Why and whe

The drifting of electrons in the a conductor in a definite direction causes the current to flow through it, When such conductor is placed in an uniform magnetic field, each drifted electron of a conductor experience a magnetic force. This force collectively experience by a conductor as whole . Hence a current carrying conductor in magnetic field experience a force when kept in external magnetic field.

The direction depends upon:

1) Direction of current through the conductor, and

2) Direction of magnetic field.