A bar magnet with its south pole down passes through a conducting ring. As viewed from above the ring, in which direction does the current flow?
(a) cw
(b) ccw
(c) no current flows
To determine the direction of the current flow in the conducting ring when a bar magnet passes through it, you can use the right-hand rule for electromagnetism. This rule states that if you point your thumb in the direction of the magnetic field and curl your fingers, the direction of the current will be the direction in which your fingers curl.
In this scenario, the magnetic field produced by the bar magnet is directed from the south pole to the north pole. So, when the south pole of the bar magnet is pointing down through the conducting ring, the magnetic field lines will be pointing upwards through the ring.
Now, if you place your right hand above the ring and curl your fingers in the direction of the magnetic field lines (which are pointing upward), your thumb will point in the direction of the current flow.
By following this procedure, you will find that the current flows in the counterclockwise direction (ccw) as viewed from above the ring. Therefore, the answer is (b) ccw.