P2.4

Question 1

What items use a direct current?

Answer 1

~ Phones
~ Laptops
~ Torches

Question 2

What are the two types of electric current?

Answer 2

~ Direct current (D.C.)

~ Alternating current (A.C.)

Question 3

What type of current is supplied by the mains?

Answer 3

Alternating current

Question 4

What does alternating current do?

Answer 4

~ Repeatedly reverses direction
~ So flows one way and then the opposite way in cycles
~ The number of cycles per second is called the frequency

Question 5

What is the frequency of alternating current in the U.K.?

Answer 5

50 Hz (50 cycles per second)

Question 6

What is the voltage of alternating current in the U.K.?

Answer 6

230 V

Question 7

What is an oscilloscope?

Answer 7

A machine that shows readings on potential difference and current

Question 8

What is a period in alternating current?

Answer 8

The time taken for 1 cycle (on a graph the line curving above and then below the line)

Question 9

What is a 3 core cable?

Answer 9

A cable with 3 copper wires (red, green + yellow stripes, blue)

Question 10

What is a 2 core cable?

Answer 10

A cable with 2 copper wires (blue and brown)

Question 11

How is a plug made safe?

Answer 11

~ Tough case + cable made of plastic (good insulator)
~ Cable/cord grip holds cable in place
~ Fuse which will melt if the current gets too high

Question 12

What colour is the live wire in a plug?

Answer 12

Brown

Question 13

What colour is the neutral wire in a plug?

Answer 13

Blue

Question 14

What colour is the earth wire in a plug?

Answer 14

Green + yellow stripes

Question 15

What appliances do 2 core cables connect to?

Answer 15

Double insulated appliances like hairdryers (those with a non-metal outer casing)

Question 16

What appliances do 3 core cables connect to?

Answer 16

Appliances with metal casing like kettles

Question 17

How are we protected from electric shocks from the live wire in a 2 cable

Answer 17

There are two cases of insulating plastic between the live wire and the outside of the appliance

Question 18

How can the earth wire prevent the metal casing of an appliance causing electric shocks by the live wire becoming loose and touching the metal case?

Answer 18

~ It is connected to the casing
~ The current would be directed through the earth wire, back to the plug and into the ground
~ The fuse will blow quickly

Question 19

What does a RCCB do?

Answer 19

They switch off the current in dangerous situations

Question 20

How do a RCCB work?

Answer 20

Detects a difference in current between the live wire and the neutral wire

Question 21

Why is using an RCCB better than a fuse?

Answer 21

~ Faster

~ Can be re-set

Question 22

What sort of appliances have no earth wire?

Answer 22

Double insulted ones

Question 23

When does a resistor get hot?

Answer 23

When an electrical charge flows through it

Question 24

What happens to a wire carrying a current?

Answer 24

It gets warmer

Question 25

Why do bigger appliances have thicker cables?

Answer 25

To reduce the heat produced through the wire

Question 26

What is the problem with filament lamps?

Answer 26

Gets very hot which makes it glow, but the heat energy is wasted

Question 27

What is good about Compact Fluorescent Lamps?

Answer 27

~ Produce less heat

~ So more efficient and less wasteful