Question

A moving coil galvanometer has 48 turns and area of coil is $4\times {10}^{-2}{m}^2$. If the magnetic field is 0.2T then to increase the current sensitivity by 25% without changing area and B, the no.of turns should become

• A. 20
• B. 30
• C. 40
• D. 60

Answer 1

The correct option is D 60

$\frac{\theta }{i}\alpha n\frac{\theta }{i}=S$ sensitiveitly
$\frac{S_1}{S}=\frac{n_1}{n};\frac{125}{100}=\frac{n_1}{48};\frac{5}{4}=\frac{n_1}{48}{n}_1=5\times 12n_1=60$