What a learner can do afterwards
- Uses E = V over d for the field between plates and states the unit volts per metre
- Calculates the work done moving a charge through a potential difference as QV
- Sketches equipotentials for plates and for a point charge and says how they meet the field lines
1 · Read
Two parallel plates with a voltage across them make a uniform field. Its strength is E equals V over d, with d in metres, in volts per metre.
An electron crossing a 500 V gap gains energy equal to Q V, then spends it as speed. A positive charge moved the same way gains the opposite way round, since its sign is opposite.
An equipotential joins points at one voltage, and moving along it takes no work. Equipotentials always meet field lines at right angles, for plates and point charges alike.
Volts per metre is identical to newtons per coulomb, so either unit fits E. Watch the sign: a negative charge moved to higher voltage loses potential energy.
Plates turn voltage into uniform field, and crossing voltage turns into energy.
2 · Watch
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Where it sits
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Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.