P5 Electricity in the home

Question 1

What is direct current?

Answer 1

Current which flows in one direction

Question 2

What is alternating current?

Answer 2

Current which can repeatedly reverse its direction of flow

Question 3

What are the two types of wire in a live circuit?

Answer 3

• Live wire (alternatively positive and negative every cycle)
• Neutral wire (wire at zero volts)

Question 4

What is the peak potential difference of an alternating current supply?

Answer 4

The maxium voltage measured from zero vaults

Question 5

How do you measure the frequency of an alternating current supply?

Answer 5

Frequency = 1 / time taken for one cycle

Question 6

What are socket and plug cases made of?

Answer 6

Stiff plastics that enclose electrical connections as plastic is a good electrical insulator

Question 7

What is a mains-cable made of?

Answer 7

Two or three insulated copper wires surrounded by an outer layer of flexible plastic material

Question 8

What is the power supplied to a device?

Answer 8

The energy transferred to it each second

Question 9

How do you find electrical power supplied to an appliance?

Answer 9

Power = Amps x Voltage

Question 10

How do you calculate charge flow?

Answer 10

Charge flow = current x time

Question 11

When charge flows through a resistor…..

Answer 11

energy transferred to the resistor makes it hot

Question 12

How do you calculate energy transferred to a component?

Answer 12

Energy = potential difference x charge flow

Question 13

What does a domestic electricity meter measure?

Answer 13

Energy supplied

Question 14

How do you calculate useful energy used?

Answer 14

Useful energy used = efficiency x energy supplied

Question 15

Why are pylon cables made of aluminium?

Answer 15

• They are light and highly condusive
• They are less resistant

Question 16

What are the advantages of overheard cable?

Answer 16

• Relatively cheap to link between tall towers
• Easy access to maintain cables
• Open to air cooling of cables

Question 17

What are the disadvantages of overheard cable?

Answer 17

• Visually unappealing, (ruin landscapes)
• Vulnerable to the weather
• Must cut across large amount of land

Question 18

What are disadvantgaes of Underground Power Cables?

Answer 18

• Very expensive to put miles and miles of cable underground
• Maintenance would be harder as you would have to dig them up
• The cables can get hot, hard to cool underground therefore must be thicker
• Would need to clearly mark everywhere they are to reduce the risk of accidentally digging it out

Question 19

Batteries use…

Answer 19

DC currents (Direct Current)

Question 20

Plugs use…

Answer 20

AC current (Alternating Current)

Question 21

What is Direct Current (DC)?

Answer 21

The current flows in one direction only.

• E.g. cells & batteries

Question 22

What is Alternating Current (AC)?

Answer 22

When the current constantly changes direction

E.g. mains supply, the power socket