A control circuit of hair dryer is designed. The sine input voltage of hair dryer is 50 Hz and 220 v. two resistors and position switches are required in the control circuit to realize three positions of 250 W, 500 W and 1000 W respectively. The equivalent circuit of switch in three positions of high, medium and low is drawn, and the component parameters are given

A control circuit of hair dryer is designed. The sine input voltage of hair dryer is 50 Hz and 220 v. two resistors and position switches are required in the control circuit to realize three positions of 250 W, 500 W and 1000 W respectively. The equivalent circuit of switch in three positions of high, medium and low is drawn, and the component parameters are given

1000W heating wire resistance = 48.4 Ω, current = 4.54a
500W, current = 3.227a, series resistance 20.57 Ω, resistance power 210W (w = the square of I multiplied by R)
250W, current = 2.3A, series resistance 48 Ω, resistance power 250W
This circuit is not practical
Using resistance to reduce power, the extra power will be emitted from the resistance. It can't reduce the temperature much, but it needs high power resistance
The actual circuit is to add half wave rectification to reduce the power to 1 / 4,