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Physics > Topic 2: Electricity > Flashcards

Topic 2: Electricity Flashcards

1
Q

What are the three wires in a plug?

A

live, neutral, earth

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2
Q

What voltage is the neutral wire?

A

0V

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3
Q

What is the purpose of an earth wire?

A

for safety - reduce danger of electric shock

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4
Q

Why are wires covered in plastic casing?

A

plastic acts as an insulator so prevents you from getting an electric shock

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5
Q

How does a fuse work?

A

if there is a big surge in current, the fuse ‘blows’ (melts) which cuts off the live supply

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6
Q

Why do we need a fuse?

A

it isolated the appliance and makes an electric shock impossible and prevents risk of fire

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7
Q

What wire in a plug is connected to the fuse?

A

live wire

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8
Q

What are the advantages of a circuit breaker?

A

-they can be easily reset
-much faster than fuses (safer)
-can detect smaller current changes

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9
Q

What is the difference between AC and DC current?

A

AC: mains electricity, current constantly changing direction
DC: batteries and cells, current always in same direction

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10
Q

What happens when an electric current is in a resistor?

A

energy transfer - heats up the resistor

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11
Q

Why does a resistor heat up?

A

electrons collide with the ions that make up the resistor - giving the ions more energy

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12
Q

How does heating effect a resistor?

A

increases the resistance - less current will flow

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13
Q

How does heating effect a circuit?

A

components melt - circuit will stop working

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14
Q

What is current?

A

rate of flow of charge

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15
Q

Current is proportional to…

A

voltage

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16
Q

(resistance) As the temperature of a metal filament increases….

A

resistance increases

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17
Q

Current will only flow through a diode in one…

A

direction

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18
Q

What does I stand for in Q=It?

A

current

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19
Q

What does Q stand for in Q=It?

A

charge

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20
Q

Voltage, current and resistance equation

A

Voltage = current x resistance

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21
Q

The steeper a voltage/ current graph the…

A

lower the resistance

22
Q

If the voltage/ current graph shows a curve, it means that…

A

the resistance is changing

23
Q

LDR: in bright light the resistance…

A

decreases

24
Q

LDR: in dark light the resistance….

A

increases

25
Q

What is a use of an LDR?

A

burglar detectors

26
Q

Thermistor: in hot conditions the resistance…

A

decreases

27
Q

Thermistor: in cold conditions the resistance…

A

increases

28
Q

What is a use of a thermistor?

A

car engine temperature detector sensors

29
Q

Why are light-emitting diodes useful?

A

emit light when current flows through them in the forward direction

30
Q

What are 2 uses of light-emitting diodes?

A

-traffic lights
-remote controls

31
Q

What is the total resistance in a series circuit?

A

total resistance of resistance of each component in the circuit

32
Q

Why does a resistor heat up?

A

electrons collide with the ions in the resistor lattice - releasing energy

32
Q

Example of an appliance with high resistance

A

toaster - coils of wire give off infrared radiation

32
Q

What is electrical power?

A

the rate at which an appliance transfers energy

33
Q

What is power measured in?

A

Watts (W)

34
Q

Electrical power, current and voltage equation

A

power = current x voltage

35
Q

What should fuses current ratings be?

A

just higher than the operating current

36
Q

Energy, current, voltage and time equation

A

energy = current x voltage x time

37
Q

Charge, current and time equation

A

charge = current x time

38
Q

When charge goes through a change in voltage, then…

A

energy is transferred

39
Q

The bigger the change in voltage, the more…

A

energy is transferred

40
Q

A battery with a bigger voltage will provide more…

A

energy for the circuit

41
Q

What is voltage?

A

the energy transferred per unit charge passed

42
Q

One volt =

A

one joule per coulomb

43
Q

Energy transferred, voltage and charge equation

A

energy = charge x voltage

44
Q

Energy transferred, charge, current and resistance equation

A

energy = charge x current x resistance

45
Q

How does a photocopier work using electrostatics?

A

-image plate/drum is positively charged
-white paper reflects light making the white areas of the drum leak away
-negatively charged toner is attracted to the positively charged image

46
Q

How does an inkjet printer work using electrostatics?

A

-ink negative charge
-two metal plates surrounding ink are oppositely charged
-ink repels from negative plate onto positive plate

47
Q

How does lightning form?

A

-air particles rub against each other
-charge build up in clouds
-build up discharges between the ground and the cloud
-stream of electrons which can cause fires

48
Q

How does an aircraft become electrically charged?

A

-air rubbing against aircraft (friciton)
-can cause a spark

49
Q

What is double insulation?

A

appliance made of plastic casing

Physics (10 decks)

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