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Parallel-plate capacitor
Beginner
Capacitance depends on area and gap.
C = ε₀A/dC = ε₀A/d for plate area A and gap d. Increasing area or decreasing gap increases capacitance.
A = 0.01 m², d = 1 mm: 88.5 pF.
Valid when d is small compared with plate size.
In more detail
For a parallel-plate capacitor, C = ε0A/d, where A is the plate area and d is the separation. Capacitance increases with area and decreases with separation.
Real-world uses
- Touch sensors measure capacitance changes caused by a finger.
- Tuning circuits use variable parallel-plate capacitors.
- Engineers design touch screens and microphones using parallel-plate capacitors whose capacitance changes with position or pressure.
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Frequently asked questions
How can I increase capacitance?
Use larger plates, bring them closer, or add a dielectric.
Is the field uniform?
Approximately, between large plates and away from the edges.
How can I make a capacitor store more charge?
Use larger plates, put them closer together, or use a material with a higher permittivity between them.
Related topics in Electrostatics
Electron volt · Potential energy of charges · Capacitor · Capacitors in series · Capacitors in parallel · Energy in a capacitor