The field due to a wire of n turns and radius r which carries a current I is measure on the axis of the coil at a small distance h form the centre of the coil. This is smaller than the field at the centre by the fraction:

The magnetic field normal to the plane of a coil of N turns and radius r which carries a current I is measured on the axis of the coil at a distance h from the centre of the coil. This is smaller than the field at the centre by ther fraction.

The field normal to the plane of a wire of n turns and radis r which carriers i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the field at the centre by the fraction.

The field normal to the plane of a wire of n turns and radis r which carriers i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the field at the centre by the fraction.

The field normal to the plane of a wire of n turns and radis r which carriers i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the field at the centre by the fraction.

The field normal to the plane of a wire of 15 turns and radius r which carries 1 A is measured on the axis of the coil at a small distance d from the centre of the coil. This is smaller than the field at the centre by the fraction

The field normal to the plane of a wire of 15 turns and radius r which carries 1 A is measured on the axis of the coil at a small distance d from the centre of the coil. This is smaller than the field at the centre by the fraction

A circular coil of n turns and radius r carries a current I. The magnetic field at the centre is