(a) Explain about non-linear resistors with some examples and illustration on how they differ from linear resistor. (6)

(b) A single phase transformer has 100 turns on the primary and 200 turns on the secondary. The no load current is 3 Ampere at a power factor of 0.2 lagging. Calculate the primary current and power factor when the secondary current is 280 A at a power factor of 0.8 lagging. (10)