Question

A 1000w heater is rated to operate at a direct current of 10a if the heater is supplied alternating current for producting the same quantity of heat the value of current shoud be

Answer 1

Explanation:

An electric heater is in the form of a coil of ohmic resistance R and inductance L. On d.c. supply, resistance=R. On a.c. supply, impedance=√(R^2+(wL) ^2), which is obviously more.

When potential difference is constant, heat produced/sec is inversely proportional to resistance. Hence heat produced/sec in case of a.c. will be less compared to heat produced/sec in case of d.c.