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physics p1 > electricity p2 > Flashcards

electricity p2 Flashcards

1
Q
A
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2
Q

what is the definition of electric current

A

flow of electrons around a circut

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3
Q

what happenes when current passes a light in a circuit

A

the electrical energy is transferred to light energy and thermal energy

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4
Q

what’s the unit for current?

A

amps

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5
Q

how do we measure the current in a circuit?

A

ammeter

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6
Q

what happenes to current in a parallel circuit

A

current splits and each branch adds up to the total leaving the cell

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7
Q

what is potential difference measured in?

A

volts

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8
Q

how do we measure potential difference?

A

voltmeter

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9
Q

how do you have to place a voltmeter in a circuit

A

in parallel

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10
Q

what happenes to potential difference in a series circuit?

A

it splits between the components

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11
Q

what happenes to potential difference in a parallel circuit?

A

stays the same across componants

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12
Q

what happens to potential difference when you add another cell and make a battery

A

potential difference doubles

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13
Q

what does resistance tell us?

A

the potential difference needed to drive a current through a component

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14
Q

what is a factor affecting whether a resistor is constant

A

temperature

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15
Q

is a filiment lamp an ohmic conductor?

A

no as the temperature increases

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16
Q

what is the relationship between current and potential difference through a resistor

A

directly proportional

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17
Q

key features of a diode?

A

current only flows in one direction
very high resistance in the reverse direction

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18
Q

what is a diode useful for

A

controlling the flow of current in a circuit

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19
Q

what happens to resistors in series

A

total resistance is added together

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20
Q

what happens to resistors in parallel?

A

total resistance of two resistance is smaller than the smallest individual resistor

21
Q

why is the total resistance smaller in parallel?

A

the current has at least two different pathways

22
Q

what happens to the resistance in LDR in different lighting conditions

A

dark = high resistance
light = low resistance

23
Q

when are LDRs used irl

A
  • when you are on a phone call and hold phone to ur ear the screen switches off to save battery
  • lights which turn on automatically in the dark
24
Q

what happens in a thermistor?

A

resistance decreases when temperature increases

25
Q

uses of thermistor irl

A

cooling fan in computers- when they reach a certain temperature the resistance will decrease and the cooling fan will come on to decrease the temperature

26
Q

what is the energy transfer in fans and blenders?

A

electrical energy is transferred to kinetic energy of electric motors
(+thermal energy due to friction)

27
Q

what is the energy transfer in irons and kettles?

A

electrical energy is transferred to thermal energy

28
Q

what is the energy transfer in hair dryers and washing machines

A

transferred into kinetic and thermal energy

29
Q

what is the definition for power?

A

the rate at which energy is transferred

30
Q

what is the unit for power?

A

watts

31
Q

what type of current is current from a cell

A

direct current

32
Q

what type of current is mains electricity?

A

alternating current

33
Q

what is the benefit of an alternating current?

A

very easy to use a transformer to increase or decrease the potential difference

34
Q

what does alternating current mean?

A

current flows in forward and reverse directions

35
Q

what are the three types of wire in a plug?

A

brown
blue
green/yellow

36
Q

what is the brown wire

A

live wire
carries alternating potential difference from supply
connected to a fuse the plug
extremely dangerous

37
Q

what is the blue wire

A

neutral
completes the circuit
potential difference = 0V

38
Q

what is the green/yellow wire

A

earth wire
safety wire to stop the wire becoming live

39
Q

why is the earth wire important

A

if it becomes live huge current flows to the earth. the fuse melts and shuts off the current. prevents anyone from getting an electric shock

40
Q

what does the national grid consist of?

A

system of transformers and high voltage cables

41
Q

what does a step up transformer do?

A

increases potential difference

42
Q

why are step up transformes important

A

less energy is lost when there is a higher potential difference

43
Q

what does a step down transformer do?

A

reduce potential difference to around 230V

44
Q

example of a good conductor

A

metal

45
Q

why are metals good conductors?

A

electrons can easily flow through

46
Q

what happens when certain insulating materials are rubbed against each other

A

they become electrically charged
Negatively charged electrons are rubbed off one material and on to the other.
The material that gains electrons becomes negatively charged.
The material that loses electrons is left with an equal positive charge.

47
Q

what is force of attraction

A

two opposite charges

48
Q

what is force of repulsion

A

two of the same charges

49
Q

how are field lines shown

A

perpendicular to object
90˚ angle

physics p1 (11 decks)

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