99 Percentile Qs Bank for JEE MainPhysicsWork, Power and Energy
When a steel wire fixed at one end is pulled by a constant force F at its other end, its length increases by l . Which of the following statements is not correct?
Options
- AWork done by the external force is F l .
- BSome heat is produced in the wire in the process.
- CThe elastic potential energy of the wire is F l 2 .
- DThe heat produced is equal to half of the elastic potential energy stored in the wire.
Correct answer
D. The heat produced is equal to half of the elastic potential energy stored in the wire.
Step-by-step solution
Given that Elongation in wire = l Let Young' modulus of wire = Y Let Length of wire = L Let area of wire = A Applied force = F Elastic wire behaves as a spring whose force constant is equal to k = Y A L Work done by spring is given by, W = 1 2 k x 2 ∴     F = k x ⇒     W = 1 2 F x ∴     x = l ⇒   W = 1 2 F l Work done by applied force W force = force   × displacement ⇒   W force = F l Potential energy stored in wire U = 1 2 k x 2 &#