Question

Statement 1: An external agent makes a charge move through an electric field for some duration. After the duration, its kinetic energy is equal to what it was before the duration.
Statement 2: No work was done by the field.
Statement 2 is

• A. True.
• B. False.

Answer 1

The correct option is B False.

According to the work energy theorem, the net work done on an object is equal to the change in its kinetic energy. Please notice the word ‘net work done’! When we say ‘net work done’ we mean work done because of all the forces on the body or in other words the work done because of the ‘net’ force. Here the question says that the kinetic energy remains the same i.e. the change in kinetic energy is zero. Now according to the work energy theorem, the net work done must be zero. As the external agent ‘makes’ the charge move, it does some work on it, so the work done by the field must be equal and opposite in sign as the net work done must be zero. So the field does do work.