---
title: "Electric Potential and the Uniform Field Between Plates"
description: "Between parallel plates the field is uniform and equals V over d, so a charge crossing the gap gains energy QV. Around a point charge the potential is kQ over r, and it takes the sign of the charge."
canonical: https://lightmysky.com/learn/science/electric-potential-and-the-uniform-field-between-plates-mt_LKTfeYxNde
source: https://lightmysky.com/learn/science/electric-potential-and-the-uniform-field-between-plates-mt_LKTfeYxNde.md
retrieved: 2026-09-12
---

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# Electric Potential and the Uniform Field Between Plates

Between parallel plates the field is uniform and equals V over d, so a charge crossing the gap gains energy QV. Around a point charge the potential is kQ over r, and it takes the sign of the charge.

Subject: Science · Area: Energy · Ages 16 to 18
Page: https://lightmysky.com/learn/science/electric-potential-and-the-uniform-field-between-plates-mt_LKTfeYxNde

## Ready when they can

- 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

## Lesson: Voltage between plates turns into energy

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.

**Example.** 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.

**Tip.** 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.

**Recap.** Plates turn voltage into uniform field, and crossing voltage turns into energy.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Gravitational Potential and Escape Speed](https://lightmysky.com/learn/science/gravitational-potential-and-escape-speed-mt_drqTwCD9W8)
- [Coulomb's Law and the Electric Field of a Point Charge](https://lightmysky.com/learn/science/coulombs-law-and-the-electric-field-of-a-point-charge-mt_p7FuzIsQch)

## Opens up

- [The Photoelectric Effect and the Work Function](https://lightmysky.com/learn/science/the-photoelectric-effect-and-the-work-function-mt_ADQK7WB2JN)
- [Calculating Electric Potential from a Charge Distribution](https://lightmysky.com/learn/science/calculating-electric-potential-from-a-charge-distribution-mt_B4WiVkpH4j)
- [Capacitance and the Energy Stored in a Capacitor](https://lightmysky.com/learn/science/capacitance-and-the-energy-stored-in-a-capacitor-mt_j1Eltr9z6l)
- [Photon Energy and the Electronvolt](https://lightmysky.com/learn/science/photon-energy-and-the-electronvolt-mt_UfmDhGRaYT)