Question: What is the force that a conductor of length L carrying a current I experiences when placed in a magnetic field B? What is the direction of this force?

### Force on a current carrying conductor

When current passes through a conductor, a magnetic field is produced around it. When a current carrying conductor is placed between the poles of a permanent magnet, the two magnetic fields interact with one another. Therefore, the conductor experiences a force due to the interaction of these fields. It has been found that the magnitude of this force varies directly with the current I flowing in it, length of the conductor in the field, strength of the external permanent magnet and the sine value of the angle between the length of the conductor and the magnetic field. Therefore,

F = IBLsinθ

Obviously, the force would be maximum for θ = 90o and minimum for θ = 0o.

Direction of the force

The force is vector product of length L and magnetic field B and hence will be perpendicular to the plane of L and B. The exact direction of the force is determined by the use of Fleming’s Left Hand Rule.