Energy can exist in several forms and may change from one form to another. For each of the following, state the energy changes that occur in:

(a) the unwinding of a watch spring

(b) a loaded truck when started and set in motion

(c) a car going uphill

(d) photosynthesis in green leaves

(e) charging of a battery

(f) respiration

(g) burning of a match stick

(h) explosion of crackers

State the energy changes in the following cases while in use:

(a) Loudspeaker

(b) A steam engine

(c) Microphone

(d) Washing machine

(e) A glowing electric bulb

(f) Burning coal

(g) A solar cell

(h) Biogas burner

(i) An electric cell in a circuit

(j) A petrol engine of a running car

(k) An electric iron

(l) A ceiling fan

(m) An electromagnet.

Is it practically possible to convert a form of energy completely into the other useful form? Explain your answer.

Define the term potential energy of a body. Name its two forms and give one example of each.