Question

What should be the angle between thumb (main) finger, forefinger and central finger in Fleming's left hand rule? What does each finger indicate?

Answer 1

When a current carrying conductor is placed in an external magnetic field, a force acts on the conductor. Fleming's left hand rule is used to find the direction of that force. The thumb, forefinger and central finger of left hand must be mutually perpendicular (${90}^o$) to each other. The forefinger indicates the direction of external magnetic field, the central finger indicates the direction of current flowing in the conductor and the thumb points in the direction of force acting on the conductor.