Chapter 5 Electricity In Homes

Question 1

5.1 Direct current definition

Answer 1

The current goes in 1 direction

Question 2

5.1 Alternating current definition

Answer 2

The current repeatedly reverses its direction of flow.

Question 3

5.1 What is a step up transformer?

Answer 3

They use power stations to transfer electricity to the National Grid. It increases the potential difference.

Question 4

5.1 Step-down transformer

Answer 4

They supply electricity to National Grid consumers and decrease the potential difference.

Question 5

5.1 What is the peak potential difference of an A.C supply?

Answer 5

The maximum voltage measured from 0 volts.

Question 6

5.1 How to measure the frequency of AC current

Answer 6

1/time taken for 1 cycle

Question 7

5.2 What is the Live wire

Answer 7

It is a brown colour which carries the potential difference and it repeatedly changes from + to -

Question 8

5.2 Neutral wire

Answer 8

It is a blue colour and is earthed at the local electricity substation. It does not carry any voltage

Question 9

5.2 Why is plastic used in plug casesand enclose electrical connections.

Answer 9

It is a good electrical insulators.

Question 10

5.2 What is an Earth Wire

Answer 10

It is a green and yellow colour that stops the metal case becoming live if the live wire breaks.

Question 11

5.2 What is a short circuit?

Answer 11

If a live wire and a neutral wire touch in an appliance. The fuse blows which cuts the current off.

Question 12

5.2 What is an electric shock?

Answer 12

When someone touches a live wire, a big potential difference will act across their body, causing a current to flow through them.

Question 13

5.3 Power equation

Answer 13

Energy transfer/time

Question 14

5.3 Power supplied equation

Answer 14

Current x potential difference

Question 15

5.3 Power equation with a resistor

Answer 15

Current^2 x resistance

Question 16

5.1 Mains circuit

Answer 16

It has a live wire and a neutral wire when a current goes through a mains appliance alternates.

Question 17

5.4 How to calculate charge flow

Answer 17

Current x time

Question 18

5.4 What happens when current goes through a resistor? Talk about energy

Answer 18

Energy is transfered to the resistor so the resistor becomes hotter

Question 19

5.4 When charge flows around a circuit, what happens to the energy supplied by the battery

Answer 19

It is equal to the energy transfered to all components of the circuit.

Question 20

5.5 Energy transfered from the mains equation

Answer 20

Power x time

Question 21

5.5 Power equation

Answer 21

Current x potential difference

Question 22

5.5 Energy efficiency equation

Answer 22

Output energy/input energy x 100

Question 23

5.5 Output power equation

Answer 23

Efficiency x its input power

Question 24

5.5 What is a domestic electricity meter used for

Answer 24

Measure how much energy is supplied.

Question 25

How do electrical appliances waste energy?

Answer 25

• The wires and the components has a heating effect due to resistance of the wires and the components.
• This transfers heat energy to the surroundings.
• Also, electrical devices with moving parts such as electric motors also waste energy due to friction in moving parts.
• Friction between the moving parts heats them, so they transfer energy by heating the surroundings.