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year 10 > Topic 2 Electricity GCSE Physics > Flashcards

Topic 2 Electricity GCSE Physics Flashcards

1
Q

What is electric current?

A
  • flow of electric charge
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2
Q

When will electric charge flow around a complete circuit?

A
  • if there is a potential difference
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3
Q

What is the unit of current?

A
  • ampere
  • A
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4
Q

What is the current in a single/closed loop?

A
  • current has the same value everywhere in the circuit
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5
Q

What is potential difference?

A
  • driving force that pushes the charge around
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6
Q

What is the unit for potential difference?

A
  • volt
  • V
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7
Q

What is resistance?

A
  • anything that slows the flow down
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8
Q

What is the unit for resistance?

A
  • ohm
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9
Q

What does the current flowing through the component depend on?

A
  • the potential difference across it and the resistance of the component
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10
Q

A greater resistance means what for the current?

A
  • the greater the resistance across a component, the smaller the current that flows
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11
Q

What is the size of the current?

A
  • rate of flow of charge
  • more charged passes around the circuit when a larger current flows
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12
Q

What is the charge equation?

A

charge flow= current X time

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13
Q

LEARN CURRENT SYMBOLS

A

P 24

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14
Q

How do you calculate potential difference?

A

potential difference = current X resistance

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15
Q

How can you investigate the factors affecting resistance?

A

1- attach the crocodile clip to wire level with 0cm on the ruler
2- attach second crocodile clip to the wire (10cm away from the first clip)
3- close the switch then record the current and pd
4- open switch then move the second crocodile clip another 10 cm across the wire, close switch again and record current and pd
5- repeat for different lengths
6- work out resistance
- graph should be a straight line

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16
Q

What is an ammeter?

A
  • measures current (in amps)
  • ammeter must always be placed in series
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17
Q

What is a voltmeter?

A
  • measures the potential difference
  • must always be placed in parallel around whatever your in investigating
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18
Q

Does the resistance of ohmic conductors change with the current?

A
  • does not change with the current
  • at a constant temperature the current flowing through an ohmic conductor is directly proportional to the pd across it
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19
Q

What happens when an electric charge flows through a filament lamp?

A
  • it transfer some energy to the thermal energy store of the filament which is designed to heat up
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20
Q

For diodes, what does the resistance depend on?

A
  • depends on the direction of the current
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21
Q

look at bottom of p26

A

iv graphs!!

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22
Q

What is an LDR?

A
  • resistor that is dependent on the intensity of light
  • in bright light the resistance falls
  • in darkness the resistance is highest
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23
Q

What is a thermistor?

A
  • temperature dependent resistor
  • in hot conditions the resistance drops
  • in cool conditions the resistance goes up
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24
Q

What can sensing circuits be used to?

A
  • to turn on and increase the power to components depending on the conditions they are in
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25
Q

How are the different components connected in a series circuit?

A
  • in a line, end to end
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26
Q

In a series circuit, how is pd shared?

A
  • the total pd of the supply is shared between the various components
  • so the pd around a series circuit always adds up to the equal source pd

V total= V1 +V2 + ….

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27
Q

How is the current in a series circuit?

A
  • the same current flows through all components
  • the size of the current is determined by the total pd of cells and the total resistance of the circuit
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28
Q

How is the resistance in a series circuit?

A
  • the total resistance of two components is just the sum of their resistances
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29
Q

Why is the total resistance of two components the sum of their resistances?

A
  • because adding by resistor in series, the the two resistors have to share the total pd
30
Q

How is the pd across each resistor?

A
  • lower
  • so the current through each resistor is also lower
31
Q

How is the current in a series circuit?

A
  • same everywhere
  • so the total current in the circuit is reduced when a resistor is added
  • so total resistance of circuit increases
32
Q

How is each component connected in a parallel circuit?

A
  • separately connected to the +ve and -ve of the supply
33
Q

How is the potential difference in parallel circuits?

A
  • all components get the full source pd
  • so pd is the same across all components
    (so identical bulbs connected in parallel will be the same brightness)
34
Q

How is the current in a parallel circuit?

A
  • total current around the circuit is equal to the total of all the currents through the separate components
35
Q

How is the resistance in a parallel circuit?

