# Charge and Current

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Conventional Current
A model used to describe electric current in a circuit - conventional current travels from positive to negative - it is the direction in which positive charges would flow.
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Charge Carrier
A particle with charge that moves through a material to form an electric current. For example, an electron in a metal wire.
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Coulomb
The derived SI unit of electrical charge C. 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere. 1C=1As
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Ampere
The base SI unit of electric current, symbol A, defined as the current flowing in two parallel wires in a vacuum 1 metre apart such that there is an attractive force of 2.0x10^-7 Newtons per metre length of wire between them.
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Electric Charge
A physical property, symbol q or Q, either a positive or negative measured in coulombs, C or as a relative charge.
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Electric Current
The rate of flow of charge, symbol I, measured in amperes A. Normally a flow of electrons in metals or a flow of ions in electrolyte.
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Elementary Charge
The electric charge equivalent to the charge on a proton, 1.6x10^-19 C, symbol e.
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Electrolyte
A liquid containing ions that are free to move and so to conduct electricity.
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Anion
A negatively charged ion, one which is attracted to an anode.
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Cation
A positively charged ion, one which is attracted to a cathode.
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Conservation of Charge
A conservation law which states that electric charge can neither be created, nor destroyed. The total charge in any interaction must be the same before and after the interaction.
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Kirchhoff's First Law
At any point in an electrical circuit, the sum of the currents into that point is equal to the sum of currents out of that point. Electrical charge is conserved.
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Semiconductor
A material with a lower number density than a typical conductor, e.g. silicon.
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Number Density
The number of free electrons per cubic metre of a material, symbol n, unit m^-3.
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Mean Drift Velocity
The average velocity of electrons as they move through a wire in ms^-1.
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## Other cards in this set

### Card 2

#### Front

A particle with charge that moves through a material to form an electric current. For example, an electron in a metal wire.

Charge Carrier

### Card 3

#### Front

The derived SI unit of electrical charge C. 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere. 1C=1As

#### Back ### Card 4

#### Front

The base SI unit of electric current, symbol A, defined as the current flowing in two parallel wires in a vacuum 1 metre apart such that there is an attractive force of 2.0x10^-7 Newtons per metre length of wire between them.

#### Back ### Card 5

#### Front

A physical property, symbol q or Q, either a positive or negative measured in coulombs, C or as a relative charge.

#### Back 