Summary AQA GCSE Physics Combined Science - Electricity Notes

ELECTRICITY

CIRCUITS
 Current flows positive to negative
 SERIES CIRCUIT
o The current is the same everywhere
o Potential difference/voltage is shared
o Total resistance = all resistance added together
o Closed circuit
o 1 loop
 PARALLEL CIRCUIT
o The current is shared
o Potential difference/voltage is the same across each branch
o Branched circuit
o Total resistance is less than the branch with the smallest resistance
 Two resistors in parallel will have a smaller overall resistance than just one
 This is because the charge has more than one branch to take, so only some
charge will flow along each branch




RESISTANCE
 Ohm' s law: the current is directly proportional to the voltage and inversely proportional to
the resistance
 Resistance increases as current decreases
 Resistance decreases as temperature increases
 The greater the length of the wire, the more the resistance and the lower the current
 The greater the light intensity, the lower the resistance




DOMESTIC USES AND SAFETY
 MAINS
o Mains electricity is an AC supply
o In the UK the domestic electricity supply has a frequency of 50Hz and is about 230V
o AC = alternating current, the current continuously varies
o DC = direct current, the charge flows in one direction
 CABLING
o Live wire
 Brown
 230V
 Carries the alternating PD from the supply