Question
Two bar magnets are moving rapidly towards a metallic loop joined across a capacitor C as shown in the figure. What is the polarity of the capacitor?
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Answer
Plane of the loop towards the north pole of the magnet (1) should act like a north pole and the plane towards south pole of magnet (2) should behave as a south pole so that as per Lenz's law induced currents in the loop can repel the motion of the magnets towards it.
On seeing from magnet (1) the direction of current in the loop should be from A to B (anticlockwise) and when seen from magnet (2), the direction of current flow will be clockwise. Hence, plate A of capacitor C will be at positive potential with respect to plate B. Hence plate A will be at positive potential and plate $B$ will be at negative potential.
On seeing from magnet (1) the direction of current in the loop should be from A to B (anticlockwise) and when seen from magnet (2), the direction of current flow will be clockwise. Hence, plate A of capacitor C will be at positive potential with respect to plate B. Hence plate A will be at positive potential and plate $B$ will be at negative potential.
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