Question

Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is

• A. 40Ω
• B. 250Ω
• C. 25Ω
• D. 500Ω

Answer 1

The Correct Option is B

To find the resistance of the galvanometer, we use the relation between current sensitivity, voltage sensitivity, and resistance.

• Current sensitivity: \( S_c = \frac{\theta}{I} \)
• Voltage sensitivity: \( S_v = \frac{\theta}{V} \)
• Relation: \( S_v = \frac{S_c}{R} \)

Given:

• \( S_c = 5\,\text{div/mA} \)
• \( S_v = 20\,\text{div/V} \)

Unit Conversion:

\( S_c = 5\,\text{div/mA} = 5 \times 10^3\,\text{div/A} = 5000\,\text{div/A} \)

Calculation:

\[ S_v = \frac{S_c}{R} \Rightarrow 20 = \frac{5000}{R} \]

\[ R = \frac{5000}{20} = 250\,\Omega \]

Final Answer: \( 250\,\Omega \)