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Resistance

The electrical resistance of a component is a measure of its opposition to the flow of electric current through it.Electrical resistance is the ratio of the potential difference across the component to the current flowing through that component.
resistance=p.d. across component
current through component
R=V
I
ohms=volts
amps
The SI unit for resistance is the ohm (Ω).The resistance of an object partly depends on the material it is made of. Objects made of electrical insulators have very high resistance, while objects made of electrical conductors like metals have very low resistance. The nature of a material is not the only factor in resistance.All objects resist electrical current, except for superconductors, which have a resistance of zero.

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Specification: AQA Physics (7407), AS-level, 3.5.1.3 Resistivity and 3.5.1.1 Basics of electricity. Topic: Electric Current.

Key terms in this lesson

Electromotive force
The electrical energy produced per unit charge by a source, such as a cell, in driving current around a circuit.
Potential difference
The energy transferred per unit charge as charge moves between two points in a circuit.
Resistance
The ratio of the potential difference across a component to the current flowing through it, measured in ohms.

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