Illustration of Lenz's law, which states that the direction of an induced current is such that it opposes the change producing it. A bar magnet moved towards a solenoid induces a current in the solenoid coil (top image). The direction of this current creates a magnetic field which repels the bar magnet. A bar magnet moved away from the solenoid induces a current in the opposite direction, creating a magnetic field which attracts the bar magnet (bottom image).