The Left-Hand Rule and Right-Hand Rule developed by John Ambrose Fleming are commonly used to show the direction of motion, current, and magnetic field in electric motors or generators, as well as applicable in magnetism and electromagnetism.
Right-hand Rule For Generators
According to electromagnetic induction, when a conductor moves through a magnetic field, an electric current is induced. The right-hand rule is used to determine the direction of the induced current.
As you can see in the following picture, arrange your thumb, forefinger, and middle finger of your right-hand perpendicular to each other. The direction the thumb points to is the motion of the conductor through the magnetic field, the direction the forefinger points to is that of the magnetic field, and the direction the middle finger points to is that of the induced current.
This picture is another one of the right-hand rule. Make your thumb perpendicular to your forefinger with the palm facing the director of the magnetic field. The thumb points towards the direction of the conductor motion and the remaining four fingers point towards the direction of the induced current.
Left-hand Rule for Electric Motors
When a current-carrying conductor is put in a magnetic field, the conductor will produce a force perpendicular to both the field and the current flow’s direction. The left-hand rule is used to find the direction of the generated force.
As you can see in the following picture, arrange your thumb, forefinger, and middle finger of your left hand perpendicular to each other. The direction the thumb points to is that of the force, the direction the forefinger points to is that of the magnetic field, and the direction the middle finger points to is that of the electric current.
Conclusion
The left-hand rule is applied in electric motors and the right-hand rule in generators. In practice, these rules are never used except as a convenient trick to determine the direction of the resultant – either current or thrust.