Question

A galvanometer of resistance $50\Omega$ is connected to a battery of $8V$ along with a resistance of $3950\Omega$ in series. A full scale deflection of $30$ div is obtained in the galvanometer. In division, the resistance in series should be ____ $\Omega$.

• A. $1950$
• B. $7900$
• C. $2000$
• D. $7950$

Answer 1

The correct option is A $1950$

Total resistance $=50+3950=4000\Omega$
For this circuit, deflection of $\alpha$- resistance
$\Rightarrow \frac{4000}{R}=\frac{30}{15}$
$\Rightarrow R=\frac{4000}{R}=2000\Omega$
Then, resistance should be in series
$=2000-50=1950\Omega$.