Practical Physics for Degree Students - Gias Uddin and Shahabuddin PDF

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r-! I PRACTICAL PITTSICS for degree students (8. Sc. Pass, Honours and Engineering Students) Dr. Giasuddin Ahmad. B. Sc. Hons. M. Sc. (Dhaka), Ph. D. (Glasgow) Professor, Department of Physics Bangladesh University of Engineering and Technology, Dhaka. and Md. Shahabuddin, M. Sc. M. A- Librarian, B...

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r-! I

PRACTICAL PITTSICS for degree students

(8. Sc. Pass, Honours and Engineering Students) Dr. Giasuddin Ahmad. B. Sc. Hons. M. Sc. (Dhaka), Ph. D. (Glasgow) Professor, Department of Physics Bangladesh University of Engineering and Technology, Dhaka.

and

Md. Shahabuddin, M. Sc. M. ALibrarian, Bangladesh University of Engineering and Technologr, Dhaka. Formerly of the Department of Physics. Ahsanullah Engineering College and Bangladesh University of Engineering and Technology, Dhaka.

FOURTH EDITION ThoroughLg reuised bg ProJ. Giasuddin Ahmad Ph. D. Department of PhUsics, Bangtadesh Uniuersitg oJ Engineering and" Technologg. Dhcrka

IrIAF.IZ BOOK CENTRE

CIIAPTER I. INTRODUCTION

PREFACE TO FIRST EDITION The "Practic-al Physis5 for Degree Students" is designed to co\rer the syllabi of the B.Sc. Pass and Subsidiary and B. Scl@ngineering) examinations of the different Unlrrersities of pakistan. our long experience in teaching physics and conducting practical classes has acquainted us with the various difficulties=that the students face in performing experiments. In this textbook attempts have been made to guide the students so that they may proceed to record data systematically and then correlate them to get the results. strbject mafter of the book has been presented in i'simple manner so that the students may independently perform the experiments without the help of the teachers. At the end of each experiment relevent questions and their answers harre been provided, thus clarilying the theoretical aspect of the experiment. lables are provided at the end of each eiperiment. Hor,vever, it should be remembered that they are purely suggestive and there is nothing special about any particular form of tl-bulation. Tables of physical constants and logarithmic and trigonometrical tables have been provided at the end of the book for ready reference. In writlng this book we consulted different books on practical physics specially those by Watson. Worsnop and Flint, Allen and Moore, S Datta, K. G. Majumdar, Roy Choudhury, Ganguli, H. Singh, J Chatterjee and K. Din. Various theoretical books hive also been

ArL

1.1

Art. Art.

1.2 1.3

Importance of laboratory work Errors in measurements Degree of accuracy in measurement

Art. Art. Art.

1.4 1.5 1.6

Drawing of graphs Experimental guidelines A few general instructions

We like to thank Professor K. M. Saha, M.Sc. Head of the Department of Physics, E. P. University of Engineering and Techonlogr, Dacca, for hts keen interest in the 6ook an? his constant encouragefirent and guidance. We also like to thank our

Art.

consulted.

colleagues Mr. T. Hossain. M. Si. and Mr. Asadullah Khan. M. Sc. for

their various helps rendered during the preparation of this book. We gratefully acknowledge the debt we owe to Mr. Nurul Momen. M. Sc. (Dac), M. A. (Columbia) for many valuable and constructive suggestions.

We also like to thank Mr. Hassan Zoberi of M/S. Zoberi and pearl

for his active co-operation in bringing out this book. Thanks are also due to Mr. Anwar Ali of the Department of physics rvho helped us in getting the manuscript typed within a short time. The book has been hurried through the press and as such some printing mistakes might have crept in inspite of our best efforts. We shall -gratefully welcome any suggestion which may help to improve the book.

callipers

2.1

The slide

Expt.

l.

To measure the length of a rod with a

ArL

2.2

Expt.

2.

AIL Expt.

2.3

Art-

The balance Travellins microscoDe

Art"

2.4 2.5 2.6

Expt.

