Question

Potential energy of a system of positive charges arranged like a ring is:

Statement 1: Work done (without providing any Kinetic energy to any charge) by an external force in bringing each charge from infinity to the final configuration i.e. a ring.

Statement 2: Work done (without providing any Kinetic energy to any charge) by an external force in bringing each charge from reference point to the final configuration i.e. a ring.

• A. Both statement 1 and 2 are correct
• B. Statement 1 is correct but statement 2 is wrong
• C. Statement 1 is wrong but statement 2 is correct
• D. Both statement 1 and 2 are wrong

Answer 1

The correct option is A Both statement 1 and 2 are correct

Potential energy of any system is always defined with respect to a reference point. By definition, potential energy is the amount of work done in creating a system. By creating a system, we mean ‘bringing all the constituent charges of the system (without acceleration) from some reference point to the configuration of the system. As there is no acceleration, there is no change in velocity and thus no change in kinetic energy. If this reference point happens to be infinity then it’s ‘potential energy with respect to infinity or by convention we call it just the ‘potential energy’ of the system.