What form of energy does a compressed spring have ?

Where does the chemical energy stored in your muscles come from ?

What energy transfers take place when you turn on a torch ?

In terms of energy, what happens when you burn a fuel ?

What happens to the wasted energy in a light bulb ?

Why should we talk about energy being 'wasted' not being 'lost' ?

In a light bulb, for every 25 joules of energy that are supplied to the bulb, 5 joules are usefully transferred into light energy. What is the efficiency of the light bulb ?

A machine is adjusted so that it wastes less energy because of friction. What happens to the Efficiency of the machine ?