The classic method for demonstrating and measuring the small force experienced by a conductor carrying an electric current in a magnetic field. One half of the balance is placed inside a solenoid (like United Scientific model ACS001). The other half has an adjustable counterweight and can carry light additional masses. When current is supplied to the balance and the solenoid from an external power supply, the balance deflects. Adding light masses until balance is restored allows the force on the conductor to be measured.