Quick questions on Electric fields and potential: WACE Year 12 Physics Unit 3

Two oppositely charged parallel plates produce a uniform field (except near the edges). Its magnitude is

A charged particle entering a uniform field experiences a constant force, so its path is a parabola in exactly the same way a projectile is. The component along the field accelerates uniformly while the perpendicular component stays constant. This deflection of charges is the basis of cathode-ray tubes and is a favourite exam scenario.

WACE deliberately mirrors electric fields with gravitational fields so you can transfer reasoning. Gravitational field strength $g=GM/r^2$ is force per unit mass; electric field strength $E=kQ/r^2$ is force per unit charge. Both are inverse-square radial fields, both are vectors, and both give a constant uniform field in special geometries (near a planet's surface for gravity, between parallel plates for electricity). The decisive difference is that mass is single-signed so gravity only attracts, whereas charge has two signs so the electric field can point toward or away from a source and forces can repel.