Question

A dual voltage/dual resistance AC hair dryer can be used with a 120 V or 230 V power supply. A switch allows the user to set the voltage (and hence the resistance) to the appropriate value. A tourist takes her 1530 W dual voltage hair dryer to Europe. She forgets to set the switch to 230 V. What power does the hair dryer consume before it starts to smoke?____________ W

Answer 1

Answer:

The power is  $p= 5621 W$

Explanation:

In order to obtain the power it consumes we need to first obtain the resistance of the hair dryer at 120 V

                  $R = \frac{V^2}{P} = \frac{(120 V)^2}{1530W} = 9.411 \Omega$

Now the power supplied in Europe at their voltage of 230V would be

                           $P = \frac{V^2} {R} = \frac{(230V)^2}{9.411 \ \Omega} = 5621 W$

Looking the power obtain we see that it is higher than 1530 W so this would cause the dryer to smoke.