Q. Consider a moving coil galvanometer (MCG): A. The torsional constant in moving coil galvanometer has dimensions $[ML^2T^{-2}]$ B. Increasing the current sensitivity may not necessarily increase the voltage sensitivity. C. If we increase 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 galvanometer. E. Current sensitivity of MCG depends inversely on number of turns of coil. Choose the correct answer from the options given below:
A) A, D Only
B) A, B, E Only
C) B, D, E Only
D) A, B Only
Explanation
[Solution by Dr. Abubacker] A: $\tau=C\theta$, so $C$ has the dimension of torque, $ML^2T^{-2}$ (true). B: current sensitivity $\frac{NBA}C$ rises with $N$, but the coil resistance rises too, so voltage sensitivity need not rise (true). C: doubling $N$ doubles the resistance as well, leaving voltage sensitivity unchanged (false). D: an ammeter needs a small shunt (false). E: current sensitivity is directly proportional to $N$ (false). So A and B only. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.