# Physics revision-Electricity

As Physics

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• Created by: Courtney
• Created on: 26-10-11 10:45

## Current and Charge

Current is the rate of flow of charge.

Charge is energy stored chemically, for conversion into electricity.

-Current is measured in Amps.

-Charge is measured in Coulombs.

-The formula relating current and charge is I = delta Q / delta T

-In a metal, electrons are the charge carriers. Their charge is 1.602 x 10 -19

-As well as electrons, ions in fluids can also be the charge carriers.

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## Formulae

The formula relating current, time and charge = I = delta Q / delta T

The formula relating power, current and p.d = P = I x V

The formula relating resistance, current and p.d = R = V / I

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## Potential Difference

Potential Difference is the energy provided or used per unit charge.

-Potential difference is measured in volts.

-The voltage supplied to a circuit by a power pack/cell is called EMF (electric motive force).

-The total EMF is equal to the total P.D

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## Power

-Formula for power is P = I x V

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## Resistance

Resistance is a materials opposition to the flow of electric current.

-Resistance is measured in Ohms.

-The formula for resistance is R = V / I. This is Ohms law, it implies that resistance is constant for a particular material.

-Factors that effect resistance include temperature,

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## Resistivity

Resistivity is to do with the resistance of a certain material.

The unit of Resistivity is

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