Charged particles follow parabolic paths between parallel plates

Electric Fields & Potential — AQA A-Level Physics

A charged particle entering a uniform field perpendicular to the field lines experiences a constant force in one direction.
The result is a parabolic trajectory, identical in shape to projectileAn object moving freely under gravity after being launched. Horizontal and vertical components of motion are independent. motion under gravity.
A positive chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). is deflected towards the negative plate. A negative chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). towards the positive plate.
An uncharged particle (e.g. a neutron) passes straight through with no deflection.
Greater mass: less deflection.
Greater chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).: more deflection.
Greater speed: less deflection (spends less time between the plates).

Examiner Tips and Tricks

Less deflection means the particle hits the plate later and the path has a smaller curve.
Think of it as a heavier particle being harder to steer towards the plate.