Reference: EM152
Category: Electromagnetism
Purpose: Shows the force on a moving charge in a magnetic field.
Description: a) Unshielded cathode-ray oscilloscope. A spot on the screen shows where the electron beam strikes it. Bring a bar magnet near the tube, either from above or from one side, and show that the beam is deflected transversely. Bring the bar from directly in front of screen and no deflection occurs.
b) Cathode-ray tube in which the electron beam casts the shadow of a Maltese cross on the fluorescent screen. A high voltage power supply is required to give the screen its fluorescence. The light from the filament also casts a shadow. Approach with a bar magnet form the side or from above, and show that the electron shadow is deflected transversely while the light shadow is unaffected. Approach from the front (along the axis of the tube) and show that, while the shadow is not affected laterally, it does however rotate.
