Electricity

Question 1

What is direct current (d.c)?

Answer 1

The current only flows in one direction and is produced by a direct potential difference.

Question 2

What provides direct current?

Answer 2

A cell or battery.

Question 3

What provides an alternating current?

Answer 3

Mains electricity.

Question 4

What is alternating current (a.c)?

Answer 4

The current repeatedly reverses direction and is produced by an alternating potential difference.

Question 5

What is the frequency of the mains electricity supply in the UK?

Answer 5

50Hz.

Question 6

What is the voltage of the mains electricity supply in the UK?

Answer 6

230V.

Question 7

What is the colour of the live wire in a plug?

Answer 7

Brown.

Question 8

What is the colour of the neutral wire in a plug?

Answer 8

Blue.

Question 9

What is the colour of the earth wire in a plug?

Answer 9

Green/yellow.

Question 10

What does the fuse in a plug do?

Answer 10

It melts and blows if too much current flows after the live wire touches the neutral wire.

Question 11

What is the role of the neutral wire?

Answer 11

Provides a return path for the current to the

substation.

Question 12

What is the role of the earth wire?

Answer 12

A safety wire to prevent the appliance from becoming live and provides a low resistance path to the ground.

Question 13

What is the potential difference of the live wire?

Answer 13

230v

Question 14

What is the potential difference of the neutral wire?

Answer 14

0v

Question 15

What is the potential difference of the earth wire?

Answer 15

0v and only carries current if there is a fault.

Question 16

What is used the wire coatings in a plug and why?

Answer 16

Plastic because its a good electrical insulator.

Question 17

What is used for the wires in a three-core cable and why?

Answer 17

Copper because its a good electrical insulator and bends easily.

Question 18

What is the National Grid?

Answer 18

A network of cables and transformers that carries the electricity generated by power stations and renewable energy generators to homes and other buildings.

Question 19

What are transformers?

Answer 19

Devices that can change the potential difference of an alternating current.

Question 20

How much do power stations produce electricity at an alternating potential difference of?

Answer 20

25,000v.

Question 21

How much electrical power do the cables in the National Grid transfer?

Answer 21

400,000v.

Question 22

What are step-up transformers used for?

Answer 22

Used to increase the potential difference from the power station to the transmission cables.

Question 23

What are step-down transformers used for?

Answer 23

Used to decrease the potential difference from the transmission cables to the mains supple in buildings so it is safe to use.

Question 24

What are the advantages of using overhead electrical cables?

Answer 24

• Cheaper to install.

- Easier to repair.

Question 25

What are the disadvantages of using overhead electrical cables?

Answer 25

- Damaged by wind. | - Visual pollution.

Question 26

What are the advantages of using underground electrical cables?

Answer 26

- No visual pollution. - Not damaged by wind. - No one gets electrocuted. - Cannot be pulled out by people.

Question 27

What are the disadvantages of using underground electrical cables?

Answer 27

- More expensive to install. | - Harder to repair.

Question 28

What charge does an atom have and why?

Answer 28

No charge because it has an equal numbers of positive protons and negative electrons.

Question 29

When can insulating materials become charged?

Answer 29

When they are rubbed with another insulating material because electrons are transferred from one material to another.

Question 30

What happens if a charged object is placed in the electric field of another object?

Answer 30

It experiences electrostatic force and the 2 charged objects exert a non-contact force on each other.

Question 31

What does a series circuit look like?

Answer 31

The components are connected one after the other in a single loop.

Question 32

In a series circuit what happens if one component stops working?

Answer 32

The whole circuit stops working.

Question 33

What does a parallel circuit look like?

Answer 33

Made up of 2 or more loops.

Question 34

What happens in a parallel circuit if one branch stops working?

Answer 34

The other branches will not be affected.

Question 35

What are the rules of a series circuit?

Answer 35

- Resistance is added together. - Current is the same everywhere. - Voltage is shared.

Question 36

What are the rules of a parallel circuit?

Answer 36

- The resistance gets lower the more resistors you add and is never higher than the lowest resistor value. - The current is shared. - The voltage is the same everywhere.

Question 37

What is Ohms law?

Answer 37

The current through a component depends on the resistance and the potential difference. The greater the resistance of the component, the smaller the current for a given potential difference.

Question 38

What is resistance?

Answer 38

A measure of how difficult it is for current to flow through a resistor.

Question 39

What happens to the current in an electrical circuit if the resistance is increased?

Answer 39

The current decreases.

Question 40

What happens to the current in an electrical circuit if the potential difference is increased?

Answer 40

The current will also increase.

Question 41

What is current?

Answer 41

The movement of electrons.

Question 42

What is an electrical insulator?

Answer 42

A material that doesn't allow the flow of electric charges/currents to pass through it.

Question 43

what is a conductor?

Answer 43

A material that allows electric currents to pass through it.

Question 44

what is potential difference?

Answer 44

A measure of how much energy is transferred between 2 points in a circuit.