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Physics by Thaidz > Electricity > Flashcards

Electricity Flashcards

(77 cards)

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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
What is the unit for voltage ?
Volt
26
What is Resistance ? Unit?
anything in circuit which slows the flow down adding components will increase overall resistance Unit - Ohm Ω
27
What happens to the current when you increase the voltage ?
more current will flow
28
What happens to the current when you increase the resistance ?
less current will flow
29
What is an ammeter ? | How is it connected ?
measures current | always connected in series, never parallel
30
What is a voltmeter ? | How is it connected ?
measures voltage | always connected parallel to component
31
what are basic circuits used for ?
testing components and getting V-I graphs for them
32
positions of component, ammeter, variable resistor and voltmeter in circuits
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
what does a variable resistor do ?
alters the current flowing through the circuit
34
What voltage is UK mains electricity supply at?
230V
35
what is a.c. ?
alternating current, current is constantly changing direction
36
what is d.c. ?
direct current so current keeps flowing in the same direction
37
Mains supply is a.c. / d.c. ?
a.c.
38
Battery supply is a.c. / d.c. ?
d.c.
39
Voltage =
current x resistance
40
gradient of V-I graph =
1/Resistance
41
in V-I graph, steeper the gradient...
the lower the resistance
42
In V-I graph, straight line means ...
constant gradient, so constant resistance
43
What does LED stand for ?
Light-emitting diode
44
What does an LED do? | Uses? Advantages ?
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
Wire (V-I)
current through a wire is proportional to voltage
46
Metal filament lamp (V-I)
as temperature of metal filament increases, resistance also increases (creates curve)
47
Diode (V-I)
current only flows one direction
48
Resistor (V-I)
current through a resistor is proportional to voltage | different resistors have different resistances (different gradient)
49
What does LDR stand for?
light-dependant resistor
50
What is a LDR? | Uses ?
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
What is a Thermistor ? | Uses ?
temperature-dependant resistor hot conditions - low resistance cold conditions - high resistance used as temp detector (car engine temp sensor)
52
Describe a series circuit | Any uses ?
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
Describe the current in series circuit | Is there an equation ?
same current flows through all parts A1 = current at start (circuit) A2 = current at end (circuit) A1 = A2
54
Describe a parallel circuit | Uses ?
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
charge =
current x time
56
what is charge carried by in solid metal conductors ?
negatively charged electrons
57
bigger flow of current =
more charge
58
what is charged measured in ?
coulombs (C)
59
What is one volt the same as?
one joule per coulomb
60
What is voltage ?
the energy transferred per unit charge passed | also the driving force that pushes the current
61
what is the symbol for charge ?
Q
62
what happens when charge goes through a change in voltage?
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
what conducts charge?
materials that are electrical conductors - current can flow through easily (usually metals) e.g. silver Insulators don't conduct charge, e.g. plastic
64
How can you build up static ?
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
Describe polythene rod and duster rubbing
electrons move from duster to rod rod becomes negatively charged duster left with equal positive charge
66
Describe acetate rod and duster rubbing
electrons move from rod to duster rod left with equal positive charge duster becomes negatively charged
67
what is electrostatic charge caused by?
movement of electrons cause change of charge
68
How do you discharge a charged conductor safely ?
connect to earth with metal strap if charge is negative, electrons flow down strap if charge is positive, electrons flow up strap
69
what happens as charge builds up ?
voltage also build up, causing sparks
70
what do like charges do?
repel
71
what do opposite charges do ?
attract
72
Describe van de graaf generators
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
How do inkjet printers work ?
- 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
How do photocopiers work ?
- 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
How does clothing become static ? What happens ?
synthetic clothing dragged over each other becomes charged (electrons get scraped off) leads to attraction and little sparks / shocks as charges rearrange themselves
76
What causes lightning ?
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
What are the dangers of fuel-filling ? | What is the solution
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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