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How an electron gun works

The electrons come from a hot piece of metal

A metal element is heated by a low voltage and electrons ‘boil’ off the surface.

Try Why Do Astronauts Float by Julian Hamm

Electron guns work by repulsion not attraction

If you give the element a very high negative voltage then the electrons are repelled and accelerate away.  The ‘anode’ is like a metal can with a hole in it.  The electrons pass through the hole and come out as a beam.

The anode is earthed.  This means it is at zero volts so there is no tendency for the electrons to be attracted back to it.

You can’t see the electrons themselves but they make the very low pressure gas in the tube glow green so you can see where they go.

back to Lesson 8: Atoms 2: Electrons