P2/Electricity Flashcards
describe resistance in a thermistor?
as temperature increases resistance decreases
where might a thermistor be used?
central heating system
oven
describe resistance in an LDR?
as light intensity increases resistance decreases
where might an LDR be used?
security lighting
describe current in a series circuit
it is the same current all the way round
describe potential difference in a series circuit
the total potential difference of the power supply is shared between the components
describe total resistance in a series circuit
the total resistance of the two components is the sum of the resistance of each component
what is the unit for resistance?
Ohm
what is the unit for potential difference?
volts
what is the unit for current?
amps
describe current in a parallel circuit
the total current through the whole circuit is the sum of the currents through the separate components
describe potential difference in a parallel circuit
it is the same across each component
describe total resistance in a parallel circuit
the total resistance of two resistors is less than the resistance of the separate components
what is the frequency of the UK mains supply?
50 Hertz
what is the potential difference of the UK mains supply?
230 volts
mains electricity is an a.c supply.
what does this mean?
current constant;y changes direction
what does d.c mean?
current flows in only one direction
what is needed for electrical charge to flow?
a potential difference
what is electric current?
a flow of charge
what determines the size of an electrical current?
the rate of flow of electrical charge
describe the current in a series circuit
it is the same all the way around