--- 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: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # 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. The unit is volts per metre, which is the same as newtons per coulomb. **Example.** The energy change is Q times the voltage change, sign included. A positive charge moved to higher voltage gains potential energy; an electron moved to higher voltage loses it. An electron released from rest near the negative plate crosses a 200 V gap to the positive plate. Its potential energy falls by Q V = 1.6 times 10 to the minus 19 times 200 = 3.2 times 10 to the minus 17 J, and it gains that much kinetic energy. 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. Around a point charge Q the potential is V equals k Q over r, and it takes the sign of Q. **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 - [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) ## Optional connections - [Gravitational Potential and Escape Speed](https://lightmysky.com/learn/science/gravitational-potential-and-escape-speed-mt_drqTwCD9W8) ## 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)