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Introduction
Capacitance
Incomplete capacitor circuits
Charge flow
Storing charge
Stored charge: effect of voltage
Capacitance formula
Stored charge: other factors
Designing capacitors (1)
Designing capacitors (2)
Energy stored in a capacitor
How much energy is stored?
Stored energy: graphical view
Charging through a resistor
Analysing the charging data
Discharging a capacitor
Analysing capacitor discharge
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By Jeff Preston, Newton-le-Willows Community High School
Paul Berry, MATTER Project
A capacitor is an electronic component which is used in a wide variety of
circuit applications due to its ability to store charge.
Learning outcomes
After completing this section, you should be able to:
 | provide a definition of capacitance and name its units; |
| explain how a capacitor can be produced to give a particular value of capacitance.
To do this, you will need to:
 | recall and use an equation which relates capacitance to charge (Q) and voltage (V); |
| recall and use an equation which relates capacitance to the plate separation (d), area (A)
and dielectric permittivity (e); |
| describe briefly what is meant by the term permittivity and state its units; |
| explain that permittivity is a material property; |
| explain the term relative permittivity, er, and state its units; |
| explain why e = e0er; |
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| explain why a capacitor has a maximum working voltage; |
| determine experimentally the energy stored in a capacitor; |
| explain the terms "half-life" and "time constant" as applied to
capacitor circuits; and |
| determine experimentally the "half-life" and "time constant" of a
capacitor/resistor circuit. |
Assumed prior knowledge
It is assumed that you have knowledge of the following concepts:
| basic electrical terms such as voltage, current and charge. |
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