The behaviour of protons, neutrons and electrons in electric fields

The behaviour of protons, neutrons and electrons in electric fields

What happens if a beam of each of these particles is passed between two electrically charged plates - one positive and one negative? Opposites will attract.

Protons are positively charged and so would be deflected on a curving path towards the negative plate.

Electrons are negatively charged and so would be deflected on a curving path towards the positive plate.

Neutrons don't have a charge, and so would continue on in a straight line.

Exactly what happens depends on whether the beams of particles enter the electric field with the various particles having the same speeds or the same energies

If the particles have the same energy

If beams of the three sorts of particles, all with the same energy, are passed between two electrically charged plates:

• Protons are deflected on a curved path towards the negative plate.
• Electrons are deflected on a curved path towards the positive plate.

The amount of deflection is exactly the same in the electron beam as the proton beam if the energies are the same - but, of course, it is in the opposite direction.

• Neutrons continue in a straight line.

If the electric field was strong enough, then the electron and proton beams might curve enough to hit their respective plates.

If the particles have the same speeds

If beams of the three sorts of particles, all with the same speed, are passed between two electrically charged plates:

• Protons are deflected on a curved path towards the negative plate.
• Electrons are deflected on a curved path towards the positive plate.

If the electrons and protons are travelling with the same speed, then the lighter electrons are deflected far more strongly than the heavier protons.

• Neutrons continue in a straight line.

 

Protons, neutrons and electrons.

	relative mass	relative charge
proton	1	+1
neutron	1	0
electron	1/1836	-1