This apparatus offers a clear and easy way to observe magnetic fields generated by a constant electrical current. A coil with 94 turns of 1 mm dia. copper wire is mounted on a base. Iron filings can be scattered on the clear plastic sheet which passes through the coil and when a current then flows around the coil, the magnetic lines of a force will be shown by the alignment of the filings. The apparatus can also be used in conjunction with a compass, magnetic field sensor or datalogger. Requires a high current laboratory power supply (5A or more) for best effect.