(i) Define resonant vibrations.

(ii) Which characteristic of sound, makes it possible to recognize a person by his voice without seeing him ?

Calculate the effective resistance across AB :

(i) State whether the specific heat capacity of a substance remains the same when it's state changes from solid to liquid.

(ii) Give one example to support your answer.

How does an increase in the temperature affect the specific resistance of a :

(i) Metal and

(ii) Semiconductor?