Defined as the current flowing in two parallel wires in a vacuum 1m apart such that there is an attractive force of 2 x 10 -7 N per metre length of wire between them
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Positive
One type of electric charge, attract negative repel other positives
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Negative
A type of electric charge such that it repels other negative charge and attracts positive charge.
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Coulomb (C)
The derived SI unit of electric charge.
1 coulomb of electric charge passes a point each second when there is a current of one amp
1 coulomb = 1 amp x second
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Electric Charge
Physical property (symbol of q or Q)
Positive or negative
Measured in coulombs or as a relative charge
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Ion
An atom that has either lost or gained electrons
Has a net charge
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Relative Charge
A simplified measurement of the electric charge of a particle or object
Measured in multiples of the elementary charge (q or e)
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Quantise
The availabilty of some quantities only in certain discrete values
Examples are elementary charge
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Conventional Current
A model used to describe electric current in a circuit
Travels from positive to negative
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Free Electrons
An electron in a metal that is not bound by an atom and is free to move.
AKA a delocalised electron
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Electrolytes
A liquid containing ions that are free to move and so conduct electricity
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Ionic Solutions
An ionic compound dissolved in a liquid
This forms an electrolyte
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Cations
A positively charged ion attracted to a cathode. (Which are negatively charged)
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Anion
A negatively charged ion attracted to an anode.
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Cathode and Anode
Cathode - a negatively charged electrode
Anode - a positively charged electrode
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Ammeter
A device used to measure electric current
Placed in series in a circuit and ideally has zero resistance
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Resistance
Property of a component calculated by divided the potential difference across it by the current in it.
Symbol R, unit ohm
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Potential Difference
Defined as the energy transferred from electrical to other forms per unit charge
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Conservation of charge
States electric charge cannot be created or destroyed
Total charge in any interaction is the same before and after said interaction
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Kirchhoff's First Law
At any point at a circuit the current entering is the same as the current leaving
Electrical charge is conserved
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Number Density
The number of free electrons per cubic metre of material.
Symbol n, unit 1/m-3
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Semi-conductors
A material with a lower number density than a typical conductor.
Number density typically of order 10 to the 17 1/m3
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Mean Drift Velocity
The average velocity of electrons as they move through a wire
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