Question

A potentiometer having the potential gradient of $2mV/cm$ is used to measure the difference of potential across a resistance of $10\Omega$. If a length of $50cm$ of the potentiometer wire is required to get the null points the current passing through $10\Omega$ resistor is (in $mA$)

• A. $1$
• B. $2$
• C. $5$
• D. $10$

Answer 1

The correct option is D $10$

Given:- Resistance $\left(R\right)=10\Omega$

Potential gradient $\left(x\right)=2mV/cm$

Length $\left(l\right)=50cm$

According to the question;

$V=IR=xl$

$\Rightarrow$ $I\times 10=\left(\frac{2\times {10}^{-3}}{{10}^{-2}}\right)\times 50\times {10}^{-2}$

$=0.1$

$I=10\times {10}^{-3}=10mA$