Electricity In The Home Flashcards
What does d.c. stand for?
Direct current.
What does a.c. stand for?
Alternating current. This means the current repeatedly reverses direction.
Where is a.c. current used?
It is found in the mains supply of electricity.
There is 50 cycles per second.
What is the first stage of The National Grid?
A power station which produces 25 000V of alternating potential difference.
What is the second step of The National Grid?
Step-up Transformers. They make the potential difference much bigger. They step it up to 132 000 volts. This also steps down the current. A lower current means that less energy is lost as heat in the cables.
What do the step down transformers do?
They supply the electricity from The National Grid to the consumers. Homes and offices get 230V whereas factories get 100kV.
What happens by making The National Grid large?
Less current is needed to transfer the same amount of power. Therefore, the power loss due to the resistance heating in the cable is much reduced.
Therefore, The National Grid is very efficient.
What does the earth wire do?
It stops the metal case becoming live if the wire breaks and touches the case.
Why are pugs coated in hard wearing electrical insulators (plastic)?
They contain live wires.
What is the earth wire?
It connects to the ground at your home. It has 0 volts and only carries a current only if there is a fault. It is the longest pin of a three pin plug. It is designed to contact the earth wire of a wall socket circuit. So, when you plug in an appliance with a metal case into a wall socket it is automatically earthed.
Why are the pins made of brass?
They are good conductors.
They don’t rust or oxide.
What is the brown wire connected to?
The live pin.
What is the blue wire connected to?
The neural pin.
What is the green and yellow stripe wire connected to?
The earth pin.
Why is copper used for the wires?
It is a good electrical conductor and it bends easily.
Why is plastic used to coat the wires?
It is a good electrical insulator, so if anyone touches the cable, it stops them from getting an electric shock.
What types of cables are used for appliances with plastic cases?
Two-core.
When are thicker wires used?
When more current passes brought them. This limits the resistance and stops the heating effect of the current making he wires too hot.
What is a short current?
Of a live wire touches a neutral wire, a very big current passes between the two wires at the point of contact. Provided he diss blows, it cuts the current off.
What does the current do?
When you use an electrical appliance, the current through it transfers energy to it from the power source it is connected to.
What is the power of an appliance, in watts?
Is the energy it transfers in joules per second.
What happens when an electric current passes through a resistor?
The power supplied to the resistor heats it. The resistor heats the surroundings, so the energy supplied is dissipated to the surroundings.
What is the current?
The charge that flows through it per second.
What is the potential difference?
The beefy transferred to the appliance by each coulomb of charge that passes through it.
