Question

A resistor develops heat at the rate of 20W when the potential difference across its ends is 30V. What is the resistance of the resistor?

Answer 1

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

$P=20\:W$

$V=30v$

$20=\frac{30^2}{R}= \frac{900}{R}$

$R=\frac{900}{20}=45\Omega$