PHYSICS LAB

VERNIER CALLIPERS It consists of 1.Main Scale (graduated in cm/mm) 2.Vernier Scale

*Least count is the minimum possible length, that can be measured from that apparatus. *If N div. Of V.S. are equal in length to (N-1) M.S.div. Then L.C.=1M.S.-1V.S. [ 1-(N-1)/N ] ms =1ms/N *Reading of Vernier Caliper will be: M.S. reading + (V.S. reading*L.C.)

*What is the length of this piece of chalk?

ZERO ERROR Positive error Negative error Corrections are done opposite to the error.

Screw gauge  There are two scales: 1.Main scale, graduated along the axis of the screw. 2.Cap scale/Head scale (H).

Image: A typical micrometer.

PRINCIPLE: The linear distance moved by the screw head is directly proportional to the amount of rotation given to the screw.  Distance moved on sleeve by screw, after giving one complete revolution is called Pitch.  Let there be ‘N’ divisions on circular scale and on ‘n’ complete rotations screw shifts by one sleeve unit, then Least Count can be given by 1/(n*N).

Thus reading of micrometer can be given by M.S. reading + (C.S. reading*L.C.)

*Here readings has been written in decimeters.

When Spindle touches Anvil, indicator of ‘0’ on circular scale should touch the main scale line at ‘0’. If this doesn’t happen, we call it error (positive/negative).

If the Thimble is yet to reach ‘0’ on main scale, it is positive error and if it has passed that point, it is negative error. Correction is made to satisfy error.

* What is the reading of this micrometer? Given that there are 50 divisions on circular scale. *What if the zero error is -0.25?

SPECIFIC HEAT OF LIQUID USING CALORIMETER  JUST GO THROUGH THE CHAPTER OF CALORIMETRY IN H.C.VERMA’S BOOK.THE PRINCIPLE OF CALORIMETRY IS SIMPLY APPLIED.  ERROR ANALYSIS CAN BE DONE BY THE GENERAL METHOD.

V=I/R  R/R=  V/V+  I/I OHM’S LAW

METER BRIDGE  P/Q = L 1 /(100- L 1 )  ERROR  END-CORRECTION

POST OFFICE BOX S=(P/Q)xR

FOCAL LENGTH OF A CONCAVE MIRROR AND A CONVEX LENS (u-v method)  Formulae :-  mirror : (1/f)=(1/v) + (1/u)  Lens:(1/f)=(1/v) + (1/u) Generalizing, the slope of (1/IvI) vs. (1/IuI) gives a straight line, whose intercept equals (1/IfI).  GIVEN u, v from experimental data, f can be calculated.  ERROR: take log and then differentiate.

Searle’s method for finding Young’s Modulus  Finding the slope of stress vs. strain graph, tan θ = l/W=l/mg  Stress = mg/Лr 2  Strain = l/L  Y=stress/strain = L/(Лr 2 tan θ)  ERROR