Question

A $1kW$ heater is meant to operate at $200V$. What is its resistance?

Answer 1

Power is given by
$P=\frac{V^2}{R}$
where $V$ is the voltage, $P$ is the power, $R$ is the resistance.
Thus,
$R=\frac{{200}^2}{1000}\Omega$

$\Rightarrow R=40\Omega$