E/M for an Electron-Deflection of a Charge Moving in a Magnetic Field

Type of activity: demo

Activity code: M-010

Description:

Setup: 1. Connect as shown. 2. If the voltage in the Helmholtz is connected properly, the electron beam should be deflected outward from the opening. If not, the polarity of the Helmholtz coils must be reversed. To Operate: 1. Rotate resistor to change the current in the coils. 2. Observe the electron beam curl into a smaller circle as the coil voltage is increased (F = ev x B). 3. Increase the anode voltage. 4. Observe the electron beam expand outwards. Note: The filament of the electron gun should be turned on for 30 seconds or more before the anode voltage and should NEVER be turned off until the anode voltage is off. Otherwise, the tube will be damaged.