A hot plate with regulated power is designed for a voltage of 220 V and has two spiral heater elements of 120 ohm and 60 ohm resistance, respectively. Devise a circuit diagram which would enable the plate to operate at three power-outputs: of 400 W, 800 W and 1200 W.

Explanation

The circuit shown in the diagram of Fig. 26.17 enables any one of the three powers desired to be obtained.