Whenever a current carrying conductor is placed in a uniform magnetic field. It will experience a magnetic force. However, the magnetic force depends on various parameters. Hence the magnetic force depends on four things:

•Amount of current

•Strength of Magnetic field

•Length of the wire which remain in magnetic field

•And the angle between the current carrying conductor and magnetic field.

The most important criteria here is the angle between the current carrying conductor and the magnetic field. If the angle is 0° or 180° then there will be no force acting on the wire. But if the angle is 90° the force will be maximum. If you observe the pattern it goes on like that, at 0° the force is 0 but as the angle increases the force increases and at 90° the force reaches its maximum value. And then again it starts decreasing and it becomes 0 at 180°. Hence,

(a) parallel to magnetic field

When the current carrying wire is placed parallel or anti-parallel to the magnetic field the magnetic field does not act on it.

(b) perpendicular to magnetic field

When the current carrying conductor is placed perpendicular to the magnetic field then magnetic force acting on conductor is maximum.