Question

A $4kW$ heater is connected to a $220V$source of power. Calculate

i. the electric current passing through the heater

Answer 1

Step 1- Given Data and formulas

The power rating of the heater $P=4kW$

The voltage applied $V=220V$

Electric power in terms of the voltage applied and resistance is given by

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

where $R$ is the resistance.

Step 2: Finding the resistance of the heater

Substitute the known values in the equation

$$\begin{gathered} 4kW\times \frac{1000W}{1kW}=\frac{{(220V)}^2}{R} \\ R=\frac{{220}^2}{4000} \\ R=12.1\Omega \end{gathered}$$

Step 3: Finding the electric current passing through the heater

According to Ohm's law,

$V=IR$

Where $I$ is current.

Substitute the values of the applied voltage and resistance

$$\begin{gathered} 220V=I\times 12.1\Omega \\ I=\frac{220}{12.1} \\ I=18.18A \end{gathered}$$

Final answer: The electric current passing through the heater is $18.18A$.