Chapter 9.3 - The Electron Gun

Question 1

What is an electron gun

Answer 1

Electrical device used to produce a narrow beam of electrons

Question 2

What is thermionic emission

Answer 2

The emission of electrons through the action of heat

Question 3

How does an electron gun work

Answer 3

• Small metal filament is heated by electric current

• Electrons in wire gain kinetic energy
-some gain enough to escape from metal’s surface

• If heated filament is in vacuum and high pd is applied between filament and anode
-filament acts as cathode

• Freed electrons accelerate towards anode
-gain kinetic energy

• If anode has small hole. Electrons in line with hole pass through it
-creates beam of electrons wirh specific kinetic energy

Question 4

Describe the energy transfer in an electron gun

Answer 4

• Electrons accelerate towards anode
-gain kinetic energy

• Work done on electron travelling from cathode to anode = eV

eV= 1/2mv^2