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: Conceptual Foundation:
This inquiry evaluates comprehension of electromagnetic induction, specifically Faraday's Law of Induction and Lenz's Law. Faraday's Law quantifies the relationship between magnetic flux variation and induced electromotive force (EMF), while Lenz's Law determines the direction of induced current.

Step 2: In-depth Analysis:
Examination of each assertion is as follows:
(A) It indicates the presence of electric current in the coil.
A galvanometer serves to detect electric current. Pointer deflection directly signifies current flow through the coil. This statement is valid.
(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 induced EMF (and consequently, induced current and galvanometer deflection) is directly proportional to the rate of magnetic flux change (\(|\mathcal{E}| \propto |d\Phi_B/dt|\)). Accelerating the magnet's movement intensifies the rate of flux change, leading to a greater induced current and a larger deflection. This statement is invalid.
(C) There is repulsion in the moving magnet and the magnetic pole induced in the coil facing towards the N pole of the magnet.
Lenz's Law mandates that the induced current opposes the change that generated it. As the magnet's North pole approaches the coil, magnetic flux within the coil increases. To counteract this rise, the coil must generate a magnetic field directed away from the magnet, causing the coil's near face to become a North pole. Like poles repel, resulting in a repulsive force between the coil and the magnet. This statement is valid.
(D) If the bar magnet does not move, there is no induced current in the coil.
Induced EMF necessitates a change in magnetic flux through the coil. A stationary magnet relative to the coil maintains a constant magnetic flux (\(d\Phi_B/dt = 0\)), thus preventing EMF induction and current flow. This statement is valid.

Step 3: Conclusion:
Statements (A), (C), and (D) are accurate, whereas statement (B) is inaccurate. Consequently, the correct selection encompasses only (A), (C), and (D).