Question

If a current of 500 mA produces a deflection of $30^{\circ }$ in a tangent galvanometer, then the current that produces a deflection of $60^{\circ }$ is

• A. 1. 5 A
• B. 1 A
• C. 500 mA
• D. 866 mA
• E. 2A

Answer 1

Answer: (A)

If an electric current I is flowing through the coil of the tangent galvanometer and the magnetic needie gets deflected and comes to rest making an angie $\theta$ with the direction of horizontaI component of earth's magnetic field H, then for the tangent galvanometer
$I=K\tan \theta$
where K is the reduction factor of tangent galvanometer.
$\therefore \frac{I_1}{I_2}=\frac{tan{\theta }_1}{\tan {\theta }_2}$
or $\frac{500}{I_2}=\frac{\tan 30^{\circ }}{\tan 60^{\circ }}$ or $\frac{500}{I_2}=\frac{\left(\frac{1}{\sqrt{3}}\right)}{\sqrt{3}}$
or $\frac{500}{I_2}=\frac{1}{3}$
or $I_2=1500mA=1.5A$