5H30.20 • Forces on Moving Charges: e/m Tube

Location: Floor Demo

Instructions / Notes:

• Turn on the emmitter power supply (2 switches). The unit will perform a 30-second self-test.
• Do not exceed 500 V and 2.0 A.
• The accelerating electric potential is set up with two 45V batteries.
• You should be able to see the electron beam if the lights are turned off.
• Turn on the coils' power supply that commend the intensity of the magnetic field between those coils. When varying the intensity of the magnetic field, the electron beam gets more or less curved.
• You may also hold a permanent magnet near to create a corkscrew path.

Demo Staff:

• This demonstration is stored as a floor demonstration with a black half-cylindrical cover.

Photos shows the apparatus used by the University of Texas at Austin.

Last updated on June 8, 2026