Question

When a $9V$ battery is connected across an unknown resistor, there is a current of $3mA$ in the circuit. Find the value of the resistance of the resistor.

Answer 1

Step 1- Given data and formula

1. Potential difference $V=9V$
2. Current $I=3mA$ or $I=3\times {10}^{-3}A$

(Note: $1mA={10}^{-3}A$)

Consider the resistance of the resistor is $R$.

The formula for $R$ is

$R=\frac{V}{I}$

Step 2- Finding the resistance of the resistor

Substituting the known values,

$$\begin{gathered} R=\frac{V}{I} \\ R=\frac{9V}{3\times {10}^{-3}A} \\ R=3000\Omega \end{gathered}$$

Hence, the value of the resistance of the resistor is $3000\Omega$.