2 ELECTRICITY Flashcards

1
Q

Unit for current

A

Ampere (A)

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2
Q

Unit for charge

A

Coulomb (C)

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3
Q

Unit for energy

A

Joule (J)

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4
Q

Unit for resistance

A

Ohm ( X )

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5
Q

Unit for time

A

Second (s)

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6
Q

Unit for voltage

A

(V)

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7
Q

Unit for power

A

Watt (W)

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8
Q

Dangers of electricity

A
  1. Electric Shocks
  2. Electrical fires
  3. Damage appliances
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9
Q

How does insulation protect the user?

A
  • Plastic coating covers the wires, so no current flows, as plastic is an insulator
  • If someone touches it, they don’t get shocked and prevents short circuits
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10
Q

How does double insulation protect the user?

A
  • Appliances with a plastic case and insulated wires
  • If a fault occurs inside, there is no orute for the current to take, so no risk of shock
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11
Q

How do fuses protect the user?

A
  • A thin wire in a ceramic case, when current flows through, it heats up
  • When current is too high, the wire melts and is ‘blown’
  • Breaks the curcuit, os the user is safe, a nd appliance undamaged
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12
Q

How does an earth wire protect user?

A
  • Appliances in metal cases are earthed, and the earth wires connect to the case
  • If the live wire cones loose and touches the case, you are at risk of shock
  • Earth wire provides a lower resistance route for current, so current flows thorugh the earth wire, not the user
  • As resistance is low, a high current flows which breaks the fuse
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13
Q

Advantages of circuit breakers over fuses

A
  • Can be reset - use magnets not wires
  • Act quicker than fuses
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14
Q

Charge equation

A

Charge = current x time

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15
Q

Charge symbol equation

A

Q = It

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16
Q

What is potential differance

A

Voltage

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17
Q

Voltage equation

A

Voltage = Current x Resistance

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18
Q

Voltage symbol equation

A

V = IR

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19
Q

What is a volt

A

Joule per coulomb (J/C)

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20
Q

Define current

A

The rate of flow of charge

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21
Q

Define voltage

A

The energy transferred per unit charge passed

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22
Q

Energy equation (charge)

A

Energy = charge x time

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23
Q

Energy equation (triple)

A

Energy = current x time x voltage

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24
Q

Energy equation (charge) symbol

A

E = Qt

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25
Q

Energy equation (triple) symbol

A

E = IVt

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26
Q

Direction of A.C

A

Constantly changing

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27
Q

Voltage of A.C

A

Mains electricity - 230V

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28
Q

Direction of D.C

A

Current only flows one way (conventional)

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29
Q

Voltage of D.C

A

Low voltage - Batteries and cells

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30
Q

Power equation

A

Power = Current x Voltage

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31
Q

Power equation symbol

A

P = IV

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32
Q

Define power

A

The rate at which electrical energy is transferred

33
Q

Series circuit:
* Current
* Voltage
* Advantage
* Disadvantage

A
  • Same everywhere
  • Split between components
  • Longer battery life (Current is lower)
  • All off or all out (all bulbs are connected so go out)
34
Q

Parallel circuit:
* Current
* Voltage
* Advantage
* Disadvantage

A
  • Splits between branches
  • Same everywhere
  • Switch on/off seperately
  • Shorter battery life
35
Q

Does a resistor obey ohm’s law

A

Yes - Straight line through origin

36
Q

Does a filament lamp obey ohm’s law

A

No

37
Q

Does a diode obey ohm’s law

A

No

38
Q

Reistor, filament lamp, diode - Which way does it conduct

A

Diode only conducts one way (others both ways)

39
Q

Describe a resistor IV graph

A

I directly proportional to V - straight line through origin

40
Q

Describe a filament lamp IV graph

A

As voltage increases, current levels off

41
Q

Describe a diode IV graph

A

Sharp increase of current, as voltage increases

42
Q

What direction is convetional current

A

Positive to negative

43
Q

What way do electrons flow

A

Opposite to conventional current

44
Q

Why can a metal wire conduct electricity

A

The negatively charged electrons are free to move around the metal

45
Q

Why do wire heat up, and bulb IV graphs level off?

A
  • As V increases, R increases, I levels off (V=IR)
  • The bulb/wire gets hot, and particles in the bulb/wire vibrate more
  • This causes more collisons of particles
  • So a higher resistance
  • Longer wire = more current = more resistance
46
Q

Does a thermistor obey ohm’s law

A

No - As temperature increases, resistance decreases

47
Q

Does a LDR obey ohm’s law

A

No - as light intensity increases, resistance decreases

48
Q

How must you connect an ammeter

A

In series

49
Q

How must you connect a voltemeter

A

In parallel

50
Q

Double insulated symbol

A
51
Q

Battery symbol

A
52
Q

Voltmeter symbol

A
53
Q

Ammeter symbol

A
54
Q

Fuse symbol

A
55
Q

LED symbol

A
56
Q

Diode symbol

A
57
Q

LDR symbol

A
58
Q

Resistor symbol

A
59
Q

Thermistor symbol

A
60
Q

Variable resistor symbol

A
61
Q

Common insulators

A

Wood, plastic and glass

62
Q

Conductor example

A

Metal

63
Q

What materials can build up electrostatic charge

A

Only insulators

64
Q

How to show electrostatic charge with paper

A
  • Rub a polythene rod with a duster and hold by pieces of paper
  • Electron transfer from duster to rod
  • Rod is negatively charged
  • Paper stick to rod as attracted
65
Q

How to show electrostatic charge by suspended rods

A
  • Charge a polythene rod by friction and suspend it upside down
  • Electron transfer from duster to rod
  • Charge an acetate/polythene rod by friction and suspend next to but not touching other rod
  • Like charges repel
  • Opposite charges attract
66
Q

Dangers and soloutions to electrostatically refuelling an aircraft

A
  • Body becomes electrostatically charged during flight, as air rubs on fueslarge
  • Can cause a spark and explosion
  • Earth the aircraft with an earth wire so there is no build up of charge
  • No risk of spark or explosion
67
Q

How do positive and negative electrostatic charges occur

A

Transfer of electrons

68
Q

How does electrostatic paint spraying occur, and what are it’s advantages

A
  • Nozzle has positive charge
  • Object has negative charge
  • Positive paint droplets repel and spread out
  • So you get an even coat
  • Positive is attracted to negative, so no paint is wasted as it covers all sides
69
Q

Colour of live wire

A

Brown

70
Q

Colour of neutral wire

A

Blue

71
Q

Colour of earth wire

A

Green / Yellow

72
Q

Job of live wire

A

High energy

73
Q

Job of neutral wire

A

Complete the circuit (return wire)

74
Q

Job of earth wire

A

Safety

75
Q

What side of the plug is the neutral wire

A

Left

76
Q

What side of the plug is the live wire

A

Right

77
Q

When is an earth wire needed

A

If the appliance is not double insulated

78
Q

How to show electrostatic charge by suspended rods

A
  • Charge a polythene rod by friction and suspend it upside down
  • Electron transfer from duster to rod
  • Charge an acetate/polythene rod by friction and suspend next to but not touching other rod
  • Like charges repel
  • Opposite charges attract
79
Q

How must you connect an ammeter

A

In series