The IEC Current Balance Kit is designed to fit directly to the IEC Air Cored Solenoid.
It consists of a platform that is simply attached to the end cheek of the solenoid and a slim blade carrying one single turn of conductor which balances in sensitive pivots on the two small round support rods fitted to the platform.
When current is passed through both the solenoid coil and the single turn, the blade deflects due to the interaction of the magnetic fields. Small weights are added to the beam to restore the balance and the weight required is a measurement of the force on a conductor carrying current whilst inside a magnetic field.
This is the theory that causes electric motors to turn.