This sensitive balance has as adjustable counterweight and an optical lever for measuring tiny forces by the null method. It comes with a pair of straight aluminum rods for measuring the repulsive force between parallel current-carrying conductors and a pair of plates for measuring the attractive force between charged capacitor plates. A current of 10-20A is required to cause sufficient deflection in the electromagnetic experiment.

Fractional weights are then added to a small pan attached to the upper conductor rod to return the balance to its original position, determining the force between the conductors. The result may be interpreted to confirm the dynamic definition of the Ampere or to determine the permeability of air. The analogous electrostatic experiment may be used to find the permittivity of air.

From these two values, an indirect estimate of the speed of light may be made. Requires a lamp and scale for the optical lever, fractional weight set for the current experiment, precise multimeter to measure volts and amps, a 300V variable high voltage source and an AC or DC current source for 10-20A. Instructions for both experiments are included. Size of base: 30 x 36cm. The balance is also available without the capacitor accessory.

*Formerly Sargent-Welch brand WL2353C.*