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Physics by Thaidz > Electricity > Flashcards

Electricity Flashcards

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1
Q

State the metal parts in plugs and why they are used

A

brass and copper as they are very conductive

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2
Q

State the casing in plugs and why they are used

A

rubber or plastic as they are insulators (prevents shocks) and flexible

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3
Q

what is the colour of live wire?

A

brown

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4
Q

what is the colour of earth wire?

A

green/yellow

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5
Q

what is the colour of neutral wire?

A

blue

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6
Q

state the use of live wire

A

carries current to the appliance at a high voltage (about 230 V)

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7
Q

state the use of neutral wire

A

completes the circuit and carries current away from the appliance (always at 0 V)

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8
Q

what is meant by double insulated ?

A

doesn’t need an earth wire as no metal parts are showing so you can’t get a shock

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9
Q

what are some safety precautions for plugs ?

A

make sure live parts aren’t exposed (or you could get shocked)
no water near electrical objects

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10
Q

what happens when the live wire inside an appliance comes loose and touches the metal casing?

A

the current goes through the earth wire down to the earth instead of shocking you

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11
Q

what does a fuse / circuit breaker do?

A

cuts off the live supply (current) stopping shocks / fires

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12
Q

what are the advantages of circuit breakers ?

A

break the circuit by opening a switch
can be reset easily, fuses must be replaced once melted
operates faster than fuses and detects small current changes

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13
Q

what does RCCB stand for?

A

residual current circuit breaker

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14
Q

what does a RCCB do?

A

if you touch the live, less current goes to the neutral

The RCCB detects the change and quickly cuts off the power by opening a switch

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15
Q

what happens when there is an electrical current in a resistor ?

A

its heats up
heat effect increases resistance so less current flows
heat effect can cause components to melt (fuse)

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16
Q

state the uses of electrical current in resistors

A

fuses (safety)
toasters - has a coil of wire with high resistance so when current flows it heats up and glows which gives off infrared radiation (cooks bread)

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17
Q

What is electrical power measured in ?

A

watts (W)

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18
Q

(electrical) power =

A

current x voltage (I x V)

P on the IVy

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19
Q

Energy (transferred) =

A

current x voltage x time

E on the IVT

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20
Q

1000W =

A

1kW

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21
Q

If an appliance is using 4.3 Amps, what fuse should be used?

A

5 Amp fuse as it should withstand a little higher current

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22
Q

Unit for energy

A

J

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23
Q

what does current give off

A

heat

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24
Q

What is current ? Unit ? Anything else?

A

rate of flow of electrical charge round the circuit
only flows if there is a voltage
FLOWS +VE TO -VE
Unit - Amp

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25
Q

What is the unit for voltage ?

A

Volt

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26
Q

What is Resistance ? Unit?

A

anything in circuit which slows the flow down
adding components will increase overall resistance
Unit - Ohm Ω

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27
Q

What happens to the current when you increase the voltage ?

A

more current will flow

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28
Q

What happens to the current when you increase the resistance ?

A

less current will flow

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29
Q

What is an ammeter ?

How is it connected ?

A

measures current

always connected in series, never parallel

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30
Q

What is a voltmeter ?

How is it connected ?

A

measures voltage

always connected parallel to component

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31
Q

what are basic circuits used for ?

A

testing components and getting V-I graphs for them

32
Q

positions of component, ammeter, variable resistor and voltmeter in circuits

A

component, variable resistor and ammeter all in series so can be in any order in main circuit
voltmeter must be parallel and around component

33
Q

what does a variable resistor do ?

A

alters the current flowing through the circuit

34
Q

What voltage is UK mains electricity supply at?

A

230V

35
Q

what is a.c. ?

A

alternating current, current is constantly changing direction

36
Q

what is d.c. ?

A

direct current so current keeps flowing in the same direction

37
Q

Mains supply is a.c. / d.c. ?

A

a.c.

38
Q

Battery supply is a.c. / d.c. ?

A

d.c.

39
Q

Voltage =

A

current x resistance

40
Q

gradient of V-I graph =

A

1/Resistance

41
Q

in V-I graph, steeper the gradient…

A

the lower the resistance

42
Q

In V-I graph, straight line means …

A

constant gradient, so constant resistance

43
Q

What does LED stand for ?

A

Light-emitting diode

44
Q

What does an LED do?

Uses? Advantages ?

