Question

Consider a moving coil galvanometer (MCG):
A : The torsional constant in moving coil galvanometer has dimensions \( [ML^2 T^{-2}] \)
B : Increasing the current sensitivity may not necessarily increase the voltage sensitivity.
C : If we increase the number of turns (N) to its double (2N), then the voltage sensitivity doubles.
D : MCG can be converted into an ammeter by introducing a shunt resistance of large value in parallel with the galvanometer.
E : Current sensitivity of MCG depends inversely on the number of turns of the coil.
Choose the correct answer from the options given below:

• A. A, B only
• B. A, D, only
• C. B, D, E only
• D. A, B, E only

Hint:

To determine the behavior of an MCG, remember that voltage sensitivity and current sensitivity depend on factors like the number of turns, torsional constant, and the shunt resistance, which can modify its properties.

Answer 1

The Correct Option is A

We need to evaluate the correctness of each statement:
(A) The torsional constant in moving coil galvanometer has dimensions \( [ML^2 T^{-2}] \):
This statement is correct. The torsional constant \( \tau \) is given by \( \tau = C \theta \), where \( \theta \) is the angular deflection, and \( C \) is the constant. The dimensions of \( C \) are \( [ML^2 T^{-2}] \).
(B) Increasing the current sensitivity may not necessarily increase the voltage sensitivity:
This statement is correct. Increasing the current sensitivity does not always imply that the voltage sensitivity will increase, as they depend on different factors.
(C) If we increase the number of turns (N) to its double (2N), then the voltage sensitivity doubles:
This statement is incorrect. The voltage sensitivity is proportional to the number of turns \( N \), but it is not doubled when \( N \) is doubled; it depends on other factors as well.
(D) MCG can be converted into an ammeter by introducing a shunt resistance of large value in parallel with the galvanometer:
This statement is correct. To convert a galvanometer into an ammeter, we can introduce a shunt resistance in parallel to bypass most of the current.
(E) Current sensitivity of MCG depends inversely on the number of turns of the coil:
This statement is incorrect. The current sensitivity of MCG is directly proportional to the number of turns of the coil, not inversely.
Therefore, the correct answer is option (1): A, B only.