Question

A tangent galvanometer has a coil with $50$ turns and radius equal to $4$ cm. A current of $0.1$ Amp is passing through it. The plane of the coil is set parallel to the earth's magnetic meridian. If the value of the earth's horizontal component of the magnetic field is $7\times {10}^{-5}T$ and ${\mu }_0=4\pi \times {10}^{-7}Wb/A-m$. then the deflection in the galvanometer needle will be :

• A. ${45}^0$
• B. ${48.2}^0$
• C. ${50.7}^0$
• D. ${52.7}^0$

Answer 1

The correct option is B ${48.2}^0$

$i=\frac{2r{B}_H}{{\mu }_{o}n}tan\theta$

$tan\theta =\frac{{\mu }_{o}ni}{2rB}=\frac{4\pi \times {10}^{-7}\times 50\times 0.1}{2\times 0.04\times 7\times {10}^{-5}}=1.121$

$\theta ={48.2}^0$