Heat is transferred only when there is a ______________ .
Hence, heat is transferred only when there is a temperature difference.
Name the energy transfer which occurs when :
(a) an electric bell rings
(b) someone speaks into a microphone
(c) there is a picture on a television screen
(d) a torch is on
When heat is transferred to a substance, its temperature_______.
Latent heat comes into the picture only when there is a change of state.