Draw the circuit diagram of a full wave rectifier. Briefly explain its working.

Draw the circuit diagram of the set-up used to study the characteristic of a $\mathrm{NPN}$ transistor in its common emitter configuration. Sketch the typical input characteristic.

Draw the circuit diagram of the set-up used to study the characteristic of a $\mathrm{NPN}$ transistor in its common emitter configuration. Sketch the typical output characteristic for this transistor configuration. How the output characteristics be used to calculate the 'current gain' of the transistor?