18
Question Question 18
State the energy changes that occur in the following:
(i) The unwinding of a watch spring.
(ii) Burning coal while operating a steam engine
(iii) Lighting of a torch bulb.
(iv) An electric generator (or dynamo).
(i) During the unwinding of a watch spring, the potential energy changes into kinetic energy.
(ii) In a steam engine chemical energy of coal first changes into heat energy which is transferred to steam. Then the heat energy of steam changes into mechanical energy which causes the train to move.
(iii) When torch bulb is lighted, chemical energy of batteries change into light and heat energy.
(iv) In an electric generator (dynamo) mechanical energy changes into electrical energy.