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Capacitors
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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

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;
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.
 

Materials Teaching Educational Resources
1999 MATTER Project, The University of Liverpool

ESF flagSupported by the European Social Fund under
the Objective One programme for Merseyside