Comprehensive PRACTICAL PHYSICS FOR CLASS XI Strictly according to new curriculum prescribed by Central Board of Secondary Education (CBSE) and State Boards of Chhattisgarh, Haryana, Bihar, Jharkhand, Kerala, Mizoram, Meghalaya, Uttarakhand and other states following NCERT curriculum By J.N. Jaiswal Formerly, Head of Deptt. of Physics Hindu College, Sonepat Haryana Dr. Rajendra Singh M.Sc., B.Ed., Ph.D., Delhi University J.D. Tytler School New Rajinder Nagar Delhi LAXMI PUBLICATIONS (P) LTD BANGALORE CHENNAI COCHIN GUWAHATI HYDERABAD JALANDHAR KOLKATA LUCKNOW MUMBAI RANCHI NEW DELHI BOSTON, USA
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Contents Pages Syllabus... (x) (xii) Chapter 1. General Introduction... 1 22 SECTION A Chapter 2. Measurement of Length... 23 57 Exp. 1. To measure diameter of a small spherical/cylindrical body, using vernier callipers.... 30 Exp. 2. To measure internal diameter and depth of a given beaker/ calorimeter using a vernier callipers and hence find its volume.... 36 Viva voce... 39 Exp. 3. To measure diameter of a given wire using a screw gauge.... 45 Exp. 4. To measure thickness of a given sheet using a screw gauge.... 48 Exp. 5. To determine volume of an irregular lamina using a screw gauge.... 50 Viva voce... 51 Exp. 6. To determine radius of curvature of a given spherical surface by a spherometer.... 54 Viva voce... 57 Chapter 3. Measurement of Mass... 58 75 Exp. 7. To determine the mass of two different objects using a beam balance.... 71 Viva voce... 73 Chapter 4. Measurement of Time... 76 81 Viva voce... 81 Chapter 5. Vector Addition... 82 90 Exp. 8. To find the weight of a given body using parallelogram law of vectors.... 85 Viva voce... 89 Chapter 6. Motion Under Gravity and Acceleration due to Gravity... 91 101 Exp. 9. Using a simple pendulum, plot l-t and l-t 2 graphs. Hence find the effective length of a second s pendulum using appropriate graph.... 91 Viva voce... 101 Chapter 7. Friction... 102 110 Exp. 10. To study the relationship between force of limiting friction and normal reaction and to find the coefficient of friction between a block and a horizontal surface.... 107 Viva voce... 110 (v)
(vi) Chapter 8. Motion of a Body Down an Inclined Plane... 111 116 Exp. 11. To find the downward force along an inclined plane acting on a roller due to gravitational pull of the earth and study its relationship with the angle of inclination by plotting graph between force and sin θ.... 113 Viva voce... 116 Activities A.... 117 134 Act. 1. To make a paper scale of given least count e.g., 0.2 cm, 0.5 cm.... 117 Act. 2. To determine the mass of a given body using a metre scale by principle of moments.... 119 Act. 3. To plot a graph for a given set of data, with proper choice of scales and errors bars.... 122 Act. 4. To measure the force of limiting friction for rolling of rollers on a horizontal plane.... 124 Act. 5. To study the variation in the range of a projectile with the angle of projection.... 126 Act. 6. To study the conservation of energy of a ball rolling down on an inclined plane, (using a double inclined plane).... 128 Act. 7. To study dissipation of energy of a simple pendulum, by plotting a graph between square of amplitude and time.... 130 Viva voce... 134 SECTION B Chapter 9. Elasticity... 135 153 Exp. 1. To determine Young s Modulus of elasticity of the material of a given wire.... 141 Exp. 2. To find the force constant of a helical spring by plotting graph between load and extension.... 147 Viva voce... 150 Chapter 10. Atmospheric Pressure... 154 161 Exp. 3. To study the variation in volume with pressure for a sample of an air at constant temperature by plotting graphs between P and V and between P and 1/V.... 157 Viva voce... 161 Chapter 11. Surface Tension... 162 172 Exp. 4. To determine the surface tension of water by capillary rise method.... 167 Viva voce... 171 Chapter 12. Viscosity... 173 178 Exp. 5. To determine the coefficient of viscosity of a given viscous liquid by measuring terminal velocity of a given spherical body.... 176 Viva voce... 178
