When the magnet passes through the coil at a constant speed to the right, the N-pole is close to the coil, the induced current in the coil always impedes the relative motion of the magnetic poles, giving the poles a force to the left, then the magnetic poles give the coil a force to the right, the coil is stationary because of the friction force to the left. When the N pole leaves the coil, the induced current in the coil always hinders the relative motion of the poles, giving the poles a force to the left, then the poles give the coil a force to the right, and the coil is stationary because of the friction force to the left. So the friction force on the coil is always to the left. Therefore, A is correct, B is wrong.
CD, when the original magnetic flux increases, the magnetic field of the induced current and the original magnetic field in the opposite direction; when the original magnetic flux decreases, the magnetic field of the induced current and the original magnetic field in the same direction. When the magnet N pole to the right near the coil, the coil upward magnetic field increases, the magnetic field of the induced current downward, so the induced current clockwise. When the N-pole of the magnet moves away from the coil to the right, the magnetic field in the coil decreases and the magnetic field of the induced current goes up, so the induced current goes counterclockwise. when the S-pole is close to the coil, the magnetic field increases and the magnetic field of the induced current goes up, so the induced current goes counterclockwise. when the S-pole moves away from the coil, the magnetic field decreases and the magnetic field of the induced current goes down, so the induced current goes clockwise. Therefore, C is correct, D is wrong.
The choice: AC
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