Fleming’s right-hand rule is a commonly used mnemonic in both physics and electrical engineering that shows the direction of the current generated in a conductor that is forcefully made to cut perpendicularly through a magnetic field. The force vector is perpendicular to the current and magnetic field vectors.
The rule can be applied for any of the three vectors, where knowing the direction of any two vectors enables the determination of the direction of the third vector. The right-hand rule is applied by holding the thumb, index finger and middle finger in mutually perpendicular directions. The direction of the thumb is commonly taken to be the force direction. The first finger points in the direction of the magnetic field, from north to south. The middle finger represents the direction of induced conventional current, from positive to negative.
“FBI” is a mnemonic that accompanies the right-hand rule, where F stands for force, B stands for magnetic flux, and I stands for current. The Fleming’s left-hand rule complements the right-hand rule, indicating the direction of the force induced in a conductor that has current flowing perpendicular to a magnetic field. The right-hand rule is commonly used in the design of electric generators, while the left-hand rule is used for electric motors.