Question

If the number of turns in a moving coil galvanometer of current sensitivity $C$ and voltage sensitivity $V$ is doubled, then

• A. $C$ remains unchanged and $V$ is doubled
• B. both $C$ and $V$ are halved
• C. both $C$ and $V$ are doubled
• D. $C$ is doubled and $V$ remains unchanged
• E. both $C$ and $V$ remain unchanged

Answer 1

Answer: (D)

Current sensitivity, $C = \frac{NAB}{k}$
Voltage sensitivity, $V = (\frac{NAB}{k})\frac{I}{R}$
If $N \to 2N$ i.e., doubled the number of turns, then $C \to 2C$
Thus, the current sensitivity doubles.
If $N \to 2N$. then $R \to 2R$,
$\therefore V \to V$
Thus, the voltage sensitivity remains unchanged.