When a current carrying wire is placed in a magnetic field, a force is exerted on the wire. Fleming gave a simple rule to determine the direction of force acting on a current carrying wire placed in a magnetic field.
According to Fleming's left-hand rule, hold the fore finger, the centre finger and thumb of your left hand at right angles to one another.
Adjust your hand in such away that the fore finger points in the direction of magnetic field and the centre finger points in the direction of current, then the direction in which the thumb points, gives the direction of force acting on the conductor.
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| Fleming's Left-hand Rule |
Note:-
- Fleming left-hand rule suitable in electric motor.
- With the help of Fleming rule, we find the direction of force acting on the rotor.
- In permanent magnet, stator field is known from N⟶S. But in temporary or electromagnet, field is not fixed, it changes relative to rotor rotation.