Module 4 - EPR (The Electron Gun) Flashcards
What is an electron Gun
An electrical device that produces a narrow beam of electrons
What are electron guns used for
- Oscilloscopes
- Electron microscopes
- Mass spectrometers
Describe the setup of the electron gun
- Cathode filament (often as a solenoid)
- And Positive Anode object with hole cut through the middle
- All in a vacuum
How is the filament made negative
It’s connected to the negative terminal
How is the anode made positive
It is connected to the positve terminal
What is a filament
A (non-ohmic) length of wire that current passes through causing it to heat up
Explain briefly how it works
- cathode filament and anode repel and attract the electrons in the wire respectively
- A current is passed through the cathode which due to the filament resistance, causes the ehating effect
- Some electrons gain enough Ek from the heating of the wire to free themselves from the cathode escaping the surface of the metal by thermionic emission
Why is there a hole in the cathode
The hole is used to concentrate the beam of electrons that escape the cathode
What is thermionic emission
the release of electron sthrough the transfer of thermal energy to metals
Why is this system placed in a vacuum
The air is too dense for electrons to pass through so a vacuum alows electrons to pass.
What is the accelerating pd
The idea that the huge difference in pd between the cathode and the anode causes the electrons to accelerate
What is the equation for the energy transfers as the electrons move from cathode to anode
eV =0.5mv^2
