The Electromagnetic & Strong Force (AQA A Level Physics): Revision Note

The electromagnetic force

• The electromagnetic force is only between charged particles

• The exchange particle that carries this force is the virtual photon, γ

• Properties of the photon are:

  • It has no mass

  • It has no charge

  • It is its own antiparticle

• Electromagnetic interactions occur whenever two charged particles interact with each other

• For example, when two charged particles, such as electrons, are repelled by each other, a virtual photon is exchanged between them to produce this repulsion

• The electromagnetic force is also responsible for binding electrons to atoms

  • This is due to the attractive force between the negative electrons and positive nucleus

Hadrons & the strong nuclear force

• Hadrons are particles that are made up of quarks

  • Hence they are subject to the strong interaction

• The exchange particle of the strong interaction is either:

  • the pion (between nucleons)

  • the gluon (between quarks)

• This means that leptons cannot interact with the strong force, since they are not made up of quarks