2. Electricity (electricity in the home & static electricity)

Question 1

What does Alternating current do (AC)?

Answer 1

It repeatedly changes direction and voltage

Question 2

What is Direct current (DC)?

Answer 2

Current that is always flowing in the same direction. It’s created by a direct voltage

Question 3

What are the 3 wires in most cables?

Answer 3

• Earth wire
• Live wire
• Neutral wire

Question 4

What colour is the live wire?

Answer 4

Brown

Question 5

What colour is the neutral wire?

Answer 5

Blue

Question 6

What colour is the earth wire?

Answer 6

Green with yellow stripes

Question 7

What is the voltage of the earth wire?

Answer 7

0v

Question 8

What is the voltage of the neutral wire?

Answer 8

0v

Question 9

What does the neutral wire do?

Answer 9

It completes the circuit by carrying current away from the live wire

Question 10

What is the earth wire and what does it do?

Answer 10

A safety wire, it stops the appliance from becoming live

Question 11

What does the live wire do?

Answer 11

It provides the alternating potential difference at about 230V from the mains supply

Question 12

Why can a connection between live and earth wires be dangerous?

Answer 12

The connection creates a low resistance path allowing a lot of current to flow through, causing a spark

Question 13

What is the equation that links energy transferred, power and time?

Answer 13

E = PT
Energy transferred (J) = power (W) x time (s)

Question 14

What is a power rating?

Answer 14

The maximum safe amount of energy an appliance can operate at

Question 15

What is the equation linking energy transferred, charge and voltage?

Answer 15

E = QV
Energy (J) = charge (C) x voltage (V)

Question 16

What is the equation linking power, voltage and current?

Answer 16

P = VI
Power (W) = voltage (V) x current (A)

Question 17

What is the equation linking power, current and resistance?

Answer 17

P = I^2 x R
Power (W) = current squared (A) x resistance (ohms)

Question 18

What is the National grid?

Answer 18

The nationwide network of cables and transformers that connects power stations and consumers

Question 19

Why is the National grid an efficient way of transferring energy?

Answer 19

As they have a high p.d and decreased current, so less energy is lost through heating

Question 20

What do step-up transformers do?

Answer 20

Increase the p.d

Question 21

What do step-down transformers do?

Answer 21

Decrease the p.d

Question 22

What is static electricty?

Answer 22

• The build up of charge on an insulated object
• When two insulating objects are rubbed against one another, this causes electrons to transfer, from one object to another
• Resulting in a positively charged object and a negatively charged object, that are attracted to one another

Question 23

What charges are the polythene rod and duster?

Answer 23

• Polythene rod: negatively charged
• Duster: positively charged

Question 24

What charges are the acetate rod and the duster?

Answer 24

• Acetate rod: positively charged
• Duster: negatively charged

Question 25

What is an electric field?

Answer 25

A field created around any electrically charged object

Question 26

What happens when a charged object is brought in the electric field of another object?

Answer 26

A force is felt

Question 27

Why can static charge cause sparks?

Answer 27

The potential difference between the charged object of 0v can be large enough to create a spark. The potential difference causes a strong electric feild causing ionisation of the air, hence a current can flow through resulting in a spark

Question 28

What does the positive electric field look like?

Answer 28

Question 29

What does the negative electric field look like?

Answer 29