Electricity In The Home

Question 1

What does d.c. stand for?

Answer 1

Direct current.

Question 2

What does a.c. stand for?

Answer 2

Alternating current. This means the current repeatedly reverses direction.

Question 3

Where is a.c. current used?

Answer 3

It is found in the mains supply of electricity.

There is 50 cycles per second.

Question 4

What is the first stage of The National Grid?

Answer 4

A power station which produces 25 000V of alternating potential difference.

Question 5

What is the second step of The National Grid?

Answer 5

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.

Question 6

What do the step down transformers do?

Answer 6

They supply the electricity from The National Grid to the consumers. Homes and offices get 230V whereas factories get 100kV.

Question 7

What happens by making The National Grid large?

Answer 7

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.

Question 8

What does the earth wire do?

Answer 8

It stops the metal case becoming live if the wire breaks and touches the case.

Question 9

Why are pugs coated in hard wearing electrical insulators (plastic)?

Answer 9

They contain live wires.

Question 10

What is the earth wire?

Answer 10

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.

Question 11

Why are the pins made of brass?

Answer 11

They are good conductors.

They don’t rust or oxide.

Question 12

What is the brown wire connected to?

Answer 12

The live pin.

Question 13

What is the blue wire connected to?

Answer 13

The neural pin.

Question 14

What is the green and yellow stripe wire connected to?

Answer 14

The earth pin.

Question 15

Why is copper used for the wires?

Answer 15

It is a good electrical conductor and it bends easily.

Question 16

Why is plastic used to coat the wires?

Answer 16

It is a good electrical insulator, so if anyone touches the cable, it stops them from getting an electric shock.

Question 17

What types of cables are used for appliances with plastic cases?

Answer 17

Two-core.

Question 18

When are thicker wires used?

Answer 18

When more current passes brought them. This limits the resistance and stops the heating effect of the current making he wires too hot.

Question 19

What is a short current?

Answer 19

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.

Question 20

What does the current do?

Answer 20

When you use an electrical appliance, the current through it transfers energy to it from the power source it is connected to.

Question 21

What is the power of an appliance, in watts?

Answer 21

Is the energy it transfers in joules per second.

Question 22

What happens when an electric current passes through a resistor?

Answer 22

The power supplied to the resistor heats it. The resistor heats the surroundings, so the energy supplied is dissipated to the surroundings.

Question 23

What is the current?

Answer 23

The charge that flows through it per second.

Question 24

What is the potential difference?

Answer 24

The beefy transferred to the appliance by each coulomb of charge that passes through it.

Question 25

What is the power supplied?

Answer 25

The energy transferred to it each second. The energy transferred by an electric current per second.

Question 26

What happens when charge flows through a resistor?

Answer 26

Energy is transferred to the resistor, so the resistor becomes hotter.

Question 27

Why do electrical appliances waste energy?

Answer 27

The current in both of the wires and the components of the appliance has a heating effect due to the resistance of the wires and components. So they transfer energy to the surroundings.

Question 28

What is a fuse?

Answer 28

A deliberate weak link in the circuit. If a fault occurs and too much current flows to an appliance, the rise will melt. This breaks the circuit and stops the danger of fire or electric shock.

Question 29

What is a circuit breaker?

Answer 29

A safety device. If too much current flows trough a circuit it should cut off the current if the current is large, the iron bad is pulled to the electromagnet, therefore, breaking the circuit. It should only be out in the live wire. It will easily reset which means it is easier to use than a fuse.

The electromagnet attracts the iron, therefore breaking the circuit.

Question 30

What is a residual current circuit breaker?

Answer 30

It compares the current in and out of an appliance and breaks the circuit if they are different. They prevent electric shock more effectively because it acts much faster than a fuse.