Also called Current balance. For demonstration of the relationship between force acting on a current carrying a conductor in a magnetic field. Two metal pillars mounted on an insulated base, each with a 4mm hole for electrical connecting. Conducting arms, consisting of a metal wire shaped into a rectangular L-loop, are mounted on a balance beam, which is supported on the pillar by two conical bearings that act as fulcrum. Two screwed masses are attached to the beam, one horizontally, for adjusting the equilibrium position of the arms, and the other vertically for adjusting the sensitivity. One conducting arm current a rider, which adjust equilibrium with the current flowing by sliding along a scale graduated 0-75 X 1mm. the bend at the end of the conducting arms oscillators vertically in the magnetic field produced by a compound magnet, comprising five identical, horseshoe magnets mounted in the frame. The magnets can slide along a rod mounted on the base with a 6cm scale, giving the length of arms in the magnetic field.