Question

A wire-wound resistor with a resistance of 250ohm will overheat if the power dissipated exceeds 10W. What is the maximum constant voltage V that can be applied across the terminals of this resistor?

Answer 1

$P=IU, I=\frac {U}{R} \implies\\ P=\frac{U^2}{R}\implies U=\sqrt{PR}\implies\\ U=\sqrt{10\cdot250}=\sqrt{2500}=50 \textnormal{v}\\ answer: U=50\textnormal{volt}$