4.

To weigh a body by the method of

Expt.

5.

Expt.

6.

Expt.

7.

Expt.

8.

To draw a graph showing the sensitivity of a balance with loads To determine the Young's modulus for the material of a wire by Searle's apparatus To determine the Young's modulus by the flexure of a beam (bending method) To determine Young's modulus (Y), rigidity modulus (n) and Poisson's ratio (o) of a short wire by Searle's dynamic

vernier callipers. The screw gauge To measure the diameter of a piece of wire with a screw gauge and to find its average cross-section

J.

The spherometer To determine the thickness of a glass plate wlth a spherometer Cathetometer

oscillation

method

Expt.

9.

I 4 5

I

t2

II. GENERAL PROPERTIES OF MATTPR

Art.

to.

E. P. University of Engineering and Technologr. Dhaka.

To determine the modulus of rigidity of a wire b1r statical method. To determine the modulus of rigidity of a

13

l5 18

20 23 24 30 32 34 37 39 43 50

55 59

wire by the method of oscillations

IstJanuary, 1969

Giasuddin Ahmad Md. Shahabuddin

\

CHAPTER

I

a/@yfintic method) Expt. l\lt\. ,/ T{debrmine the spring constant and '.-.{v /effective mass of a given spiral spring and

65

l-he material of the spring

68

hence to calculate the rigidity modulus of

Expt.

t4.

Expt.

15.

Expt.

16.

Expt.

17.

Expt.

t8.

To determlne the moment of lnertia of a fly-wheel about its axis of rotation. To determine the value of g, acceleration due to gravity, by means of a compound pendulum To determlne the value of 'g, by Kater's reversible pendulum. To determine the surface tension of water by capillary tube method and hence to veriff Jurin's law. To determine the surface tension of mercury and the angle of contact by Quincke s method. To determine the surface tension of a liquid by the method of ripples (Rayleigh's method) To determine the co-efficient of viscosity of a liqutd by its flow ilrrough a capillary tube.

Expt. Expt.

tle

19.

To show

20.

with temperature. To verift Stoke's law and hence to

variation of viscosity of water

determine the viscosity of a liquid (glycerine)

CIIAPTER Expt.

21.

Expt.

22.

Expt.

23-

Expt.

24.

Expt.

25.

Expt.

26.

Expt.

27.

28.

Expt.

29.

To determlne the co-efficient of thermal conductivtty of a metal using Searle's

Expt.

30.

Expt.

31.

To determine the thermal conductivitv of a bad conductor by Lees and Chorlton's method To determine the ratio of speciflc heats at constant pressure and constant volume (Y = co/cr.) for air by Clement and

Expt.

32.

apparatus

7A

84 89 95 99

CHAPTER

ArL

4.1.

105 4.2.

ArL Expt.

4.3.

Expt.

34.

120

Expt.

35.

r28

Expt.

36.

134

Expt.

37.

33.

tt4

To determine the pressure co-efficient of a g.as at constant volume by constant volume air thermometer To determine the co-efficient of expansion ofair at constant pressure by constant pressure air thermometer To determine the true temperature of a mixture by radiation correction To determine the specific heat of a solid by the method of mixture with radiaUon To determine the specific heat of a liquid by the method o[ mixture To determine the specific heat of a liquid by the method of cooling To determine the latent heat of fusion of ice by applying the method of radiation

correction To determine the latent heat of steam by applying the method of radtailon correction

140

152 157

IV -

Interference of sound and stationary

waves

Vibration of a string fixed at both ends To find the variatlon of the frequency of a tuning fork with the length of a sonometer (n-l curve) under given tension and hence to determine the unknown frequency of a tuning fork To veriff the laws of transverse vibratlon of a stretched string by sonometer To veriff the laws of transverse vibration of strings and to determlne the frequency of a tuning fork by Melde's experimlnt To determine the velocity of sound in air by Kundt's tube To determine the ratlo of the specific heat at constant pressure of air to that at constant volume 1y= CO/C) by Kundt's

Expt.

