PHYSICS LABORATORY MANUAL

1 PHYSICSLABORATORYMANUALFor Undergraduates2013-14 The LNM Institute of Information TechnologyRupa ki Nangal, Post-Sumel, Via-Jamdoli,Jaipur - 302031, Rajasthan, IndiaLaboratory Regulations1. You should arrive Mobiles must be switched Experiments will be performed in pairs. Stay with the same person throughout thesemester, otherwise problem will arise in allocating you Attendance is compulsory. Absence for some reasons should be notified in advanceto the You are required to record your observations in a hardback LABORATORY student will maintain his/her LABORATORY notebook.

2 You must get at least oneobservation of each kind checked and signed by your You must complete all experimental work during the three hours session. Everyobservation made must be recorded directly on the LABORATORY notebook. No roughrecord is You are required to submit the complete report in your next LABORATORY Measurement & Instruments4B. Error bars on graphs12C. A comment of significant digits131. Introduction to Error Analysis and Graph Mass Spring System .. Resistivity of a of nichrome wire.

3 Finding and initial voltage across capacitor .. Resonant Rings .. To measure the electrical resistance of a given material .. 182. Gyroscope and Moment of Inertia of a Wheel203. Damped and Forced Oscillators: Bar Pendulum and LCR Circuit294. Fraunhoffer Diffraction405. Refractive index of glass with the help of a prism446. Helmholtz coil and eddy currents527. Mechanical waves and Climate simulation578. Electromagnetic induction and Van de Graff generator639. Hall Effect7110. Diffraction grating7711.

4 Measurement of band gap of semiconductor833A. Measurement & InstrumentsThis section of the MANUAL describes the basic measurements and allied instruments thatyou will encounter in the MeasurementsIn the grouping of physical measurements the quantities to be measured are length, mass,angle and are three basic instruments for the measurement of length, (i) the meter ruler, (ii)the micrometer screw gauge and (iii) the vernier calipers. The table below details therange and accuracy of these three Ruler0 100cm1mmMicrometer Screw Gauge0 Calipers0 , there is a wide variation in the range of the instruments and the first lesson isthat the choice of instrument is determined by the length that is to be measured.

5 If thelength is 50cm, then it clearly should be the Metre Ruler. The second lesson concerns theaccuracy. In principle, you can measure a length of 2cmwith all three instruments butthe accuracy of your measurement will vary from 1mmto The choice, then, isalso determined by the accuracy required. The accuracy of an instrument depends on itsconstruction & operation and this is now described for each instrumentMeter ruler:The principle of the metre ruler is very simple. A known length (1 metre)is divided into 100 unit lengths of 1cm.

6 And these are further subdivided into 10 unitlengths of 1mm. The accuracy of the instrument is the smallest division, namely : Place one end of the ruler (or an appropriate zero ) at one end of thelength to be measured and read off the nearest value at the other end of the length to screw gauge:The principle of the micrometer is the screw thread. Thepitch of the screw is that is one complete rotation of the screw advances or retractsthe screw by Underneath the rotating barrel of the gauge is a ruler with (actually two sets of 1mmdivisions offset by ).

7 The rotating barrel isitself subdivided into 50 units, such that rotation of the barrel through one unit advancesor retracts the screw by = ; the accuracy of the instrument is : Place the object between the fixed and moving end faces and rotate thebarrel until the object is in contact with both end rotate using the smallslip knob at the end of the will ensure contact without damage to theobject or the micrometer. The measured length is the reading on the ruler to the nearestfull portion of this unit shown on the rotating checkthe visible zero setting and all for any offset from calipers:The principle of the Vernier calipers is two-fold.

8 First, the slidingpiece allows the jaws to contact the sides of the object to be measured, in much the sameway as the micrometer. The distance moved by the sliding jaw is then read off the fixedruler on the main body of the instrument. The accuracy of that ruler as such, however,is only 1mm. The much improved accuracy is provided by the Vernier scale. This scaleis marked on the sliding jaw; it has 10 divisions, each subdivided into 5, ie a total of 50subdivisions. These subdivisions look like 1mmin length.

9 But if you compare the fixedand Vernier scales, you will see that the 50 subdivisions on the Vernier scale correspondto 49 subdivisions (each of 1mm) on the fixed scale! This is not a mistake but rather itis deliberately designed so that a subdivision on the Vernier scale is smaller than that onthe fixed scale by 1/50 = ; this is the accuracy of the instrument. How a readingwith this accuracy is achieved in practice is detailed below:Operation: Withnoobject between the jaws, the zeros of the Vernier and fixed scalesare coincident.

10 There is an increasing mismatch between the marks of these two scalesuntil at the end of the Vernier scale there is again coincidence between the end mark on theVernier and the 49mmmark on the fixed scale. Clearly, to obtain coincidence between thefirst subdivisions of the Vernier and of the fixed scales it would be necessary to move thesliding jaw by the deficit of ; coincidence between the second subdivisions wouldrequire 2 x = , and so on. A total of 50 x = 1mmis required to achievecoincidence between the end mark of the Vernier scale and the 50mmmark of the fixedscale.