Mains electricity part 1

Where is the elelctricity used to turn on home appliances like lamps or TVs coming from?

From the mains supply
The electricity enters our home through an underground cable
The cable is then connected to an electricity meter
From there the cable is connected to a consumer unit or fuse box

What is an electricity meter

a device that accurately records the transfer of energy from the national grid to the house.
Textbook: a device which measures the amount of electrical energy used

What is a consumer unit/fuse box?

a device which contains fuses or circuit breakers fo the various cicuits in your home

Most of the wires that leave the fuse box are connected to ___
How are individual pieces of electrical equipment (e.g TVs) connected to these circuits?

Ring main circuits (a ring circuit is an electrical wiring technique in which sockets and the distribution point are connected in a ring) that are hidden in the walls or floors around each room.
Using plugs

Ring main circuits consist of three wires. Which three?

• Basically in the sockets we can find these wires as the sockets are connected to the ring main circuit of our homes

The live wire, the neutral wire and the earth wire

Plugs and sockets in different countries look different but the principles of electrical wiring are similar

What is the voltage (mains electricity) supplied to homes?

230V. It ranges between 220V and 240V

Mains electricity has a _ voltage than cells and batteries used in mobile electrical appliances.
What would happen if you came into direct contact with mains electricity?

higher
You would receive an electric shock that might be fatal

What is used to avoid coming into direct contact with the mains electricity?

To prevent this the outer part of a plug, called the casing, is made from plastic, which is an insulator

What is the job of the live wire?

It provides a path along which the electrical energy (current) from the power station travels

What is the job of the neutral wire?

It completes the circuit

How is the earth wire different from the neutral and the live wire?

The earth wire usually has no current in it

What is the job of an earth wire? How does it work?

It is there to avoid people from receiving an electric shock (texbook: protects the user) if an appliance develops a fault by providing a path for current escape without passing through the user

How many brass pins are inside a socket? What is its job?

3
It provides an electrical connection (for the sockets) to the circuits

What are brass pins made of and why is it made from that?
What makes this material good to put on sockets?

Made from the metal brass (not in tbook: it is a copper and zinc alloy). Metal brass is a good conductor of electricity
Not in tbook pero me pareció adecuado: this material is good because it is low cost, has good electrical resistivity and good wear resistance

What is an alternating current or direct voltage?

A current that is constantly changing direction and magnitude/value

How would a graph showing an alternate current look like?

It would look like a wave

Why does the direction and magnitude of the voltage/current in AC change?

Because of the way the electricity is generated at the power station.

Where is AC used?

In mains electricity (your home)

What is a direct current or direct voltage?

A current that is always in the same direction and have the same value

What would a direct current look like on a graph?

A straight horizontal line

Where is direct current used?

Cells and batteries

What is a difference in the wires of a kettle and the big majority of the wires used around the house? Why?

Kettle wires are designed to have high resistances so that as the current passes through them, more energy is transferred and the elements heats up
Other wires in the house let current pass through it easily, they have low resistance, so that wires do not become warm when the appliances are being used

What are the wires in kettles and toasters commonly called?

Heating element

What are examples of other common appliances that make use of the heating effect of electricity?

Kettles, toaters, dishwashers, electric cookers, washing machines, electric fires and hairdryers

How does a traditional light bulb work?

When current passes through the thin wire, filament, of a traditional light bulb, it becomes very hot and glows white. The bulb is transferring electrical energy to heat and light energy

State two differences between the movement of charge in a device connected to domestic mains supply and a device connected to a battery

• Batteries use direct current while the domestic mains supply uses alternating current
• Mains has a bigger current because it has a higher voltage

Formula linking power voltage and current

Power (watts) = current (amps) x voltage (volts)
P = I x V