5.1

,:7

l g4 l g4

186

I92 i96 2Ag

V - LIGHT

Parallax The optical bench and its uses.

kns

To determine the focal length and hence the power of a convex lens by displacement method wlth the help of an

optical

l8t

208

CIIAPTER 5.2 5.3

172

SOUND

tube.

Art. Art. Art.

t67

Some terms connected with experlments

144 146

t62

177

on sound

tuL llo

Desorme's method. To determine the density of water at various temperature by means of a glass

sinker

III . HEAT

correction

Expt.

73

bench

2to 2r2 2t4

221

Expt.

determine the focal length and hence - vz/)" the power of a concan e lens by using an ^W arxiliary convex lens .10. ,rTo delermine the refractirre index of a fvf-/ liquid by pin method trsing a plane mirror

CHAPTER

I

Ex1.lt.

Expt. 4l Expt. Art. Expt. Expt.

.dpt. Art Expt.

42

5.4

43.

44. 4s. 5.5 46.

u*^/ Art. Expt. Art. Expt.

5.6

44.

5.7

49.

and a convex lens To determine the refractive index of the material oF a convex lens by a telescope arrd splrerometer To determine by Boy's method a. the radius of curvature of a lens and b. the refractir,e index of the material of

237

7.4 7.5 7.6 7.7 7.8

Art.

7.9

7.1

7.2 7.3

241

245

E-xpt.

53.

rays

255

Expt. Expt.

54. 55.

grq{-

sa

Art.

7.1O

To determine the angle of a prism (by

rotation of the telescope) To determine the refractive index of the material of a prism lnterference of light To determine the radius of curvature of a lens by Newton's rings To determine the wavelength of nronochromatic light by Newton's rings Essential discussions for diffraction experiments To determine the wavelengths of various spectral lines by a spectrometer using a plane diffraction grating Polarization of light To calibrate a polarimeter and hence to determine the specific rotation of a sugar solution by means of a polarimeter

VI .

260 264 270 274

284 285

29r 294 306

Expt. ..57 ,/

--gx{t. Expt. Expt.

E8 59. 60.

Expt. 6l

MAGNETISM

Expt.

51.

Magnetometers To deterrnine the horizontal component of the earth's magnetic field and the magnetic moment of a magnet by enrploying magnetometers To compare the n-ragnetic moments of two

Expt.

52.

nlagnets To measure the magnetic dip at a place.

6.1 50.

232

Art. Art. Art. Art. ArL Art. Afl. Art.

the lens Experiments rr,,ith the spectrometer 'l-o foctts the spectrometer for parallel

CIIAPTER

tut. Expt.

227

314

317 324

Expt.

62

VII .

ELPCTRICITY

Sonre electrical accessories Electrical cells and their uses Galvanometers and their uses Shunts

Ammeters

Voltmeter Polarity tests General rules to be observed in electrical experiments Principle of Wheatstone's network: metre bridge; post office box To determine the end-corrections o[ a metre bridge To calibrate a metre bridge wire To determine the specific resistance of a wire using a metre bridge To determine the value of unknown resistence and to verify the laws of series and parallel resistances by means of a Post Office Box Uses of suspended coil type galiranometer

7.12.

Expt.

63.

7

.l I

JZi)

Expt. -9d

354 355 359 364 367

371 378

To determine the figure of merit of a galvanometer

379

To deterrnine the resistance of a galvanometer by half-deflection method. To determine a high resistance by the

gB2

method of

385

deflection

To determine the value of low resistance by the method of fall of potential (Mathiesen and Hopkin's method of

projection)

To determine the electro-chemical eqrrivalent of copper by using an ammeter and copper voltameter Determination of electro-chemical equivalent of silver using an ampere balance

Art. Art.

330 340 346 349 350 352 353

Potentiometer and its action Precautions to be taken in performing experiments with a potentiometer To determine the'e.m.f. of a cell rvith a potentiometer of known resistance using a milliammeter To compare the e.m.f. of two cells with a

potentiometer

389

394 396 403

406 408

4lO

/

Expt.

