Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

The electron

Electrons were discovered by J J Thomson in 1897 – although he called them ‘corpuscles’. His discovery was based on experiments he and others had performed on cathode rays. 
Many of these experiments can be reproduced in the school physics laboratory. Not only are students seeing historic demonstrations, they are seeing the behaviour of an extraordinary and influential particle, a particle which: 

  • shows that atoms are not indivisible; 
  • is fundamental – a member of the lepton family – and is therefore thought to be indivisible itself; 
  • carries the basic unit of charge; 
  • is responsible for electrostatics (and takes its name from the Greek word for amber); 
  • is the carrier of electric currents in conductors; 
  • through its behaviour in vacuum tubes, led to the birth of electronic devices, the computer and cathode ray screens; 
  • through its behaviour in semiconductors, led to the birth of solid state electronics; 
  • was the first particle to be observed showing wave properties, leading to wave mechanics and quantum theory.