Question:medium

A current of \( 200 \, \mu\text{A} \) deflects the coil of a moving coil galvanometer through \( 60^\circ \). The current to cause deflection through \( \frac{\pi}{10} \, \text{radian} \) is:

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The deflection angle in a moving coil galvanometer is proportional to the current passing through it. Always use the proportionality relation \( \frac{I_2}{I_1} = \frac{\theta_2}{\theta_1} \) to calculate unknown currents when deflection angles are given.
Updated On: Nov 26, 2025
  • \( 30 \, \mu\text{A} \)
  • \( 120 \, \mu\text{A} \)
  • \( 60 \, \mu\text{A} \)
  • \( 180 \, \mu\text{A} \)
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The Correct Option is C

Solution and Explanation

The deflection of a moving coil galvanometer is directly proportional to the current flowing through it, expressed as \( I \propto \theta \). Given: \( I_1 = 200 \, \mu\text{A} \) \( \theta_1 = 60^\circ \) \( \theta_2 = \frac{\pi}{10} \) Convert \( 60^\circ \) to radians: \( \theta_1 = 60^\circ = \frac{\pi}{3} \) radians. Applying the proportionality: \( \frac{I_2}{I_1} = \frac{\theta_2}{\theta_1} \) Substitute known values: \( \frac{I_2}{200 \, \mu\text{A}} = \frac{\frac{\pi}{10}}{\frac{\pi}{3}} \) Simplify the ratio of angles: \( \frac{I_2}{200 \, \mu\text{A}} = \frac{3}{10} \) Calculate \( I_2 \): \( I_2 = 200 \, \mu\text{A} \cdot \frac{3}{10} = 60 \, \mu\text{A} \) Final Answer: \( \boxed{60 \, \mu\text{A}} \)
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