Question

A torch bulb Is rated at $3V$ and $600mA$. Calculate it’s power and resistance.

Answer 1

Step 1: Given

Voltage rating of torch = $3V$

Current rating of torch = $600mA=0.6A$

Step 2: Formula used and calculation

Power is given by

$$\begin{gathered} P=VI \\ =3\times 0.6W \\ =1.8W \end{gathered}$$

Thus, the power of the torch is $1.8W$.

Resistance is given by

$$\begin{gathered} R=\frac{V^2}{P} \\ =\frac{3^2}{1.8}\Omega \\ =5\Omega \end{gathered}$$

Hence, the resistance of the torch is $5\Omega$.