For a heater rated at $4kW$; $220V$ . Calculate the resistance of the heater element.

Given:   $V=220$ volts       $P=4000$ W

Electric power is given by

$P=\frac{V^2}{R}$    where $R$ is resistance and $V$ is voltage.

$\therefore$ Resistance of the heater      $R=\frac{V^2}{P}=\frac{220^2}{4000}=12.1\Omega$