Current electricity

Parallel circuits

each component is separatly connected to the positive and negative of the supply
if you disconnect one of the components it will hardly affect the others
all the components get a full source of voltage so the voltage is the same all the way across (V1 = V2 = V3)
the total current is equal to the total of all the currents though the separate components (A = A1 + A2 + A3)
there are junctions where the current splits and rejoins
the total current going into a junction has to equal the total current leaving
ammeters are always connected in series even in a parallel circuit
voltmeters are always connected in parallel even in series

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connect in a line between the negative and positive of the power supply
if you remove or disconnect one component the circuit is broken
the total P.d of the supply is shared between the various components
the voltage around a series circuit always adds up to equal the sources voltage (V = V1 + V2 + V3)
the same current flows through all parts of the circuit (A1 = A2)
the total resistance is the sum of all resistances (R = R1 + R2)
the bigger the resistance of a component then there is a bigger share of the total P.d

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voltage and current graphs show how the current varies as you change the potential difference
filament lamp graph shows as the temperature increases the resistance increases
a diode only lets the current flow in one direction
resistance increases with temperature
P.d = current X resistance (V = I x R)

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the ammeter measures the current flowing though the component and must be placed in series
the voltmeter measures the potential difference and must be placed in parallel

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current is the flow of electrical charge
it will only flow if there is a potential difference across it
potential difference is the force that pushes the current around
resistance is anything in the circuit which slows the flow down
the greater the resistance, the smaller the current flows
current = charge (divided by) time (Q = I x T)
potential difference across an electrical component is the energy that is transferred by the electrical component per unit of charge
P.d = work done (divided by) charge
W = V x Q

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caused by friction
when insulating materials are rubbed together, negatively charged electrons will be scraped off one and dumped on the other
this leaves a positive static charge on one and a negative charge on the other
electricity charged objects attract small objects placed near them
both negative and positive electrostatic charges are only ever produced by the movement of electrons
positive charges are caused by electrons moving away
two things with opposite electrical charges are attracted to each other
electrical charges can move easily though some metals known as conductors

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