1. The Electron Gun Learning Objective:
Describe thermionic emission Explain the process of an electron gun State the factors which affect the deflection of an electron beam

2. Write down everything you know about..
ELECTRONS

3. As the _________ increases, thermionic _______ occurs
As the _________ increases, thermionic _______ occurs. An atom changes into an ___ emitting an _________.

4. Defining Words Thermionic emission.
Therm- is a prefix relating to heat.
Emission means
giving out.
-ionic is referring to ions, or charged particles, in this case an electron.

5. Can you label the parts of the gun?
Electron gun
cathode
grid
anodes
y-plates
x-plates
fluorescent screen
Heated by 6V supply.
Greater voltage of 4000V, ACCELERATES electrons to high speeds.
Can you label the parts of the gun?

6. Operation
The electrons are first ‘evaporated’ from a hot cathode (negative electrode) - similar to the tungsten filament in a low-voltage light bulb (thermionic emission)
The resulting cloud of electrons is attracted towards a high-voltage anode (positive electrode)
A hole at the end of the anode allows a proportion of the rapidly moving electrons to ‘shoot’ through, producing an electron beam
Once created by the gun, the electron beam proceeds through a vacuum inside the tube until it collides with a fluorescent screen.
Here, energy from the electron beam is released in the form of light, indicating the presence of the beam

7. How does it work?
Electrons strike the fluorescent screen and seen as a spot of light
The electrons are attracted to the anodes and accelerated
Electron beam passes through the X and Y plates
Hot metal filament emits electrons

8. Uses of electron beams? Oscilloscopes TV tubes Electroplating
X ray production
Monitors
Combustion engines

9. Questions In an electron gun explain why: a the cathode is heated
b the electrons accelerate from the cathode to the anode
c there is a hole in the anode
d there is a vacuum in the container.