Question

What is meant by 'relaxation time' of free electrons in a conductor ? Show that the resistance of a conductor can be expressed by R = ml/(ne²τA), where symbols have their usual meanings.

Draw the circuit diagram of a Wheatstone bridge. Obtain the condition when no current flows through the galvanometer in it.

Derive the relation between the current and the drift velocity of free electrons in a conductor. Briefly explain the variation of resistance of a conductor with rise in temperature.

An ammeter, together with an unknown resistance in series is connected across two identical batteries, each of emf 1·5 V, connected (i) in series, and (ii) in parallel. If the current recorded in the two cases be (1/2) A and (1/3) A respectively, calculate the internal resistance of each battery.