What is neutral point in a magnetic field ?

What is a neutral point in a magnetic field of a bar magnet.

Earth's magnetic field is 5xx10^-5 T. A cable is 10 m above the ground. Calculate the current in the cable, so that it may produce a neutral point with earths' magnetic field on the surface of the earth just below it.

A long straight horizontal cable carries a current of 2.5 A in the direction 10^@ south of west to 10^@ north of east. The magnetic meridian of the place happens to be 10^@ west of the geographic meridian. The earth’s magnetic field at the location is 0.33 G, and the angle of dip is zero. Locate the line of neutral points (ignore the thickness of the cable)? (At neutral points, magnetic field due to a current-carrying cable is equal and opposite to the horizontal component of earth’s magnetic field.)

What is radial magnetic field ?

What is the work done by a magnetic field on a moving charge?