Electric field strength (A-level only)

Magnitude of $E$ in a uniform field given by $E = \frac{V}{d}$

Derivation from work done moving charge between plates: $Fd = Q\Delta V$

Trajectory of moving charged particle entering a uniform electric field initially at right angles.

Magnitude of $E$ in a radial field given by $E = \frac{1}{4\pi\varepsilon_0}\frac{Q}{r^2}$