Question

An electric iron consumes energy at a rate of $880W$ when heating is at the maximum rate and $330W$ when the heating is at the minimum. The voltage is $220V$. What are the current and the resistance in each case.

Answer 1

Power $=VI=\frac{V^2}{R}$, Where $V$ is voltage, $I$ is current , $R$ is resistance.

First case,

Power$=880W$ $\Rightarrow 880=220\times I$ $\Rightarrow I=4A$

$\Rightarrow 880=\frac{{220}^2}{R}$ $\Rightarrow R=55\Omega$

Second Case,

Power $=440W=220\times I$ $\Rightarrow I=2A$

$\Rightarrow 440=\frac{{220}^2}{R}$ $\Rightarrow R=110\Omega$