electricity in the home

Question 1

what is ac?

Answer 1

current that constantly changes direction alternating current because of alternating voltage

Question 2

what is dc?

Answer 2

current that constantly flows in the same direction direct current

Question 3

what is the voltage and hertz of UK mains power?

Answer 3

230V.
50hz.

Question 4

what is hertz hz

Answer 4

how many times ac switches direction every second.

Question 5

what is a 3 core cable?

Answer 5

a cable with 3 wires.

Question 6

what are the wire colours in a 3 core cable? (3)

Answer 6

brown. live
blue. neutral
green and yellow. earth

Question 7

what is the purpose of the live wire?

Answer 7

to supply an alternating voltage. ~230V

Question 8

what is the purpose of the neutral wire?

Answer 8

to complete the circuit with the live wire. 0V

Question 9

what is the purpose of the earth wire?

Answer 9

provides a low resistance path for electricity to prevent the case of the appliance from becoming live after an electrical fault. 0V

Question 10

what happens if you touch the live wire?

Answer 10

you die.
or get injured if you’re lucky

Question 11

how do electrical appliances transfer energy?

Answer 11

charge does work against resistance.

Question 12

what does high current produce?

Answer 12

high heat.

Question 13

what is the formula for energy transferred?

Answer 13

energy transferred jules = power watts x time seconds

Question 14

what is a power rating?

Answer 14

the amount of energy transferred per second.

Question 15

what is the formula for energy transferred using voltage?

Answer 15

energy transferred jules = charge flow coulombs x volts

Question 16

what happens when a charge goes through a change in voltage?

Answer 16

energy is transferred.

Question 17

what is the formula for power using volts?

Answer 17

power watts = volts x current amps

Question 18

what is the formula for power using resistance?

Answer 18

power watts = current² amps x resistance Ω

Question 19

what is the national grid?

Answer 19

a system of cables and transformers that connects power stations to consumer.

Question 20

why do power stations not run at maximum power?

Answer 20

so they can increase for high demand.

Question 21

why do power lines work at very high voltages?

Answer 21

to minimise energy lost by heating. from high current (P=IV)

Question 22

what is a transformer?

Answer 22

a device that increases or decreases the voltage of an ac.

Question 23

what does a step up transformer do?

Answer 23

increases the voltage and decreases the current.

Question 24

what does a step down transformer do?

Answer 24

decreases the voltage and increases the current.

Question 25

what is the formula for the voltage and current across a transformer?

Answer 25

**primary coil (voltage x current** *amps***)** **= secondary coil (voltage x current** *amps***)**

Question 26

what is static electricity?

Answer 26

charge which can not move.

Question 27

how is static electricity created?

Answer 27

when insulators are rubbed together electrons leave one and jump to the other leaving both materials electrically charged. *one positive and one negative*

Question 28

do electrons or protons move to cause static electricity?

Answer 28

only electrons move.

Question 29

when does static electricity spark?

Answer 29

when there is a high enough potential difference between a charged object and an earthed object.

Question 30

what is an electric field?

Answer 30

an area created around any electrically charged object where another charged object would experience a force.

Question 31

what happens to an electric field the closer you get to it?

Answer 31

the strength increases.