Question

The power dissipated in a resistor is 240 watts when a voltage of 220 volts is across it. If the voltage is cut in half, what is the power dissipation in the resistor?

Answer 1

$P= \frac{V^2}{R}$

Where P= power

V= voltage

R= resistance

For a constant resistance, $P\propto V^2$

When voltage is cut in $\frac{1}{2}$

Power is cut in $(\frac{1}{2})^2$

New Power= $(\frac{1}{2})^2×240=60W$