P4,5 Electricity

Question 1

What is current?

Answer 1

The flow of electral charge

Question 2

What can electric charge only flow around?

Answer 2

A closed system (completed system)

Question 3

What is another way of saying voltage?

Answer 3

Potential difference

Question 4

What pushes the electrons around a circut?

Answer 4

Voltage/potential difference

Question 5

What is resistance measured in?

Answer 5

Ohms (alphs symbol)

Question 6

The greater the resistance the …

Answer 6

Smaller the currnet

Question 7

What does the current flowing through a component depend on”

Answer 7

The voltage and the resistance

Question 8

What dies the total charge theoigh a circut depend on?

Answer 8

Current and time

Question 9

What is current?

Answer 9

The rate of flow of charge

Question 10

Q=IT what does Q mean?

Answer 10

The current flowing past a point in for a certian length of time

Question 11

What is charge measured in?

Answer 11

Couloms

C

Question 12

What is currne measured in?

Answer 12

A

Amps

Question 13

What is an ohmic conductor?

Answer 13

An conductor that has a constat resiatance

Question 14

Give an example of a component that is non ohmic?

Answer 14

Doide or lamp

Question 15

What does LRD stand for?

Answer 15

Light Dependent Resistor

Question 16

What is a LDR?

Answer 16

A resistor that depends on light intensity

Question 17

How does an LDR react to light?

Answer 17

Bright light the resitance falls (easier for charge to put throuhg)

Darkness the resitance is higher

Question 18

What may an LDR be used for?

Answer 18

Night loghts

Burgerler detenction

Question 19

What does a thermestor depend on?

Answer 19

Temprature

Question 20

How does a thermistor react to heat?

Answer 20

Hot conditions the resistance drops (easier to charge to flow)

Cool condition the resistance increases

Question 21

What may a thermistor be used for?

Answer 21

Car wngine temprature sensors

Electronic thermostats

Question 22

What can sensing circutes be used for?

Answer 22

Turning on or increasing the power to components depending on conditions that they are in

Question 23

How may a thermistor control a fan?

Answer 23

As it gets hotter the resistance is decreased by the thermistor: this causes the fan to go faster as more voltage

Question 24

What tyoe of electricity comes from the mains?

Answer 24

(Pur plugs/walls)

ac

Question 25

What type of electricity comes from bateries?

Answer 25

dc

Question 26

What does ac stand for?

Answer 26

Alternating currents

Question 27

What does dc stand for?

Answer 27

Direct current

Question 28

Describe ac supply?

Answer 28

The current is constantly changing direction (between positive and negative)

Question 29

What is the mains supply in the UK?

Answer 29

230V

Question 30

What is the frequency of the mains ac supply in the UK?

Answer 30

50 cycles per second - (cycle = changing between positive and negative) 50Hz

Question 31

Describe dc?

Answer 31

From a battery Same direction and is created by a direct voltage

Question 32

What are the 3 types of wires in a cable?

Answer 32

``` Live wire (brown) Neutral wire (blue) Earth wire (green and yellow) ```

Question 33

What does the live wire do?

Answer 33

Provides an alternating curent (230V) Is brown

Question 34

What does the neutral wire do?

Answer 34

It completes the circut Around 0V Blue

Question 35

What does the earth wire do?

Answer 35

Protects the wires and is for saftey It stops the appliance from becoming live Only carries a current when there is a vault Green and yellow

Question 36

What V is your body at?

Answer 36

0V

Question 37

Why does an electric shock happen?

Answer 37

When you touch a live wire a large current goes into you as your body is at 0V

Question 38

Why are electric shocks so dangerous?

Answer 38

Even if the applience/ wire is off it could still carry a pd There is a low resistance path between you and the wire

Question 39

Why is moving a charge a type of energy?

Answer 39

The electorns are doing work against the resistance

Question 40

What is the power rating?

Answer 40

The maximum safe power which the thing can operate at

Question 41

What may a power rating do?

Answer 41

Help the customer choose which appliance to buy

Question 42

What is voltage?

Answer 42

Energy transfered per charge passed

Question 43

What is charge flow measured in?

Answer 43

Coublums C

Question 44

What is potential difference measured in?

Answer 44

Volts

Question 45

How is energy distributed?

Answer 45

The national grid

Question 46

What is the national grid?

Answer 46

System of cables ect which connects power stations to houses ect for energy

Question 47

Hwo do power stations predict demand for energy?

Answer 47

Time of day Kids coming home from school Big wvents such as world cup finals

Question 48

Why do power stations normally run below maximim power output?

Answer 48

So there is space to prosuce more is there is a surge in demand

Question 49

Pd means what?

Answer 49

Potential difference Voltage

Question 50

Hoe does the national grid transfer energy?

Answer 50

Using set up and step down transformers

Question 51

What dies a strp up transformer do?

Answer 51

It decreased the current and increases the voltage

Question 52

Why is higher voltages used to transfer energy?

Answer 52

So less energy is lost through thermal energy being transfered to its surroundings

Question 53

At what voltage is energy transfered at?

Answer 53

400,000V

Question 54

What is a pylon?

Answer 54

One of those towers that hold up the power lines

Question 55

How efficent are transformers?

Answer 55

Almost 100%