Lenz's law
Lenz's rule states that an electric current caused by an induction voltage is always directed in such a way that it counteracts the cause of the induction.
If a conductor is moved in a magnetic field, a voltage is induced in the conductor, which results in a current. This current causes a magnetic field in the conductor, which is superimposed on the pole field. This field is directed in such a way that the common field in front of the conductor is compressed and therefore exerts a force on the conductor which is opposite to the movement. According to the generator rule, the direction of the current can be determined from the direction of the field line congestion.
The generator rule states that if you hold your right hand so that the field lines meet the inner surface of the hand from the north pole, and the splayed thumb points in the direction of motion, the induction current will flow in the direction of the outstretched fingers.