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Components of a circuit that build up charge.

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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)

Illustration of the distribution of charge in insulators and conductors

License: CC BY-NC 3.0


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.

Illustration of a charged object being grounded

License: CC BY-NC 3.0


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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