(vii) Chapter 13. Thermal Expansion of Solids... 179 182 Viva voce... 182 Chapter 14. Thermal Expansion of Liquids... 183 184 Viva voce... 184 Chapter 15. Thermal Radiation... 185 190 Exp. 6. To study the relationship between the temperature of a body and time by plotting a cooling curve.... 187 Chapter 16. Wave Motion and Velocity of Waves... 191 198 Viva voce... 196 Chapter 17. Vibration of Strings and Air Columns... 199 226 Exp. 7. To determine specific heat of a given (i) solid, (ii) liquid, by the method of mixtures.... 206 Exp. 8. (i) To study the relation between frequency and length of a given wire under constant tension using sonometer. (ii) To study the relation between the length of a given wire and tension for constant frequency using sonometer.... 209 Viva voce... 215 Exp. 9. To find the speed of sound in air at room temperature using a resonance tube by two resonance positions.... 222 Viva voce... 225 Chapter 18. Heat... 227 229 Viva voce... 229 Activities B.... 230 246 Act. 1. To observe change of state and plot a cooling curve for molten wax.... 230 Act. 2. To observe and explain the effect of heating on a bimetallic strip.... 232 Act. 3. To note the change in level of liquid in a container on heating and interpret the observations.... 235 Act. 4. To study the effect of detergent on surface tension by observing capillary rise.... 237 Act. 5. To study the factors affecting the rate of loss of heat of a liquid.... 238 Act. 6. To study the effect of load on depression of a suitably clamped meter scale loaded at (i) its end (ii) in the middle.... 241 Act. 7. To observe the decrease in pressure with increase in velocity of a fluid.... 244 DEMONSTRATION EXPERIMENTS... 247 287 Demo. 1. To demonstrate that a centripetal force is necessary for moving a body with a uniform speed along a circle, and that the magnitude of this force increases with increase in angular speed.... 247 Viva voce... 248
(viii) Demo. 2. To demonstrate inter conversion of potential and kinetic energy.... 249 Viva voce... 251 Demo. 3. To demonstrate conservation of linear momentum.... 251 Viva voce... 253 Demo. 4. To demonstrate conservation of angular momentum.... 253 Demo. 5. To demonstrate the effect of angle of launch on the range of a projectile.... 254 Viva voce... 257 Demo. 6. To demonstrate that the moment of inertia of a rod changes with the change of position of a pair of equal weights attached to the rod.... 258 Viva voce... 260 Demo. 7. To study variation of volume of a gas with its pressure at constant temperature using a doctor s syringe.... 261 Viva voce... 262 Demo. 8. To demonstrate Bernoulli s theorem with simple illustrations.... 263 Viva voce... 265 Demo. 9. To demonstrate that heat capacities of equal masses of different materials are different.... 266 Viva voce... 268 Demo. 10. To demonstrate free oscillations of different vibrating system.... 268 Viva voce... 271 Demo. 11. To demonstrate resonance with a set of coupled pendulum.... 272 Demo. 12. To demonstrate longitudinal and transverse waves.... 274 Viva voce... 276 Demo. 13. To demonstrate the phenomenon of beats, due to superposition, of waves produced by two sources of sound of slightly different frequencies.... 276 Viva voce... 278 Demo. 14. To demonstrate resonance using an open pipe.... 279 Viva voce... 281 Demo. 15. To demonstrate the direction of torque.... 282 Viva voce... 283 Demo. 16. To demonstrate the law of moments.... 284 Viva voce... 285 Appendix... 288 290 Logarithmic and Other Tables... (i) (xviii)
Preface to the New Edition This new edition of Comprehensive Practical Physics Class XI is according to the latest syllabus as suggested by NCERT and adopted by CBSE. It is complete in all respects to meet the requirement of our talented teachers, colleagues and illustrious students. They will like it in same manner as they liked the earlier editions. The bringing out of an early revised edition indicates that the book has found its place amongst the learned and the learners. For this we are highly thankful to all of them. This has given us an encouragement to serve the teaching and the learning cause in a better way. The salient features of the book are : 1. Experiments have been classified into chapters, and chapters arranged in same order as in a theory book. 2. In each chapter, complete theory has been given for all topics, even if there is no experiment based on them. This has been done to maintain continuity. 3. Experiments have been described systematically covering all parts, especially the procedure has been given step-wise. 4. At the end of each experiment or group of similar experiments, a sufficient number of oral questions with answers have been given for viva-voce. This single book is three-in-one serving as a theory, a practical and an oral questionanswer book. AUTHORS (ix)
