. 120

Experiment 4: To determine the value of a resistance using Metre Bridge ..................................... 126

Experiment 5: To study the relationship of potential difference across wire and length of the

wire by using a potentiometer .............................................................................................................................. 132

Experiment 6: To measure the resistance of a coil by heating effect of electric current ........... 137

Graded Examination Questions for Practice ............................................................................................ 141

Natural Trigonometric Functions ................................................................................................................... 162

Common Logarithms .............................................................................................................................................. 164

Exponential Functions .......................................................................................................................................... 167

Units and Symbols ................................................................................................................................................... 168

Table of Physical Constants ................................................................................................................................ 170

Answers of MCQs and Theoretical Questions Based on Practical ................................................ 174

Index ................................................................................................................................................................................ 201

Unit

INTRODUCTIONIt is very important to have a precise and accurate measurements of various physical quantities in the scientific world. Length is one of the seven fundamental quantities and it can be measured with a number of instruments like Vernier calliper, Micrometer screw gauze, Meter rule, Tape rule etc. Most of us have heard about tape rule which is used to measure the length of any object.Vernier calliper and Micrometer screw gauze measure the length more precisely as compared to a Metre rule or a Tape rule with reading error of about 0.05 mm and 0.01mm respectively. Vernier calliper was invented by Pierre Vernier (Fig. 1a). He was a French mathematician who is known for introducing this device for accurate linear measurements. Micrometer screw can measure up to 3 places of decimals. It was invented by William Gascoigne (Fig. 1b). He was an English astronomer, mathematician and maker of scientific instruments.

Aim of the ExperimentTo measure length/thickness of various objects by using Vernier calliper, micrometer screw gauge, Tape rule etc.

ApparatusVernier calliper, screw gauge, spherical body or a cylinder, a card board sheet

TheoryA Vernier calliper [Fig. 4(a)] consists of two graduated scales. A main scale which is graduated similar to a normal ruler and a Vernier scale which can slide along the main scale. The Vernier calliper is mainly used for measuring diameters of objects, both internal and external. The technique for measurement is to first read the main scale to the nearest division. Then, the Vernier scale is used to measure the distance between the two main scale divisions which provides more accurate measurements.Let n Vernier scale division (VSD) coincide with (n – 1) main scale divisions (MSD). Then,

n VSD = (n – 1) MSD1VSD = [(n – 1) / n] MSD

1MSD – 1VSD = 1MSD – [(n – 1) / n] MSD = (1 / n) MSD

Mechanics1

Experiment 1(a)

Fig. 1(a) Pierre Vernier

Fig. 1(b) William Gascoigne

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The difference between the values of 1MSD and 1VSD is known as Vernier Constant (VC) or the least count (LC). This is the smallest distance that can be accurately measured with the help of Vernier scale. Thus,

VC = LC = 1 MSD - 1VSD = (1 / n) MSDL.C. = Smallest division on main scale / Number of division on Vernier scale

In the ordinary Vernier calliper 1 MSD is 1 cm and there are 10 VSD.When an object is kept between the jaws of a Vernier calliper to measure its length, there are two things which are noted.Main scale reading (MSR) = Reading on the main scale coinciding with the zero of the Vernier scale (in cm).Vernier scale reading (VSR) = (Division on the Vernier scale other than zero which is coinciding with any division on the main scale) × LCLength of the object = MSR + VSRZero Error and Zero Correction: Usually, in a Vernier calliper, the zero of the main scale coincides with the zero of the Vernier scale as shown below and we say that there is no zero error in such a case.

Positive error: When the two jaws are in contact and the zero of the Vernier scale lies right to the zero of the main scale, the error is positive and the zero correction is negative. So, we need to find the division on the Vernier scale which coincides with any division on the main scale and multiply it with the least count (LC). For example, in the below figure, we can see that the third division on the Vernier scale coincides with any division on the main scale, then

Positive Zero error = + 3 × (LC) = 3 × 0.01 cm = 0.03 cmand Zero correction = − 3 × (LC) = − 3 × 0.01 cm = − 0.03 cmSo, whatever reading will be taken, – 0.03 cm will be added to it to get the correct reading.Negative error: When the two jaws are in contact and the zero of the Vernier scale lies left to the zero of the main scale, the error is negative and the zero correction is positive. So, we need to find the division on the Vernier scale which coincides with any division on the main scale,

Fig. 2(a)

Fig. 2(b)

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subtract it from 10 and multiply it with the least count (LC). For example, in the below figure, we can see that the eighth division on the Vernier scale coincides with any division on the main scale, then

