A pair of preformed coils, each with 400 turns of copper wire, wound onto a former of approx. 150 mm diameter. Each coil is mounted on a support rod, which fits onto the sliders of the track system supplied. This enables the distance between the coils to be varied whilst maintaining alignment along a common axis, for measurements and study of magnetic fields. Electrical connection is via 4 mm sockets. Please note: the current should not exceed 1A, to prevent overheating or damage.