This kit includes an air core solenoid and a current balance for demonstrating and measuring the small force experienced by a conductor carrying an electric current in a magnetic field. To run the experiment, one half of the current balance is placed inside the solenoid. The other half has an adjustable counterweight and can carry light additional masses. When current is supplied to the balance and 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. Includes activity guide.