Question

3. When current of 300 u A is passed through
the coil of galvanometer, the coil is deflected
through 30°. The twist constant of the
suspension fibre is 5 x 10-'Nmper
degree. Calculate the deflecting toque acting
on coil.​

Answer 1

Answer:

15 x 10^-8 Nm

Explanation:

Deflecting torque acting on coil ,

torque = K x Theta

= 5 x 10^-9 x 30°

= 15 x 10^-8 Nm.

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Answer 2

Given:

Current of 300 u A is passed through the coil of galvanometer, the coil is deflected through 30°. The twist constant of the suspension fibre is 5 x 10^(-9) Nm/degree.

To find:

Deflecting Torque ?

Calculation:

In a Moving-Coil Galvanometer, the Deflecting Torque is equal to the Restoring Torque , such that:

$\sf \therefore \: \tau_{(deflecting)} = \tau_{(restoring)}$

$\sf \implies\: \tau_{(deflecting)} = k \times \theta(in \: degree)$

$\sf \implies\: \tau_{(deflecting)} = 5 \times {10}^{ - 9} \times 30$

$\sf \implies\: \tau_{(deflecting)} = 15 \times {10}^{ - 8} \: Nm$

So, the final answer is:

$\boxed{ \bf\: \tau_{(deflecting)} = 15 \times {10}^{ - 8} \: Nm}$

• Please note that the "current" value is given to confuse the students, because it can be used only when other parameters like Area of coil, Number of coils and Magnetic Field has been provided.

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