Electric current - the rate of flow of electric charge
What is current measured in
Amps
What is charge measured in
Coulombs
What is potential difference measured in
Volts
what is resistance measured in
Ohms
Resistor
greater the potential difference the greater the current
resistance is constant
Lamp
As it gets hotter it gives out more light
So there is more resistance
Diode
only let’s current flow in one direction
high potential difference means lots of current can flow through
Light dependant resistor
as we increase light intensity
resistance decreases
Thermistor
as we heat it up
light intensity decreases
Series circuit
same amount of current around whole circuit
Potential difference will equal what it was at the start
Total resistance is all resistance flowing through
Parallel
current splits at junction
different amount of current around whole circuit
The potential difference is the same through whole circuit
What’s the voltage in the uk mains
230
How many Hz in the uk mains
50
Brown wire
Live wire
Blue wire
Neutral wire
Green and yellow wire
Earth wire
National grid - system of cables and transformers linking power station to consumers
Step up transformers - Increase voltage
Step down transformers - reduce voltage
Each wire in the plug is made out of copper and is covered in insulatingplastic for safety
Whats does the live wire do
provides alternating potential difference and has 230v
What does the neutral wire do
completes the circuit by carrying current away and has 0v
What does the earth wire do
stops appliance casing from becoming live by providing an alternative pathway for current to flow away
Earth wire doesn’t normally have a current
Earth wire has a potential difference of 0v
How does casing from a wire become live
If live wire came loose and touched the casing
Which wire supplies the current to the appliance
Livewire
Which wire completes the circuit allowing current to flow
Neutral wire
Fossil fuel and nuclear power stations work by generating thermal energy. Water is turned into steam which can rise and spin turbines. Kinetic energy can be converted to electrical energy
high current causes wire to heat up meaning that energy is lost as heat to surroundings
Step up transformers
increase voltage
decrease current
High voltage
is dangerous
blows household appliances
Step up transformers increase voltage to 400000v
Step down transformers reduce voltage to 230v
We use low current and high voltage to reduce energy loss
voltmeter always connected in parrel to components
ammeter always connected in series with components