Chapter 8 - Charge And Current Flashcards
Electric current
The rate of flow of charge, symbol I, measures in amperes A: a normal flow of electrons or flow of ions in electrolytes
Electric charge
A physical property, symbol q or Q, either positive or negative, measured in coulombs C or as a relative charge
Positive charge
A type of electric charge - positively charged objects attract negatively charged ones and repeal other positive charges
Negative charge
A type of electric charge, negatively charged objects attract positively charged ones and repel other negative ones
Coulombs
The derived SI unit of electrical charge, symbol C - 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere 1C=1A
Ions
An atom that has either lost or gained electrons and so has a net charge
Relative charge
A simplified measurement of the electric charge of a particle or object, measured as multiples of elementary charge
Elementary charge
The electric charge equivalent to the charge on a proton, 1.60x10^-19C symbol e
Quantisation
The availability of some quantities, such as energy or charge, only in certain discrete values
free electrons/delocalised electron
An electron in a metal that is not bound to an atom and is free to move
Conventional current
A model used to describe electric current in a circuit - conventional current travels from positive to negative - the direction in which positive charges would travel
Electrolytes
A liquid containing ions that are free to move and so to conduct electricity
Ionic solution
An ionic compound dissolved in a liquid to form an electrolyte
Cation
A positively charged ion, which is attracted to a cathode
Anion
A negatively charged ion, which is attracted to an anode
Anode
A positively charged electrode
Cathode
A negatively charged electrode
Ammeter
A device used to measure electric current-it must be placed in series and ideally have zero resistance
Resistance
A property of a component calculated by dividing the potential difference across it by the current in it, symbol R, unit ohm (horse shoe shape)
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
Kirchoff’s first law
At any point in an electrical circuit, the sum of the e.m.fs is equal to the sum of the p.d’s. Current in=current out EI in = EI out
Number density
The number of free electrons per cubic meter of material, symbol n, unit m^-3
Semiconductor
A material with a lower number density than a typical conductor, e.g. Silicon
Mean drift velocity
The average velocity of electrons as they move through a wire, symbol v unit ms^-1
