1.1.5—Behaviour of beams of protons, neutrons

In an electric field, a charged particle experiences a force toward the oppositely charged plate; a neutral particle is not deflected by this electric force. Comparing beams at the same speed reveals how charge and mass affect the deflection.

A proton has relative charge +1 and relative mass 1, so it bends toward the negative plate. An electron has charge −1 and a much smaller mass, so it bends toward the positive plate and is deflected more strongly. A neutron has zero charge and continues undeflected in the electric field.

The direction of deflection identifies the sign of charge, while the amount of bending depends on the force relative to the particle’s mass. The electron’s very small mass gives it a much larger acceleration than a proton in the same field.

The comparison assumes beams with the same speed and a stated electric-field arrangement. Do not infer particle identity from deflection alone without checking the field direction and the experimental conditions; magnetic-field details are not added beyond the supported objective evidence.