Syllabus CLASS XI (PRACTICALS) (Total Marks : 30) The record, to be submitted by the students, at the time of their annual examination, has to include Record of at least 15 Experiments [with a minimum of 8 from section A and 7 from section B], to be performed by the students. Record of at least 5 Activities [with a minimum of 2 each from section A and section B], to be performed by the students. Report of at least two demonstration experiments, to be carried out by the teacher. Evaluation Scheme Two experiments one from each section Practical record (experiment & activities) Record of Demonstration experiments Viva on experiments & activities 8 + 8 Marks 6 Marks 2 Marks 6 Marks 30 Marks SECTION A Experiments (Any 8 experiments out of the following to be performed by the Students) 1. To measure diameter of a small spherical/cylindrical body using Vernier Callipers. 2. To measure internal diameter and depth of a given beaker/calorimeter using Vernier Callipers and hence find its volume. 3. To measure diameter of a given wire using screw gauge. 4. To measure thickness of a given sheet using screw gauge. 5. To determine volume of an irregular lamina using screw gauge. 6. To determine radius of curvature of a given spherical surface by a spherometer. 7. To determine the mass of two different objects using a beam balance. 8. To find the weight of a given body using parallelogram law of vectors. 9. Using a simple pendulum, plot L-T and L-T 2 graphs. Hence find the effective length of a second s pendulum using appropriate graph. 10. To study the relationship between force of limiting friction and normal reaction and to find the co-efficient of friction between a block and a horizontal surface. (x)
11. To find the downward force, along an inclined plane, acting on a roller due to gravitational pull of the earth and study its relationship with the angle of inclination (θ) by plotting graph between force and sin θ. Activities (xi) 1. To make a paper scale of given least count, e.g., 0.2 cm, 0.5 cm. 2. To determine mass of a given body using a metre scale by principle of moments. 3. To plot a graph for a given set of data, with proper choice of scales and error bars. 4. To measure the force of limiting friction for rolling of a roller on a horizontal plane. 5. To study the variation in range of a projectile with angle of projection. 6. To study the conservation of energy of a ball rolling down on an inclined plane (using a double inclined plane). 7. To study dissipation of energy of a simple pendulum by plotting a graph between square of amplitude and time. SECTION B Experiments (Any 7 experiments out of the following to be performed by the Students) 1. To determine Young s modulus of elasticity of the material of a given wire. 2. To find the force constant of a helical spring by plotting graph between load and extension. 3. To study the variation in volume with pressure for a sample of air at constant temperature by plotting graphs between P and V, and between P and 1/V. 4. To determine the surface tension of water by capillary rise method. 5. To determine the co-efficient of viscosity of a given viscous liquid by measuring the terminal velocity of a given spherical body. 6. To study the relationship between the temperature of a hot body and time by plotting a cooling curve. 7. To determine specific heat of a given (i) solid (ii) liquid, by method of mixtures. 8. (i) To study the relation between frequency and length of a given wire under constant tension using sonometer. (ii) To study the relation between the length of a given wire and tension for constant frequency using sonometer. 9. To find the speed of sound in air at room temperature using a resonance tube by two-resonance positions. Activities 1. To observe change of state and plot a cooling curve for molten wax. 2. To observe and explain the effect of heating on a bi-metallic strip. 3. To note the change in level of liquid in a container on heating and interpret the observations. 4. To study the effect of detergent on surface tension by observing capillary rise.
