A coil $C_1$ is connected to a galvanometer G. Second coil $C_2$ is connected to a battery through a tapping key. The steady current in the coil $C_2$ produces a steady magnetic field. As coil $C_2$ is moved towards the coil $C_1$, the galvanometer shows a deflection. To obtain a large deflection, one or more of the following steps can be taken:
(A) Use a rod made of soft iron inside the coil $C_2$
(B) Connect the coil $C_2$ to a more powerful battery
(C) Move the arrangement of coil $C_2$ rapidly towards the coil $C_1$
(D) hold the key pressed continuously
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (C) only
Galvanometer shows deflection due to **change in magnetic flux** through coil C1. According to Faraday's law, induced emf is proportional to the rate of change of magnetic flux:
$\mathcal{E} = -\frac{d\Phi_B}{dt}$
To obtain a large deflection:
(A) Use a soft iron core inside C2 ✅ (increases magnetic field strength)
(B) Connect C2 to a more powerful battery ✅ (increases current → stronger magnetic field)
(C) Move C2 rapidly towards C1 ✅ (increases rate of change of flux)
(D) Hold the key pressed continuously ❌ (steady magnetic field gives no change → no deflection)
Correct steps: A, B, C