Physics Unit 2.4 Using mains electricity safely and the power of electrical appliances

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What is the power of an electrical appliance?
The rate at which it transforms energy.
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What is a circuit breaker? (part.1)
A circuit breaker is an electromagnetic device that breaks a circuit when the current goes above a certain value. When the current in a circuit increases, the strength of the electromagnet will also increase. This will pull the electromagnet.
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What is a circuit breaker? (part.2)
This will pull the electromagnet. As a result, spring 1 pulls apart the contact and disconnecting the circuit immediately, stopping current flow. The reset button can be pushed to bring the contact back to it's original position to reconnect circuit.
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What are the advantages & disadvantages of fuses?
Advantages: Simple, and cheap to replace. Disadvantages: Need replacement after each use. Slower to react.
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What are the advantages & disadvantages of circuit breakers?
Advantages: More reliable than fuses. Do not to be constantly replaced. Disadvantages: More expensive. More complicated than fuses.
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What is the voltage of the mains?
230V.
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What is the frequency of the mains, and what does this show?
50Hz, this shows that it goes backwards/ forwards 50 times a second.
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What is a direct current?
Supply is steady. Always same direction.
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Describe what happens during an alternating current.
Magnets spins, moves electrons, and spins copper.
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Describe the EARTH wire (green/yellow).
For safety purposes. Connected directly to earth. If there is a fault, it causes the current to go the earth wire, and away from the person.
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Describe the neutral wire (blue).
Almost 0V. This wire completes the main circuit (loop).
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Describe the live wire (brown).
This carries the voltage (230V (VERY dangerous)).
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Describe the fuse.
If there is a large current, this melts the fuse. Breaking the circuit, making the appliance safe. The earth wire and fuse together protect the wiring of the circuit.
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What is power?
How much energy is transferred to each section.
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Describe residual current circuit breakers.
They detect a difference in the current between the live and neutral wires. RCCBs work much faster than fuses do.
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Some appliances are double insulated, and therefore have no earth wire connection.
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The thicker the wire in the fuse, the higher the fuse's rating. This is because a thinner wire cannot take such a big load as a thicker one can; the thinner one will just melt at the same voltage.
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What happens when an electrical charge flows through a resistor?
The resistor gets hot.
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Why are compact fluorescent lamps more efficient than filament lamps?
Less energy is wasted on heating.
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Other cards in this set

Card 2

Front

What is a circuit breaker? (part.1)

Back

A circuit breaker is an electromagnetic device that breaks a circuit when the current goes above a certain value. When the current in a circuit increases, the strength of the electromagnet will also increase. This will pull the electromagnet.

Card 3

Front

What is a circuit breaker? (part.2)

Back

Preview of the front of card 3

Card 4

Front

What are the advantages & disadvantages of fuses?

Back

Preview of the front of card 4

Card 5

Front

What are the advantages & disadvantages of circuit breakers?

Back

Preview of the front of card 5
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