How do amplifier work to produce sound energy?

Think of coal like wood. In a wood stove or furnace, wood is burned to produce heat. Coal contains more energy and is cheaper that wood, however wood is renewable. The large coal power plants that...

by the vibration of the whole bell , it makes a sound

through potatoes

A sound (audio) amplifier works by making a larger copy, or series of copies, of a weak signal.

First of all, remember that energy can't be created. It can only be converted from one form to another, and moved from one place to another. The electrical generator doesn't create or "produce" any...