65.

To measure the current flowlng through a resistance, by measuring the drop of potential across it, wlth the help of a

K(

66

Expt.

67

To determlne the internal resistance of a cell by a potentiometer To calibrate an ammeter by potential drop

Expt.

68

To calibrate a voltmeter by a

Expt. Expt. ArL Expt. Expt.

potentiometer

method with the help of a potentiometer

69

7O

7.13

Carey Foster's bridge

71

To determine the resistance per unit length of metre bridge wire To compare two nearly equal low resistances by Carey Foster's bridge To determine the temperature coefficient of the reslstance of the material of a wire To determine boiling point of a liquid by platlnum reslstance thermometer To construct an one ohm coil Thermo-couple To plot the thermo-electromotive forcetemperature (calibration curve) for a given thermo-couple and hence to determtie

72

Expt. J3-' l

Expt. Expt. Art. Expt. Expt.

potentiometer To determine the value of J, the mechanical equivalent of heat, by electrical method To determine the value of J, the mechanical equlvalent of heat by Callendar and Barnes electrical method

7

4

75 7.14

76

77

Art. Expt.

7.15

Art. Expt.

7.16

7a.

its thermo-electric

power

To determine the melting point of a solid by means of a thermo-coupte with the help of a calibration curye. The triode val.se-tts descrtption and action To draw the characteristic curves of a triode and hence to determtne its constants

79

Expt. 80 Art. 7.17 Expt. 8l

Semiconductor diode To drarv the characteristics of a pn junction (semi conductor) diode. To determine e/m of electron using Helmholtz coil Photo-electric effect To determine the threshold frequency for photo-electric effect of a photo-iathode and the value of the Planck's constant by using a photo-electric cell

CONTENTS OF ADVANCED PRACTICAL PHYSICS

417

421

*

* 424 429

{.

* *

+JJ

454 464 467

To determine the refractive index of the material prism by the method of normal incidence.

of the thin

spectrometer.

To measure the dispersive power of the material of a prism by

443

450

To determine the angle of prism by rotation of the prism table. To determine the refractive index of the material of a prism.

To determine the refractive index of the material of a prism and a given liquid by total internal reflection using a

439 443

447

To determine the thermal conductivity of rubber. To determine Stefan's constant.

* *

spectrometer using a discharge tube. To calibrate a spectrometer.

To determine the Cauchy's constants and the resolving power of the prism using a spectrometer.

To determine the wavelength of monochromatic light

by

Fresnel's bi-prism.

To determine the thickness (or refractive index) of a very thin transparent plate.

To determine the refractive index of a liquid (available in 470 481

447

minute quantities) by Newton's rings.

To determine the

separation between D1 and D2 lines of

sodium by Michelson interferometer.

To determine refractive index (or thickness) of a film by Michelson intOrferometer.

To

determine wavelength

of

monochromatic

light

by

489 499

Michelson interferometer.

505

To determine the melting point of a solid by means of

511

516

To

determine the logarithmic decrement of a ballistic to determine its critical damping

galvanometer and hence resistance.

519

a

thermo-couple with the help of a calibration curve.

CIIAPTER T INTRODUCTION r.T IMPORTANCE OT LIIBORATORY WORK A student of physics should realise that the laboratory work, popularly known as practical classes, is no less important than the theoretical lectures. In performing an experiment in the laboratory, one is required to revise thororrghly t.he ideas and the principles involved in the experin)ent which were explained by the teachers in the t.heoretical classes, possibly long ago. Thus practical classes serve as a sor[ of revision exercises of the theoretical lectures. Moreorrer, laboratory work n-lakes a student methodical, accurate, diligent and trained to rules of discipline. The overall aims of the physics practical programme are to help the students learn a to experiment i.e. measure unknown quantities and draw conclusion from them. b. to write scientific (or technical) reports and papers and c. to use specialized methods of experimental measu_ rement.

r.2 ERRORS IN MEASUREMENTS In detemining a physical consta,t in Lhe raboratory, it is

...