Question

In the moving coil galvanometer, if number of turns in the coil is doubled, then the current sensitivity ______ and the voltage sensitivity ______.

• A. remains unchanged, will be doubled
• B. will be halved, will be doubled
• C. will be doubled, remains unchanged
• D. will be halved, remains unchanged

Hint:

Increasing turns is a great way to detect smaller \textbf{currents}, but it won't help you detect smaller \textbf{voltages} because the extra wire adds extra resistance.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Current Sensitivity ($I_s$) is $\frac{NBA}{k}$. Voltage Sensitivity ($V_s$) is $\frac{NBA}{kR}$.
Step 2: Detailed Explanation:
1. Current Sensitivity: $I_s \propto N$. If turns ($N$) are doubled, $I_s$ is doubled.
2. Voltage Sensitivity: $V_s = \frac{I_s}{R}$. When $N$ is doubled, the length of the wire doubles, which also doubles the resistance ($R$).
Since both the numerator ($I_s$) and denominator ($R$) double, the ratio remains constant.
Step 3: Final Answer:
Current sensitivity doubles, but voltage sensitivity remains unchanged.