Q.

During Searle’s experiment, zero of the Vernier scale lies between 3.20×10-2 m and 3.25×10-2 m of the main scale. The 20th division of the Vernier scale exactly coincides with one of the main scale divisions. When an additional load of 2 kg is applied to the wire, the zero of the Vernier scale still lies between 3.20×10-2 m and 3.25×10-2 m of the main scale but now the 45th division of the Vernier scale coincides with one of the main scale divisions. The length of the thin metallic wire is 2 m and its cross-sectional area is 8×10-7 m2. The least count of the Vernier scale is 1.0×10-5 m. The maximum percentage error in Young’s modulus of the wire is _____.     [2014]


Ans.

(4)

Young's modulus Y=FLA×l

Here F,A and L are accurately known.

 Percentage error in Young's modulus

l=(45-20)×L.C.=25×10-5 m

ΔYY×100=Δll×100=1.0×10-525×10-5×100=4%