(xii) 5. To study the factors affecting the rate of loss of heat of a liquid. 6. To study the effect of load on depression of a suitably clamped metre scale loaded at (i) its end (ii) in the middle. 7. To observe the decrease in pressure with increase in velocity of a fluid. DEMONSTRATION EXPERIMENTS 1. To demonstrate that a centripetal force is necessary for moving a body with a uniform speed along a circle, and that the magnitude of this force increases with increase in angular speed. 2. To demonstrate inter-conversion of potential and kinetic energy. 3. To demonstrate conservation of linear momentum. 4. To demonstrate conservation of angular momentum. 5. To demonstrate the effect of angle of launch on range of a projectile. 6. To demonstrate that the moment of inertia of a rod changes with the change of position of a pair of equal weights attached to the rod. 7. To study variation of volume of a gas with its pressure at constant temperature using a doctors syringe. 8. To demonstrate Bernoulli s theorem with simple illustrations. 9. To demonstrate that heat capacities of equal masses of different materials are different. 10. To demonstrate free oscillations of different vibrating systems. 11. To demonstrate resonance with a set of coupled pendulums. 12. To demonstrate longitudinal and transverse waves. 13. To demonstrate the phenomenon of beats, due to superposition of waves produced by two sources of sound of slightly different frequencies. 14. To demonstrate resonance using an open pipe. 15. To demonstrate the direction of torque. 16. To demonstrate the law of moments.
1 General Introduction 1.01. SCIENCE AND PHYSICS The word science originates from the Latin word Scientia meaning to know. Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible and use the knowledge so gained to predict, modify and control the phenomena. Science is exploring, experimenting and predicting from what we see around us. The science unravels the secrets of nature. Physics is a basic discipline of Natural Sciences. The word Physics comes from a Greek word fusis which means nature. Its Sanskriti equivalent is Bhautiki which means study of physical world. Physics is the study of the basic laws of nature and their manifestation in different natural phenomena. It deals with the study of nature and natural phenomena, involving matter and energy, and their interconversion. 1.02. PHYSICAL QUANTITIES AND MEASUREMENTS All quantities in terms of which laws of physics can be expressed and can be measured directly or indirectly accurately are called physical quantities. The process adopted for knowing the magnitude of a physical quantity, is called measurement. It is done by comparing the physical quantity with a standard of same nature. Measurement required a reference standard which is arbitrarily chosen, internationally accepted is called unit. The result of a measurement of a physical quantity is expressed by a number accompanied by a unit. Measurement is an important part in the study of physics. Physics is an exact science. 1.03. IMPORTANCE OF LABORATORY IN SCIENCE Science, like religion, is a search for truth. A laboratory is a place of worship, where this search is carried on. Hence to a scientist, his laboratory should be as sacred and pious as the place of worship to a devotee. In fact, laboratory is such a place of worship, where young 1
2 COMPREHENSIVE PRACTICAL PHYSICS XI scholars should equip themselves for something higher and nobler a search for truth and unravelling the mystries of nature. 1.04. AIM OF THE EXPERIMENTAL STUDY From a careful study of history of progress of science, we conclude that an experiment is the basic foundation for the development and growth of science. The main aim of experimentation in science is to verify a given law which has already been derived from a theory. While doing an experiment with open eyes and attentive mind, new discoveries have been made during experimentation. Physics is an experimental science. A clear understanding of its principles can be made by demonstrating the experiments by one s own hands. 1.05. SCIENTIFIC METHOD A method involving systematic study of a phenomenon or systematic performance of a process, is called a scientific method. It involves following steps in the order given below : (i) Object. To fix the phenomenon to be studied. (ii) Apparatus. To collect the equipment (instruments) required during the study. (iii) Experimentation. To measure the quantities involving in the phenomenon with the help of acquired instruments. (iv) Observation. To record the numerous data (measured quantities) in a tabular form. (v) Hypothesis. To analyse the data and find how that affects the phenomenon. Also to establish relationship between different quantities of a data, graphically or otherwise. (vi) Verification. It is done by applying the hypothesis to other similar phenomena. (vii) Predictions. To name new phenomena by changing the variables (quantities) involved in the study of main phenomena. (viii) New experiments. These are done to check the existence of predictions. (ix) Modifications. With the passage of time more refined instruments become available. Their use needs modification of old methods and procedures of experimentation. The above cycle is repeated. Thus, experimentation is an unending process which is quite vital for the development of any kind of science. Physics is no exception. 1.06. GENERAL INSTRUCTIONS FOR AN EXPERIMENTALIST 1. Come prepared from home with the experiment you are going to perform. Read directions very closely, as in every word there is a significance without having a clear
