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20 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What current does a cell or battery provide and what does it mean How is it produced |
Dc - current only flows one way Produced by direct potential difference |
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What kind of electricity does the mains provide and what does it mean How is it produced What happens to the negative and positive terminals of ac power supply |
Ac - repeatedly reversed and produced by alternating potential difference Swap over with regular frequency |
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What is the frequency and voltage of the uks mains electricity supply |
50Hz 230V |
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List the components in a plug (4) What is the wire coatings, plug case, and wires made from and why |
Earth wire Neutral wire Fuse Live wire Plastic for wire coatings and plug case - good electrical insulator Copper for wires - good electrical conductors and bend easily |
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What does the earth wire do (3) |
For safety to stop appliance becoming live Voltage is 0V Only carries current if there’s a fault |
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What does the neutral wire do (2) |
Completes the circuit Potential difference is 0 |
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What does the fuse do (3) |
Connected to live wire If live wire touched neutral wire there’s a large current - short circuit Melts fuse and disconnects live wire from mains - keeps appliance safe |
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What is the national grid |
Nationwide network of cables and transformers that link power stations to consumers of mains electricity |
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What are transformers |
Devices change potential difference of alternating current |
Devices change potential difference of alternating current
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What type of potential difference do power stations produce and and at what voltage What is used to transfer it to transmission cables and what do they do Cables carry how much p.d. What is needed before electrical power reaches houses and what do we use |
Alternating p.d. at 25,000V Step up transformers increase voltage to 400,000V for cables to carry Step down transformers needed to turn voltage into 230V so its safe for homes and offices |
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Why do transformers improve efficiency What equation makes this true What does a lower current in cables mean and why |
High p.d. means lower current needed to transfer same amount of power Power = current x potential difference Lower current means less power wasted due to cables heating because: Power = current^2 x resistance |
Power x2 |
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What is power and resistance measured in |
Watts Ohms |
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List the components in a plug (4) What is the wire coatings, plug case, and wires made from and why |
Earth wire Neutral wire Fuse Live wire Plastic for wire coatings and plug case - good electrical insulator Copper for wires - good electrical conductors and bend easily |
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What does the earth wire do (3) |
For safety to stop appliance becoming live Voltage is 0V Only carries current if there’s a fault |
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What does the fuse do (3) |
Connected to live wire If live wire touched neutral wire there’s a large current - short circuit Melts fuse and disconnects live wire from mains - keeps appliance safe |
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What is the national grid |
Nationwide network of cables and transformers that link power stations to consumers of mains electricity |
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What type of potential difference do power stations produce and and at what voltage What is used to transfer it to transmission cables and what do they do Cables carry how much p.d. What is needed before electrical power reaches houses and what do we use |
Alternating p.d. at 25,000V Step up transformers increase voltage to 400,000V for cables to carry Step down transformers needed to turn voltage into 230V so its safe for homes and offices |
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Why do transformers improve efficiency What equation makes this true What does a lower current in cables mean and why |
High p.d. means lower current needed to transfer same amount of power Power = current x potential difference Lower current means less power wasted due to cables heating because: Power = current^2 x resistance |
Power x2 |
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What is power and resistance measured in |
Watts Ohms |
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If 100% efficiency assumed what’s the equation |
Primary p.d. x primary current = secondary p.d. x secondary current |
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