Question

A low-frequency AC current is passed through a galvanometer. What will be the behavior of the pointer of the galvanometer?
A. The needle remains stationary at zero position.
B. The needle points to the RMS value of the AC current.
C. The needle fluctuates around zero reading with a frequency equal to the current frequency
D. The needle fluctuates around zero reading with a frequency half of the current frequency

Answer 1

Hint: A galvanometer is an electric instrument that is used to measure and indicate an electric current. A galvanometer works as an actuator. It produces a deflection according to the electric current flowing through the galvanometer. Earlier galvanometers were not calibrated now a day's calibrated galvanometer is known as Ammeter.

Complete step by step answer:
AC current is a type of current which changes its direction in every half cycle. When an AC source is connected to a galvanometer in series as shown here

A galvanometer is a current measuring instrument that measures both the magnitude as well as the direction of the current flowing through the galvanometer. Its needle will fluctuate according to the changing frequency of the AC current.
Thus the correct option which indicates the current answer to the given question is Option C.
Some important points
A moving coil galvanometer works on the principle of induction. The sensitivity of a galvanometer is the ratio of change in the position of the needle and the value of the current.
Mathematically:
Sensitivity = $\dfrac{\Delta \theta }{\Delta i}$
The more the sensitivity of the instrument less will be the chances of instrumental errors while taking the reading of the value current.

Note:
The galvanometer has an analog scaling with the initial or zero position in the center of the scale. A galvanometer can show deflection in both the direction (left and right from zero) according to the direction of the current flowing through it.