GENERAL INTRODUCTION 3 idea of what is to be done and how/why is to be done. Doubts, if any, should be got removed from the teacher before starting the experiment actually. 2. Collect the necessary apparatus by request and to avoid unnecessary waste of time, the students should carefully check up each item of the working apparatus. If you do not understand the principle, construction and the use of the measuring instruments you are to use, do not hesitate to consult your teacher. It is particularly important for electrical instruments, where a slight negligence on the part of the student may damage a costly apparatus. 3. Handle the apparatus very carefully, specially the small weights, nuts, screws and glass apparatus. In the event of a loss or breakage, report the matter immediately to the person concerned (Lab. Incharge). Do no wait to be detected. 4. Keep your table neat and clean and free from all unnecessary articles, such as hats, books, umbrellas, etc. Place them at some convenient place in the laboratory. Do not disfigure the table with chalk, pencil, ink or finger-nail marks. 5. Precautions given for the experiments must be actually observed while doing the experiment. 6. Do not allow water, alcohol, mercury or other chemicals to come in contact with the metallic parts of the apparatus. Apparatus so spoiled should be wiped clean with a wet cloth, dried and smeared with vaseline. Do not disfigure the wooden parts of the apparatus. 7. While setting the apparatus, take care to see that the apparatus which requires frequent manipulation or reading is within easy reach. The apparatus should be arranged in an orderly manner. 8. Observe twice or more the reading correctly, and write on the observation copy and get checked and signed by teacher incharge. Make correct calculation for required result and then, recorded on the fair note-book. When recording an observation, do not forget to note down the units in which the measurement is made. Each quantity measured should be recorded in decimals and not in fractions. The result too should be given in proper units except when the quantity is pure ratio, e.g., specific heat, specific gravity, etc. 9. Always take a series of observations and as far as possible record them in a tabular form. At least one reading must be checked and verified by the teacher incharge while doing the experiments. An isolated reading is meaningless except in weighing, in taking temperatures or in measuring big lengths. 10. Long and tedious calculations should be done by logarithms ; this saves time as well as reduces the chances of error. 11. Do your work honestly and never cook the result by recording false observations or by making wrong calculations to show a correct result. The students should remember that the purpose of each experiment is to unmask the truth, hence nothing but truth should be recorded. 12. Before leaving the laboratory : (i) The student should get his note-book signed. (ii) All the apparatus should be returned to the laboratory assistant. No apparatus should be left on the table. (iii) The student should get an experiment assigned for the next turn.
4 COMPREHENSIVE PRACTICAL PHYSICS XI 1.07. RECORDING OF EXPERIMENT IN THE PRACTICAL FILE The practical file for physics is a well-stitched note-book having left-hand page blank and right-hand page ruled. It has pages of useful formulae in the beginning and many cm graph pages at the end. A neat and systematic recording of the experiment in the practical file is very important for achieving complete success in the experimental investigations. A student may write the experiment under the following headings in his main practical note-book. There may be slight variations in suggestions from the teacher. In that case, teacher s instructions must be followed. On the Left Hand Page (Blank Page) 1. Diagram. The diagram shows the sketch of the apparatus used. Different important parts must be well-labelled. Sometimes more than one diagram may be required to explain different stages of the experiment. A circuit diagram in an electricity experiment and a ray diagram for optical (light) experiment is must. 2. Calculations. Formula used is written and observed values are substituted. Simplification is performed. Use log tables for multiplications and divisions and show steps of these calculations neatly in the note-book. (Do not treat log calculation as a rough work.) 3. Verification. The result is obtained by some other direct method and results are compared. 4. Percentage error. In case the quantity determined has some standard value, percentage error is calculated by the following formula : Percentage error = Actual value ~ Observed value Actual value 100. On the Right Hand Page (Ruled Page) Date... Experiment No... Page No... 1. Object. The object of the experiment to be performed should be stated clearly and precisely. 2. Apparatus. Instruments and items required for performing the experiment, are listed here. 3. Theory. In this head, the statement of the law to be verified or the principle involved in the experiment must be written. The formula used must also be written clearly explaining the symbols involved. The derivation of formula is not necessary. 4. Procedure. The different steps taken for performing the experiment must be mentioned in short. The description must be in first person and past tense (e.g., I did this. I did that). 5. Observations. First, least count of the measuring instrument must be derived and written in detail. Single observations are recorded in one or two lines. Two or more observations must be recorded in tabular form. Observations taken in single step must have three sets with changed values. For drawing a graph, six set of observations must be taken. 6. Result. Express the result with proper unit and sign.