A conducting circular rigid loop near a long straight current carrying wire is shown. Match the following table :
| Column I | Column II |
| (A) If current is increased | (P) Induced current in the loop is clockwise |
| (B) If current is decreased | (Q) Induced current in the loop is anticlockwise |
| (C) If loop is moved away from the wire maintaining constant current in the straight wire. | (R) Wire will attract the loop and there will be no torque about y–axis |
| (S) Wire will repel the loop and there will be no torque about y–axis |
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This involves Faraday's law and Lenz's law. The magnetic field from the straight wire is into the page on the loop's side, given by . To oppose any change in flux:
(A) If current I increases, flux into page increases. Induced current creates field out of page: anticlockwise (Q).
(B) If I decreases, flux into page decreases. Induced current creates field into page: clockwise (P).
(C) Moving loop away decreases flux into page. Induced current is clockwise (P) to oppose this decrease. The force between the wire and this clockwise current loop is attractive (R), with no net torque.
Final Answer: (A)→(Q), (B)→(P), (C)→(P) and (R)