P5 - Electricity In The Home

Question 1

What are the two types of electricity supply?

Answer 1

Alternating current (ac) and Direct current (dc)

Question 2

What is alternating current?

Answer 2

Current that is constantly changing direction

Question 3

What produces alternating currents?

Answer 3

Alternating voltages

Question 4

Is the electricity in our home ac or dc supply?

Answer 4

AC

Question 5

What voltage is the AC supply in our homes?

Answer 5

230V

Question 6

What frequency of the AC supply in our homes?

Answer 6

50Hz

Question 7

Where can dc supply be found?

Answer 7

Cells and batteries

Question 8

What is direct current?

Answer 8

Current that is always flowing in one direction

Question 9

What is direct current created by?

Answer 9

Direct voltage

Question 10

What colour is the live wire?

Answer 10

Brown

Question 11

What colour is the neutral wire?

Answer 11

Blue

Question 12

What colour is the earth wire?

Answer 12

Green and yellow

Question 13

What does the live wire do?

Answer 13

Provides the alternating potential difference at 230V from the mains supply

Question 14

What does the neutral wire do?

Answer 14

It just completes the circuit and is at 0V

Question 15

What does the earth wire do?

Answer 15

For protecting the wiring and for safety. Its at 0V

Question 16

What is the voltage or a normal human being?

Answer 16

0V

Question 17

What is the equation that links energy transferred, charge flow and potential difference?

Answer 17

E = QV

Question 18

What is the equation linking power, potential difference and current?

Answer 18

P = VI

Question 19

What is the equation to find out power without knowing the potential difference?

Answer 19

P = I*2 x R

Question 20

What does the national grid do?

Answer 20

Transfers electrical power from power stations anywhere on the grid anywhere else that needs it

Question 21

What do you need in a circuit to transmit huge amount of power?

Answer 21

A high potential difference or a high current

Question 22

What is the problem of a high current?

Answer 22

Energy will be lost as it is transferred to thermal energy to the surroundings

Question 23

What is the national grid exactly?

Answer 23

Giant system of wires that covers Britain.
It generates electricity from power stations to homes everywhere

Question 24

.

Question 25

When would a demand for electricity increase?

Answer 25

When its dark or cold outside When people come home from work or school A popular event is on TV

Question 26

What is the structure any transformer?

Answer 26

A primary coil and a secondary coil joined together with an iron ore

Question 27

What is an equation to express the power of a primary coil in a transformer?

Answer 27

Power = potential difference x current

Question 28

How efficient are transformers?

Answer 28

Nearly 100% efficient

Question 29

Because transformers are nearly 100% efficient, whats the relation between the primary and secondary coil?

Answer 29

Power in primary = power in secondary

Question 30

What is static electricity?

Answer 30

The build up of charge on an objects surface

Question 31

If two normal objects, like a bag and a hat, are rubbed together, what happens to the electrons?

Answer 31

The friction between them causes electrons to be rubbed off one of them (like the hat) and on to the other one (like the bag)

Question 32

If two conducting materials, like metals , are rubbed together, what happens to the electrons?

Answer 32

The electrons just flow back and forth This means no charge ever builds up

Question 33

If two insulating materials, like a cloth and a polystyrene rod , are rubbed together, what happens to the electrons?

Answer 33

The electrons cant flow back so the transfer caused by the friction gives a POSITIVE static charge on the material that lost the electrons and a NEGATIVE static charge on the material that gained the electrons

Question 34

In static electricity which electrons are being transferred?

Answer 34

Only the negative electrons are being transferred

Question 35

What happens when an object keeps on gaining negative electrons?

Answer 35

More electrons transferred and the size of the charge increases leads to potential difference between the charged material and the earh

Question 36

What happens when the potential difference between the charged object and earth object is large enough?

Answer 36

Electrons can jump across the gap We see this as a spark

Question 37

What are the three 'fields'?

Answer 37

Electric fields Gravitational fields Magnetic fields

Question 38

How can you draw the electrical field around an object?

Answer 38

Draw electric field lines

Question 39

How do electrical field lines show the electric field?

Answer 39

Arrows facing out are positive Arrows facing in are negative The close the arrows are, the stronger the field

Question 40

What happens in the interaction between electric fields and air

Answer 40

A strong electric field can cause surrounding air particles to lose electrons and become positively charged