A body is moved along a closed loop. Is the work done in moving the body necessarily zero? If not, state the condition under which work done over a closed path is always zero?
Only when the conservative force acts along the body when it moves in a closed loop. The work done can be zero. However, if a non-conservative force acts on the body when it moves in a loop (for example friction, electrostatic force, etc.), then the work done cannot be zero.