Hooke's Law

What was the extension when the force applied was 12 N?

When the force is from 0 to 16 N, the wire should obey Hooke's law.

So, the extension = 12 X 0.5/4 = 1.5 mm


i. The wire would restore its original length.

ii. The wire would restore its length, but not its original length. The length of the wire after unloading the force should be greater than the initial length.

The reason for (i) is that the wire has not reached the proportional limit. So, the wire obeys Hooke's law. All the force acting on the wire is conservative. So, it restore its own original length.

The reason for (ii) is that the wire has been extended over its proportional limit. When the force is removed, it will restore its length but there is a permanent set on the wire.


By E = Fl / Ae

For copper wire, the Young Modulus E should be the same.

For the same diameter, which means the same cross-sectional area.

So, for the greater length, it will lead to greater extensions of the wire.


The elastic limit is not affected. It remains the same.