Negative Zero error = – (10 – 8) × (LC) = –2 × 0.01 cm = − 0.02 cmand Zero correction = + (10 – 8) × (LC) = + 2 × 0.01 cm = + 0.02 cmSo whatever reading will be taken, + 0.02 cm will be added to it to get the correct reading.Screw Gauge: A micro meter screw gauge [Fig. 4(b)] is an instrument used for measuring the diameter of a thin wire or the thickness of a metal sheet or any glass plate. It consists of a U-shaped frame fitted with a screwed spindle which is attached to a thimble. Parallel to the axis of the thimble, a scale graduated in mm is engraved. This is called main scale. It is graduated similar to a normal ruler A sleeve is attached to the head of the screw.The head of the screw has a ratchet which prevents undue tightening of the screw. On the thimble, there is a circular scale known as head scale which is divided into 50 or 100 equal parts or divisions. When the screw is working, the sleeve moves over the main scale. A stud with a plane end surface called the anvil is fixed on the ‘U’ frame exactly opposite to the tip of the screw. When the tip of the screw is in contact with the anvil, usually, the zero of the main scale coincides with the zero of the circular scale.We generally define two terms related to a micro meter screw gauge.

Pitch of the screw = No. of full rotation given

Distance moved by screw ………(1)

Least count = Total number of divisions on the circular scale

Pitch ………(2)

Generally, the pitch of a screw gauge is 1 mm or 0.1 cm and there are 100 divisions on the circular scale.When an object is kept between the Anvil and the screw of a Screw Gauge to measure its length or thickness, there are two things which are noted.Main scale reading (MSR) = Reading on the main scale (in cm)Circular scale reading (CSR) = (Division on the Circular scale other than zero which is coinciding with the base line of the main scale) × LCLength of the object = MSR + CSRZero Error and Zero Correction in a Screw Gauge: Usually, in a Screw Gauge, the zero of the circular scale, coincides with the base line of the main scale as shown below and we say that there is no zero error in such a case as shown.

Fig. 2(c)

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Positive error: When the zero of the circular scale, is below the base line of the main scale as shown in the figure below, the zero error is positive and the zero correction is negative. So, we need to find the division on the Circular scale which coincides with the base line on the main scale and multiply it with the least count (LC). For example, in the figure below, we can see that the second division on the Circular scale coincides with base line on the main scale, then

Positive Zero error = + 2 × (LC) = + 2 × 0.001 cm = + 0.002 cmand Zero correction = − 2 × (LC) = − 2 × 0.001 cm = − 0.002 cmSo, whatever reading will be taken, – 0.002 cm will be added to it to get the correct reading.Negative error: When the zero of the circular scale is above the base line of the main scale as shown in the figure below, the error is negative and the zero correction is positive. So, we need to find the division on the Circular scale which coincides with base line on the main scale, subtract it from 100 or 50 (number of circular scale divisions) and multiply it with the least count (LC). For example, in the figure below, we can see that circular scale has 50 divisions and the 46th division on the Circular scale coincides with the base line on the main scale, then

Negative Zero error = – (50 – 46) × (LC) = – 4 × 0.001 cm = − 0.004 cmand Zero correction = + (50 – 46) × (LC) = + 4 × 0.001 cm = + 0.004 cmSo, whatever reading will be taken, + 0.004 cm will be added to it to get the correct reading.

Fig. 3(a)

Fig. 3(b)

Fig. 3(c)

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Diagram

PROCEDURE 1. Determine the least count of Vernier calliper/Screw Gauge and record it. 2. Find the zero error if any. If there is no zero error, then record zero error, as Nil. 3. Place the object between the two jaws or between the anvil and spindle and adjust them,

such that they gently grip the body without any undue pressure on it. 4. Note the number of divisions on the main scale of Vernier calliper/screw gauge. This

reading is called main scale reading (MSR). 5. Note the number of divisions of Vernier scale coinciding with any division on the main

scale /circular scale which are coinciding with the base line of the main scale. 6. Repeat the steps 3, 4, 5 for different positions and record the observation in the observation

table. 7. Apply zero correction in each case and complete the observation table.

