# Charge and Current

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• Created on: 04-04-17 11:30
Electric Current
The rate of flow of charge.
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Electric charge
Physical property, Q either positive or negative measured in Coulombs.
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Coulombs
Unit of electical charge, 1 coulomb of charge passes a point in one second where there is a current of 1 amp.
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Amperes
1 amp is one coulomb per second.
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Elementary charge
The charge on a proton, 1.6x10-19C
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Conventional current
Movement of current from positive to negative (the direction the positive charges would travel).
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Resistance
Property of a material calculated by dividing potential difference by current, measured in ohms.
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Conservation of charge
Electric charge cannot be created or destroyed - the total charge in any interaction must be the same before and after.
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Kirchhoff's 1st Law
At any point in an electrical circuit, the sum of currents into a point is equal to the sum of currents out of that point, charge is conserved.
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Number density
The number of free electrons per cubic metre of material (m-3).
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Semiconductors
A material with a lower number density than a conductor.
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Mean drift velocity
The average velocity of electrons as they move through a wire (ms-1).
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## Other cards in this set

### Card 2

#### Front

Physical property, Q either positive or negative measured in Coulombs.

Electric charge

### Card 3

#### Front

Unit of electical charge, 1 coulomb of charge passes a point in one second where there is a current of 1 amp.

#### Back ### Card 4

#### Front

1 amp is one coulomb per second.

#### Back ### Card 5

#### Front

The charge on a proton, 1.6x10-19C

#### Back 