Mains Electricity

Question 1

What is the frequency mains electricity is generated at and voltage it’s delivered to houses in

Answer 1

50Hz
230V

Question 2

How does a direct current look in a voltage time graphs

Answer 2

As a straight line

Question 3

How does an alternating current look on a voltage time graph

Answer 3

As a wavey line
Alternating.between postitive and negative values

Question 4

Why are the wires made out of copper?

Answer 4

Because they are good conductors

Question 5

Why are the wires coated with plastic

Answer 5

Because it’s a good insulator

Question 6

What is the outer insulation of a cable for?

Answer 6

Wraps the three wires in the cable with extra insulation for safety

Question 7

What is the cable grip of a plug for?

Answer 7

Holds the cable tightly so the wires don’t become loose

Question 8

What is the live wire?

Answer 8

The brown plastic that coats a copper wire along which current enters the device

Question 9

What is a fuse?

Answer 9

Glass or ceramic canister that has a thin wire that melts inside if current gets too high

Question 10

What is a neutral wire?

Answer 10

Blue plastic plastic that coats a copper wire that connects to the cable in the wall and completes the circuit

Question 11

What is the Earth wire?

Answer 11

Striped plastic coated copper wire that provides a path for current to flow from the case of device to ground if there is a fault

Question 12

How does the Earth wire prevent the user from getting electrocuted?

Answer 12

The Earth wire is connected to the case and is attached to a water pipe underground
Because the wire is made of copper the Earth wire provides a low reisistnce path to the ground
So if anything goes wrong the live wire current passing through the case will pass through the ground instead of the person

Question 13

How does a fuse work when a fault happens?

Answer 13

If there is a fault a large currrent will flow through the low resistance Earth wire
This causes the fuse to melt
Since the fuse is melted the circuit is broken and no more current flows through the device

Question 14

What does the national grid do?

Answer 14

Distribute electricity across the county

Question 15

How is electricity in national power grid produced?

Answer 15

With a generator or another method

Question 16

What are transformers used for?

Answer 16

Used to change voltages and currents in transmission lines

Question 17

How are transformers made?

Answer 17

Two coils of wire around a magnetic core

Question 18

What does the number of coils on a transformer determine?

Answer 18

If it’s a step up or step down transformer of voltage

Question 19

What happens to current as voltage increases?

Answer 19

Is decreases current

Question 20

What happens to voltage as current increases?

Answer 20

It decreases voltage

Question 21

What does a step up transformer do?

Answer 21

Increases voltage and reduce current

Question 22

How much does a step up transformer increase voltage and what does this do?

Answer 22

25000V-400000V causing current to decrease
Meaning less energy is lost through heating the wire

Question 23

What is used to keep high voltage wires safe from people?

Answer 23

Pylons to keep transmission lines above the ground

Question 24

How much does a step down transformer reduce voltage by?

Answer 24

230V

Question 25

What happens to transmission lines as electric current flows through it?

Answer 25

Electrons flow through the cable and they get hot and dissipate energy to the surroundings

Question 26

How do you ensure minimal power is lost from the cables?

Answer 26

Make cables are thick so resistance is low
High voltages are used to reduce the current through the transmission lines

Question 27

How does having a low resistance and low current affect power delivered to consumer?

Answer 27

The wires won’t heat up as much so most of the power is delivered to the customer