Physics experiment. Pupil's hands using apparatus to demonstrate the electromagnetic Hall effect. The probe in the pupil's left hand is being held between the poles of a magnet (U-shaped object). The probe consists of an electric current-carrying conductor. The magnetic field exerts a force on the electrons making up the main electric current. This force makes the electrons drift and this is detected as a small electric current. Here a voltmeter (centre right) is being used to detect the Hall voltage of this induced current. The effect is strongest when the main current is aligned at right angles to the magnetic field. Rotating the probe causes the voltage to drop.