The moving electron creates a magnetic field around its path. As the electron approaches the coil, the magnetic flux through the coil increases. According to Lenz's Law, an induced current is generated to oppose this increase . As the electron passes the coil and moves away, the magnetic flux through the coil decreases. Again, by Lenz's Law, the induced current flows in a direction to oppose this decrease (i.e., it tries to maintain the flux).

This behavior is analogous to the experiment described in the text where a magnet is pushed towards and then pulled away from a coil, causing the galvanometer deflection to reverse . Since the nature of the flux change switches from 'increasing' to 'decreasing', the direction of the induced current must reverse.