The GENERATOR EFFECT is when an electrical CONDUCTOR (such as a wire) INDUCES (creates) a POTENTIAL DIFFERENCE across when it either:

• MOVES relative to a MAGNETIC FIELD or
• Experiences a CHANGE IN MAGNETIC FIELD. 

If the conductor is part of a COMPLETE CIRCUIT, it ALSO induces a CURRENT in the conductor. 

You can think of the GENERATOR EFFECT as the OPPOSITE of the MOTOR EFFECT.

Examples of the generator effect are:

Moving a wire THROUGH a magnetic field:

Moving MAGNETS through a SOLENOID so that the wire experiences a CHANGE in magnetic field:

If the generator effect occurs in a COMPLETE CIRCUIT and a CURRENT is induced, the CURRENT created OPPOSES the original change that created it. 

eg. If you move a wire DOWNWARDS through a magnetic field to induce a POTENTIAL DIFFERENCE and CURRENT, the wire would experience a force UPWARDS to OPPOSE the downwards motion.

The POTENTIAL DIFFERENCE induced can be increased by:

• INCREASING the SPEED of the motion of the magnet or conductor.
• INCREASING the STRENGTH of the MAGNET.
• INCREASING the NUMBER OF TURNS in the SOLENOID.

The DIRECTION of the current induced can REVERSED by:

• MOVING the wire or conductor in the OPPOSITE DIRECTION.
• SWITCHING the orientation of the POLES on the magnet.