Question

A tangent galvanometer has a coil of 25 turns and a radius of 15 cm. The horizontal component of the earth's magnetic field is $3\times {10}^{-5}T.$ The current required to produce a deflection of ${45}^0$ in it is:

• A. 0.14 A
• B. 0.29 A
• C. 1.2 A
• D. $3.6\times {10}^{-5}\text{A}$

Answer 1

The correct option is B 0.29 A

In a tangent galvanometer,

$i=\frac{2r{B}_H}{{\mu }_{0}N}\tan \theta \therefore i=\frac{2\times 15\times {10}^{-2}\times 3{\times 10}^{-5}}{4\pi {\times 10}^{-7}\times 25}\times \tan 45°=0.29A$