Two parallel conductors carrying current in the same direction attract each other. If they are permitted to move toward each other, the forces of attraction do work. From where does the energy come from? Does this contradict the assertion in the previous chapter that magnetic forces on moving charges do no work? Explain.

Explanation:

The energy comes form the magnetic force acting on both the wires. As they attract each other so they travel some distance due to which work is there and this work is converted into energy.

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.