Lorentz Force with a Cathode Ray Tube

PIRA 5H30.15

The cathode ray tube (crt) with an angled vertical phosphore-coated metal plate shown at left displays a visible "beam" of electrons. The beam is easily deflected with the magnetic field of a bar magnet. Ask students to predict the deflection for specific oreintations of a magnet.

The crt shown is an antique, and is irreplaceable, so be very, very careful.

The crt requires 10,000 V DC, which can be obtained from a veriable 12 V power supply connected to a DC transformer as shown. If no arc forms, adjust the spark gap between the contacts on the DC transformer. The contacts on the DC transformer often get oxidized to the point where an arc no longer forms. Gently sand both contacts if still no arc forms.