Single Choice

A moving coil galvanometer has 48 turns and area of coil is $$\displaystyle 4\times { 10 }^{ -2 }{ m }^{ 2 }$$. If the magnetic field is 0.2T, then to increase the current sensitivity by 25% without changing area (A) and field (B) the number of turns should become :

A24
B36
C60
Correct Answer
D54

Solution

The Torque equation for moving coil galvanometer is given as,
$$k\phi=NIAB$$

As sensitivity $$S$$ is proportional to deflection per-unit current,
$$S\propto \phi/I=NAB/k$$

Thus, to increase sensitivity by 25% without changing $$A\ or\ B$$,
We need to increase $$N$$ by 25%

So, $$N_{new}=1.25\times N=1.25\times48=60$$
Option C is correct.

SIMILAR QUESTIONS

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