5H30.10 Cathode Ray Tube (Crookes Tube)
Electricity, force on moving charge, right hand rule
A beam of electrons is deflected by a magnet and/or charged plates.
-  Cathode ray tube (Crookes tube)
-  Crookes tube power supply or  Heathkit IP-32 power supply with (optional)  Xantrex XT 60-1 power supply
-  Banana cable
-  Bar magnet
-  Power bar with long cord
-  Camera (lecture hall document camera may work)
- Dim lights in order to make the electron beam more visible.
- Wire up the heater and accelerator contacts (and also deflector contacts, if desired) on the tube to the power supply (or supplies).
- If using the Heathkit supply, let it warm up by leaving it on standby for a few minutes.
- If using an external camera, position and focus it to see the tube end-on. Leave the camera on.
- Turn off automatic brightness adjustments on the camera, if applicable.
- Do not exceed 300 V on the accelerating voltage from the Heathkit power supply.
- A common error is to use the left-side knob on the Heathkit supply.
- Project the camera view to the class.
- Dim the lights.
- Turn on the power supply or supplies.
- Increase the accelerating voltage.
- Deflect electrons using magnet.
- (Optional) Deflect electrons with the deflector plates.
- When done, turn down all voltages.
- Turn off the power supply or supplies.
- The gas inside the tube is probably argon.
- We should probably not exceed 100 V on the deflecting plates. The Xantrex power supply is only rated to 60 V, so it should be fine.
- A more user-friendly power supply for this demo is available.
- The supplier for the cathode ray tube (Crookes tube in the catalogue) was Nada Scientific.
- The full-HD gooseneck camera works well with this demo.
- Magnetic force on a current-carrying wire
- CRT TV and magnets
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.