A

emit light when current flows in forward direction
no filament so don’t burn out
used in digital clocks, traffic lights and remotes
indicate presence of current, used to show its on

45
Q

Wire (V-I)

A

current through a wire is proportional to voltage

46
Q

Metal filament lamp (V-I)

A

as temperature of metal filament increases, resistance also increases (creates curve)

47
Q

Diode (V-I)

A

current only flows one direction

48
Q

Resistor (V-I)

A

current through a resistor is proportional to voltage

different resistors have different resistances (different gradient)

49
Q

What does LDR stand for?

A

light-dependant resistor

50
Q

What is a LDR?

Uses ?

A

resistor that changes its resistance depending on how much light falls on it
bright light - low resistance
darkness - resistance at highest
used for electronic circuits e.g. burglar detectors

51
Q

What is a Thermistor ?

Uses ?

A

temperature-dependant resistor
hot conditions - low resistance
cold conditions - high resistance
used as temp detector (car engine temp sensor)

52
Q

Describe a series circuit

Any uses ?

A

components connected in a line, end to end
can’t switch one off (breaks circuit), either all on or off
more components used = more resistance
not used often… like fairy lights

53
Q

Describe the current in series circuit

Is there an equation ?

A

same current flows through all parts
A1 = current at start (circuit)
A2 = current at end (circuit)
A1 = A2

54
Q

Describe a parallel circuit

Uses ?

A

each component separately connected
disconnect/switch off one will not affect others
each component has its own loop
used in household lights (can be turned on and off)

55
Q

charge =

A

current x time

56
Q

what is charge carried by in solid metal conductors ?

A

negatively charged electrons

57
Q

bigger flow of current =

A

more charge

58
Q

what is charged measured in ?

A

coulombs (C)

59
Q

What is one volt the same as?

A

one joule per coulomb

60
Q

What is voltage ?

A

the energy transferred per unit charge passed

also the driving force that pushes the current

61
Q

what is the symbol for charge ?

A

Q

62
Q

what happens when charge goes through a change in voltage?

A

energy is transferred
energy supplied to charge at power source
charge gives up energy at voltage drop in components
as voltage increases, so does energy transferred

63
Q

what conducts charge?

A

materials that are electrical conductors - current can flow through easily (usually metals) e.g. silver
Insulators don’t conduct charge, e.g. plastic

64
Q

How can you build up static ?

A

caused by friction
rubbing two insulating materials, electrons will move to one, leaving a positive electrostatic charge on one, and negative on the other (depends on material)
electrically charged objects attract smaller objects

65
Q

Describe polythene rod and duster rubbing

A

electrons move from duster to rod
rod becomes negatively charged
duster left with equal positive charge

66
Q

Describe acetate rod and duster rubbing

A

electrons move from rod to duster
rod left with equal positive charge
duster becomes negatively charged

67
Q

what is electrostatic charge caused by?

A

movement of electrons cause change of charge

68
Q

How do you discharge a charged conductor safely ?

A

connect to earth with metal strap
if charge is negative, electrons flow down strap
if charge is positive, electrons flow up strap

69
Q

what happens as charge builds up ?

A

voltage also build up, causing sparks

70
Q

what do like charges do?

A

repel

71
Q

what do opposite charges do ?

A

attract

72
Q

Describe van de graaf generators

A

used to demonstrate electrostatic charges
made of rubber belt moving round plastic rollers under metal dome
stand on insulated chair and touch charged dome and charge will flow through you

73
Q

How do inkjet printers work ?

A
  • tiny ink drops forced out fine nozzle (gives charge)
  • drops deflected as passed between 2 metal plates, voltage applied on plates, one -ve, one +ve
  • drops attracted to opposite charge, repel like charge
  • size/direction of voltage changes so each drop lands in a different place on paper
  • loads of tiny dots make up printout
74
Q

How do photocopiers work ?

A
  • image plate is +ve charged, image projected onto it
  • white parts of image make light fall on it, charge leaks away from these parts
  • charged parts (darker) attract negatively charged black powder onto positive paper
  • paper heated so powder sticks
75
Q

How does clothing become static ? What happens ?

A

synthetic clothing dragged over each other becomes charged (electrons get scraped off)
leads to attraction and little sparks / shocks as charges rearrange themselves

76
Q

What causes lightning ?

A

rain drops and ice bump together in storm clouds
knocks electrons off, leaving top of cloud +ve and bottom -ve
causes huge voltage and big spark

77
Q

What are the dangers of fuel-filling ?

What is the solution

A

as fuel flows out filler pipe, static can build up
can lead to spark, causing explosion (fuel)
solution : make nozzle metal so charge conducted away and add earth strap between tank and pipe

Physics by Thaidz (7 decks)

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