Relative motion between closed loop and magnet
Move a magnet to the closed loop quickly, and the pointer of the galvanometer connected to both ends of the coil will deflect, indicating that there is a current passing through the closed loop, which is called an induced current. When the magnet stops moving, the needle of the galvanometer is zero, i.e. there is no current in the loop. When the magnet is moved out of the closed loop, the pointer of the galvanometer is deflected again, but the deflection direction is opposite to the direction when it was moved in, indicating that a current is generated in the closed loop, but the direction is changed.
If the magnet does not move, moving the loop rapidly towards the magnet, or moving the loop away from the magnet, will produce similar results. In short, as long as there is relative motion between the magnet and the closed loop, an induced current is generated in the closed loop.
