Question

Two coils $A$ and $B$ are placed parallel to each other at a very small distance apart. The coil $A$ is connected to an A.C. supply. $G$ is a very sensitive galvanometer. When the key $K$ is closed.

• A. A constant deflection will be observed in the galvanometer for a $50Hz$ supply
• B. Small variations will be observed in the galvanometer due to applied voltage of $50Hz$
• C. Oscillations in the galvanometer may be observed when the input a.c. voltage has a frequency of $1$ to $2Hz$
• D. No variations will be observed in the galvanometer even when the input a.c. voltage has a frequency of $1$ to $2Hz$

Answer 1

Answer: (C)

Oscillations in the galvanometer may be observed when the input a.c. voltage has a frequency of $1$ to $2Hz$

When an alternating current passes through the coil $A$, there will be induced emf of opposite polarity in $B$. If $50Hz$ is used, the motors will be so fast, one may not be observe them. If the frequency is small, one can observe them.