Capacitor

Beginner

Device storing charge and energy.

Key relationC = Q/V

Two conductors separated by an insulator store charge ±Q; the capacitance C = Q/V is the charge stored per volt, measured in farads.

Worked example

A 100 μF capacitor at 12 V holds 1.2 mC.

Common mistake

Typical capacitors are μF to pF.

In more detail

A capacitor stores electric charge and energy between two conductors separated by an insulator. Its capacitance C = Q/V is measured in farads.

Camera flashes use capacitors to release energy quickly.
Capacitors smooth the voltage in power supplies.
A camera flash uses a capacitor to store charge and release it quickly to produce a bright light.

What is a farad?

One coulomb per volt, a very large unit, so microfarads and picofarads are more common.

Does a capacitor hold charge permanently?

No, it can discharge through leakage paths.

What does a capacitor do?

It stores charge and energy in an electric field between two conductors separated by an insulator.