ICSE Class 10 Answered

It is found that whenever a current carrying conductor is placed inside a magnetic field, a force acts on the conductor, in a direction perpendicular to both the directions of the current and the magnetic field. To know the direction of force related to direction of current and direction of magnetic field, we use Flemings Left Hand rule as shown in left side figure below

Hold out your left hand with the forefinger, second finger and thumb at the right angle to one another. If the forefinger represents the direction of the field and the second finger represents that of the current, then thumb gives the direction of the force.

In the right side figure,  a portion of a conductor of length ‘L’ is placed vertically in a uniform horizontal magnetic field of strength ‘H’, produced by two magnetic poles N and S. If the current ‘I’ is flowing through this conductor, the magnitude of the force acting on the conductor is F = B×I×L . The direction of current , magnetic field and force is according to flemings left hand rule.