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physics > P4,5 Electricity > Flashcards

P4,5 Electricity Flashcards

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1
Q

What is current?

A

The flow of electral charge

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2
Q

What can electric charge only flow around?

A

A closed system (completed system)

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3
Q

What is another way of saying voltage?

A

Potential difference

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4
Q

What pushes the electrons around a circut?

A

Voltage/potential difference

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5
Q

What is resistance measured in?

A

Ohms (alphs symbol)

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6
Q

The greater the resistance the …

A

Smaller the currnet

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7
Q

What does the current flowing through a component depend on”

A

The voltage and the resistance

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8
Q

What dies the total charge theoigh a circut depend on?

A

Current and time

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9
Q

What is current?

A

The rate of flow of charge

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10
Q

Q=IT what does Q mean?

A

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

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11
Q

What is charge measured in?

A

Couloms

C

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12
Q

What is currne measured in?

A

A

Amps

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13
Q

What is an ohmic conductor?

A

An conductor that has a constat resiatance

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14
Q

Give an example of a component that is non ohmic?

A

Doide or lamp

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15
Q

What does LRD stand for?

A

Light Dependent Resistor

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16
Q

What is a LDR?

A

A resistor that depends on light intensity

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17
Q

How does an LDR react to light?

A

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

Darkness the resitance is higher

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18
Q

What may an LDR be used for?

A

Night loghts

Burgerler detenction

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19
Q

What does a thermestor depend on?

A

Temprature

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20
Q

How does a thermistor react to heat?

A

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

Cool condition the resistance increases

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21
Q

What may a thermistor be used for?

A

Car wngine temprature sensors

Electronic thermostats

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22
Q

What can sensing circutes be used for?

A

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

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23
Q

How may a thermistor control a fan?

A

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

24
Q

What tyoe of electricity comes from the mains?

A

(Pur plugs/walls)

ac

25
Q

What type of electricity comes from bateries?

A

dc

26
Q

What does ac stand for?

A

Alternating currents

27
Q

What does dc stand for?

A

Direct current

28
Q

Describe ac supply?

A

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

29
Q

What is the mains supply in the UK?

A

230V

30
Q

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

A

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

50Hz

31
Q

Describe dc?

A

From a battery

Same direction and is created by a direct voltage

32
Q

What are the 3 types of wires in a cable?

A 
Live wire (brown)
Neutral wire (blue)
Earth wire (green and yellow)
33
Q

What does the live wire do?

A

Provides an alternating curent (230V)

Is brown

34
Q

What does the neutral wire do?

A

It completes the circut
Around 0V
Blue

35
Q

What does the earth wire do?

A

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

36
Q

What V is your body at?

A

0V

37
Q

Why does an electric shock happen?

A

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

38
Q

Why are electric shocks so dangerous?

A

Even if the applience/ wire is off it could still carry a pd

There is a low resistance path between you and the wire

39
Q

Why is moving a charge a type of energy?

A

The electorns are doing work against the resistance

40
Q

What is the power rating?

A

The maximum safe power which the thing can operate at

41
Q

What may a power rating do?

A

Help the customer choose which appliance to buy

42
Q

What is voltage?

A

Energy transfered per charge passed

43
Q

What is charge flow measured in?

A

Coublums

C

44
Q

What is potential difference measured in?

A

Volts

45
Q

How is energy distributed?

A

The national grid

46
Q

What is the national grid?

A

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

47
Q

Hwo do power stations predict demand for energy?

A

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

48
Q

Why do power stations normally run below maximim power output?

A

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

49
Q

Pd means what?

A

Potential difference

Voltage

50
Q

Hoe does the national grid transfer energy?

A

Using set up and step down transformers

51
Q

What dies a strp up transformer do?

A

It decreased the current and increases the voltage

52
Q

Why is higher voltages used to transfer energy?

A

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

53
Q

At what voltage is energy transfered at?

A

400,000V

54
Q

What is a pylon?

A

One of those towers that hold up the power lines

55
Q

How efficent are transformers?

A

Almost 100%

physics (11 decks)

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