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PHYSICS UNIT 7 - ELECTRICITY (Series Circuits series2 sries3 (Cell…
PHYSICS UNIT 7 - ELECTRICITY 
Circuit symbols (see sheet)
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Parallel Circuits
Voltage
(potential difference) is same across all components V1 = V2 = V3 so identical bulbs in parallel will be same brightness
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Adding a resistor in parallel circuit reduces total resistance as current has more than one direction to go in
Series Circuits
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UK Domestic Electricity
Home
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National Grid
High potential difference & low current to transmit huge amount of power needed - so wires don't heat up & lose energy through thermal energy with high current
Transformers step up potential difference to 400 000V at one end & bring back down to safe, usable levels at other
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Parts of a Plug
Neutral wire - blue - completes the circuit & carries away current - electricity flows in through live wire & out through neutral wire (0V)
Earth wire - green & yellow - protects wiring & stops appliance casing from becoming live, only carries current when there's a fault (0V)
Live wire - brown - provides alternating potential difference (230V) from mains supply - gives electric shock as body 0V and large potential difference
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Formulae
OHM'S LAW
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Fuses
Typical sizes - 1A, 2A, 3A, 5A, 7A, 10A, 13A
A 5A fuse will melt if 5A passes through it & cut off electricity to the appliance - we usually choose a fuse just above current of the appliance
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To calculate fuse need for appliances use
eg. Fuse needed for 1.15KW electric fire at potential difference (voltage) of 230V = 1150 ÷ 230 = 5A so use 6A fuse