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

HideShow resource information
What is the power of an electrical appliance?
The rate at which it transforms energy.
1 of 19
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.
2 of 19
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.
3 of 19
Advantages: Simple, and cheap to replace. Disadvantages: Need replacement after each use. Slower to react.
4 of 19
Advantages: More reliable than fuses. Do not to be constantly replaced. Disadvantages: More expensive. More complicated than fuses.
5 of 19
What is the voltage of the mains?
230V.
6 of 19
What is the frequency of the mains, and what does this show?
50Hz, this shows that it goes backwards/ forwards 50 times a second.
7 of 19
What is a direct current?
Supply is steady. Always same direction.
8 of 19
Describe what happens during an alternating current.
Magnets spins, moves electrons, and spins copper.
9 of 19
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.
10 of 19
Describe the neutral wire (blue).
Almost 0V. This wire completes the main circuit (loop).
11 of 19
Describe the live wire (brown).
This carries the voltage (230V (VERY dangerous)).
12 of 19
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.
13 of 19
What is power?
How much energy is transferred to each section.
14 of 19
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.
15 of 19
Some appliances are double insulated, and therefore have no earth wire connection.
***
16 of 19
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.
***
17 of 19
What happens when an electrical charge flows through a resistor?
The resistor gets hot.
18 of 19
Why are compact fluorescent lamps more efficient than filament lamps?
Less energy is wasted on heating.
19 of 19

## 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)