A single current-carrying loop of wire carrying current flows in the anticlockwise direction (seen from the direction) and lies in the plane. The plot of the component of magnetic field () at a distance (less than the radius of the coil) and on the plane vs coordinate looks like:
- A
Graph of vs : a flat-topped positive pulse, symmetric about , positive everywhere, decaying to zero on both sides.
- B
Graph of vs : two positive humps, one each side of , symmetric, dipping to zero exactly at .
- C
Graph of vs : an odd S-shaped curve — a negative trough for , zero at , a positive crest for , decaying to zero at large .
- D
Graph of vs : a single sharp positive peak centred at , symmetric, decaying to zero on both sides.