Describe a method to determine Young's modulus of the material of a thin wire.
Answers
Answer:
Solution :
Apparatus : The experimental wire B is suspended from a rigid wallsupport along with a compensating or reference wire A of the same length, material and cross section.
A manin scale is attached to the wire A. Avernier scale attached to the wire B can move alongside the main scale.
A dead load is attached to the compensating wire to keep it taut. Slotted weights may be added to a hanger attached to the experimental wire.
Procedure:
(1) The length L and radius r of the experimental wire are measured.
(2) The experimental wire is initially loaded with 1 kg to 2 kg to keep it taut and free from kinks. It is treated as a zeroload. The main scale and Vernier scale readings are noted as those for zero-load.
(3) The stretching load Mg on the experimental wire is increased by 0.5 kg at a time. the scale readings are noted for each increase in load, after allowing sufficient time for the wire to elongate.
(4) After 6-8 such readings, the wire is unloaded 0.5 kg at a time, and the corresponding scale readings are noted. Within limits of experimental error, the readings for the same load-while loading and unloading- should be the same.
(5) The average elongation per unit mass, ΔL/M is found.
(6) Young's modulus of the material of the wire is calculated using the formula
Y=longitudinal stresslongitudinal strain=Mg/πr2ΔL/L=gLπr2(ΔL/M)