The direction of a magnetic field relative to the direction of current flows can be determined by “Ampere’s Rule”. This “Rule” can be dramatically demonstrated using this apparatus. It is connected to a 5 VDC power supply and positioned so that the horizontal rod is pointing roughly north and south. The included six miniature compasses are arranged in a circle around the vertical rod. When the power supply is turned on, a major change in the direction of the compass needles is seen. The same result will be seen using the larger compass.