For Vernier calliper:

OBSERVATIONSDetermine of Vernier constant (Least count) of Vernier calliper • 1M.S.R = 1mm = 0.1 cm 10 V.S.D = 9 M.S.D 1 V.S.D. = 0.9 M.S.D = 0.9 mm = 0.09 cm V.C = 1 M.S.R – 1 V.S.R = (1 – 0.9)mm = 0.1 mm = 0.01 cm • Zero error = …………… cm • Zero correction = …………… cm

Fig. 4(a)

Fig. 4(b)

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Measuring tips (for internal diamension)

Measuring tips (for external diamension)

Main scale (fixed scale)

Vernier scale (movable scale)Clamping screw

Movable jawFixed jaw

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U-frame

Base line

Sleeve

Main scaleNut

ScrewAnvil

Spindle

Thimble

Ratchet

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Observations Table

S. No.

Main Scale Reading M.S.R.

(cm)

No of V.S.D(n)

Vernier Scale Reading

V.S.R = n × V.C (cm)

Length =M.S.R + V.S.R

(cm)

Corrected Length L

(cm)

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CALCULATIONS

Mean corrected length

L = L L L L L1 2 3 4 5

5

+ + + + = ………… cm

RESULTThe length of the given object is ……………… cm

For Screw Gauge:

OBSERVATIONS • 1 M.S.R = ………. mm = …………..cm Number of divisions on circular scale = ………… No of rotations given to the screw = ……………. Pitch = distance moved by the screw / no of rotations = …………. cm Least count = Pitch / no of circular scale divisions = …………….. cm • Zero error = ……………cm • Zero correction = ……………cm

Observations Table

S. No.

Main Scale Reading M.S.R.

(cm)

No of C.S.D(n)

Circular Scale Reading

C.S.R = n × V.C (cm)

Thickness =M.S.R + C.S.R

(cm)

Corrected thickness t

(cm)

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CALCULATIONS

Mean corrected thickness

t = t t t t t1 2 3 4 5

5

+ + + + = ………… cm

RESULTThe thickness of the given object is ……………… cm

PRECAUTIONS 1. Ensure that the Vernier or circular scale is able to slide smoothly over the main scale. 2. Ensure that the zero error is carefully noted and properly corrected. 3. Ensure that the body is gripped between the jaws firmly but gently with not much

pressure on it. 4. Ensure that there is no parallax error while noting down the readings on vernier calliper/

screw gauge.

EXTENDED ACTIVITIES 1. To find the internal volume of a beaker using a Vernier calliper. 2. To find the volume of a cube by measuring its length, breadth and height using a Vernier calliper. 3. To find the thickness of an aluminum foil using a screw gauge.

M ultiple Choice Questions (Practical Based) 1. In a Vernier calliper, 20 divisions on the Vernier scale coincide with 19 small divisions

of the main scale. If one centimeter on the main scale is divided into 20 equal parts, the Vernier Constant is

(a) 0.05 mm (b) 0.025 mm (c) 0.005 mm (d) 0.25 mm 2. In a Screw Gauge, the zero line of the circular scale is 4 divisions below the line of

graduation, when the gap between the stud and the screw is zero. When it was used to find the thickness of a sheet, the observed reading is found to be 0.137 cm. The corrected reading is

(a) 0.141 cm (b) 0.137 cm (c) 0.133 cm (d) 0.004 cm 3. The below diagram shows the cross-section of a screw gauge while noting down the

thickness of a card board sheet. The observed reading (in cm) is:

(a) 0.455 cm (b) 0.355 cm (c) 3.55 cm (d) 0.0355 cm 4. The ratchet is (a) to maintain optimum pressure (b) a frictionless pulley (c) to avoid back lash error (d) for measuring least count

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5. An instrument with negative zero error reads (a) less than the actual value (b) more than the actual value (c) equal to the actual value (d) negative of the actual value 6. The following diagram of a Vernier calliper shows which kind of error

(a) Positive Error (b) No error (c) Negative Error (d) Back lash error 7. Vernier constant is (a) difference between one main scale division and one Vernier scale division (b) pitch / no of Vernier scale divisions (c) reciprocal of Vernier scale divisions (d) both a and b

T heoretical Questions Based on Practical Q1. In a Vernier calliper, 10 divisions on the Vernier scale coincide with 8 small divisions of

the main scale. If one centimeter on the main scale is divided into 10 equal parts, find its Vernier Constant.

Q2. A screw gauge is used to find the thickness of a wire as shown below. The least count is given to be 0.001 cm. The observed thickness (in cm) is

Q3. In a screw gauge, there are 50 divisions on the circular scale and its main scale is graduated in such a way that each centimeter is divided into 20 divisions. Calculate

(a) Pitch (b) Least count (c) the diameter of a wire measured using it (Refer to the figure below).

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