Question

Figure shows a coil C connected to a galvanometer G. When the North-pole of a bar magnet is pushed towards the coil, the pointer in the galvanometer deflects. Regarding this set up, the following statements are given:
(A) It indicates the presence of electric current in the coil.
(B) The deflection is found to be smaller when the magnet is pushed towards the coil faster.
(C) There is repulsion in the moving magnet and the magnetic pole induced in the coil facing towards the N pole of the magnet.
(D) If the bar magnet does not move, there is no induced current in the coil.
Choose the correct answer from the options given below:
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• A. (A), (C) and (D) only
• B. (A), (B) and (C) only
• C. (A), (B), (C) and (D)
• D. (B), (C) and (D) only

Hint:

Remember the core principles: 1. Faraday's Law: Changing magnetic flux induces an EMF. Faster change = larger EMF. 2. Lenz's Law: The induced current opposes the change in flux. (Nature abhors a change in flux!) This determines the direction of the current and the nature of the force (attraction or repulsion).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question tests the understanding of electromagnetic induction, specifically Faraday's Law of Induction and Lenz's Law. Faraday's Law relates the change in magnetic flux to the induced electromotive force (EMF), and Lenz's Law gives the direction of the induced current.

Step 2: Detailed Explanation:
Let's analyze each statement:
(A) It indicates the presence of electric current in the coil.
A galvanometer is a device that detects electric current. The deflection of its pointer is a direct indication that a current is flowing through the coil. This statement is correct.
(B) The deflection is found to be smaller when the magnet is pushed towards the coil faster.
According to Faraday's Law of Induction, the magnitude of the induced EMF (and hence the induced current and galvanometer deflection) is directly proportional to the rate of change of magnetic flux (\(|\mathcal{E}| \propto |d\Phi_B/dt|\)). Pushing the magnet faster increases the rate of change of flux, which results in a larger induced current and a larger deflection. This statement is incorrect.
(C) There is repulsion in the moving magnet and the magnetic pole induced in the coil facing towards the N pole of the magnet.
According to Lenz's Law, the induced current flows in a direction that opposes the change that produced it. As the North pole of the magnet approaches the coil, the magnetic flux through the coil increases. To oppose this increase, the coil must generate a magnetic field pointing away from the magnet. This means the face of the coil nearer to the magnet becomes a North pole. Since like poles repel, there will be a repulsive force between the coil and the magnet. This statement is correct.
(D) If the bar magnet does not move, there is no induced current in the coil.
For an EMF to be induced, there must be a change in the magnetic flux through the coil. If the magnet is stationary relative to the coil, the magnetic flux is constant (\(d\Phi_B/dt = 0\)). Therefore, no EMF is induced, and no current flows. This statement is correct.

Step 3: Final Answer:
Statements (A), (C), and (D) are correct, while (B) is incorrect. Therefore, the correct option includes only (A), (C), and (D).