# Capacitors

## Components of a circuit that build up charge.

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Capacitors

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#### Sharing Charge

Recall that insulators are materials that don't let electrons flow easily, whereas conductors allow electrons to flow through them freely. What happens to excess electrons on a conductor? On an insulator? (Hint: use the image below to help you explain)

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[Figure1]

If you touch a charged conductor to an uncharged one, the combination becomes one big, charged conductor. What happens to the charge?

The earth is also a conductor! Touching a charged object to the earth is called grounding.

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[Figure2]

What happens when you touch a conductor to the earth, and why? Why are many electrical devices, such as most household appliances, grounded?

Remember: spheres always have excess charge on the surface, as explained by Gauss's Law.

#### Capacitors Store Charge

Capacitors store an electric charge and can be used to smooth out electrical impulses or to turn constant electric currents into a series of impulses.

Most capacitors consist of parallel plates of area (A) separated by a distance (d) with an insulator in between the plates. What happens if voltage is applied to the capacitor?

For a given capacitor, you can define the relationship among the charge, capacitance, and voltage with the formula Q = CV.

What is capacitance?

Remember: the SI unit for capacitance is a farad (F), which is the equivalent of a coulomb/volt.

You can check your answers and find more information about capacitors here.

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