A
  • if you have two resistors in parallel, their total resistance is less than the resistance of the smallest of the two resistors (look a bottom of p29)
36
Q

How can you investigate adding resistors in series?

A

look at p30

37
Q

What are the two types of electricity supply?

A
  • alternating current and direct current
38
Q

How is the current in alternating current supplies?

A
  • current is constantly changing direction
39
Q

What are alternating currents produced by?

A
  • by alternating voltages
  • in which the positive and negative ends keep alternating
40
Q

What is the ac supply of the uk mains?

A

230V

41
Q

What is the frequency of the ac mains supply?

A

50 cycles per second 50Hz

42
Q

What do cells and batteries supply?

A
  • direct current
43
Q

What is direct current?

A
  • a current that is always flowing in the same direction
  • created by direct voltage
44
Q

How are electrical appliances connected to the mains supply?

A
  • connected by three-core cables
  • they have three wires inside them (each with copper and coloured plastic coating)
45
Q

What is the live wire?

A
  • brown
  • provides an alternating potential difference (at about 230V) from the mains supply
46
Q

What is the neutral wire?

A
  • blue
  • completes the circuit
  • when the appliance is operating normally, current flows through the live and neutral wires
  • it is around 0V
47
Q

What is the earth wire?

A
  • green and yellow
  • protecting the wiring and for safety
  • stops the appliance casing from becoming live
  • does not carry a current (only when there’s a fault)
  • 0V
48
Q

What happens if you touch the live wire?

A
  • a large potential difference is produced across your body and a current flows through you
  • causing an electric shock
49
Q

Why does moving charge transfer energy?

A
  • charge does work against the resistance of the circuit
50
Q

How does the kettle transfer energy?

A
  • electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle
51
Q

How is energy transferred in a fan?

A
  • electrically from the battery of a hand held fan to the kinetic energy store of the fans motor
52
Q

What is the power of an appliance?

A
  • energy it transfers per second
  • so the more energy in a given time, the higher its power
53
Q

What is the energy transferred equation depending on power?

A

energy transferred= power X time

54
Q

What does the power rating tell you?

A
  • maximum amount of energy transferred between stores per second when the appliance is in use
55
Q

What happens when an electrical charge goes through a change in potential difference?

A
  • energy is transferred
56
Q

What is the energy transferred equation with pd?

A

energy transferred= charge flow X potential difference

57
Q

How can you calculate the power of an appliance?

A

power= potential difference X current

58
Q

What is the national grid?

A
  • giant system of cables and transformers that covers the UK and connects power stations to consumers
59
Q

What does the national grid transfer?

A
  • electrical power from power stations anywhere on the grid
60
Q

When does demand for electricity increase for the national grid?

A
  • predict when most electricity needs to be used
  • people getting up in the morning, people getting home from school/work
61
Q

What does the national grid use?

A
  • high potential difference or a high current
62
Q

What is the problem with high current with the national grid?

A
  • lose loads of energy as wires heat up and energy is transferred to the thermal energy stores of the surroundings
63
Q

For efficient transmission with the national grid what is used?

A
  • transformers
  • nearly 100% efficient
64
Q

What do transformers have?

A
  • have two coils ( a primary coil and a secondary coil joined with an iron core)
65
Q

Why is potential difference increased using a step-up-transformer?

A
  • more turns on the secondary coil than the primary coil
66
Q

What happens when certain insulating materials are rubbed together?

A
  • negatively charged electrons will be scraped off one and dumped on the other
  • leaving the materials electrically charged with static charge on one and an equal negative static charge on the other
67
Q

As an electric charge builds on an object what happens to the pd?

A
  • pd between the object and the earth (which is at 0V) increases
68
Q

In a static, what happens if the pd gets large enough?

A
  • electrons can jump across the gap between the charged object and the earth
  • this is the spark
69
Q

What happens when two electrically charged objects are brought close together?

A
  • exert a force on one another
70
Q

When is an electric field created?

A
  • around any electrically charged object
71
Q

What happens when a charged object is placed in the electric field of another object?

A
  • it feels a force
  • this force causes the attraction or repulsion
  • force caused by the electric fields of each charged object interacting
72
Q

When are sparks caused?

A
  • when there is a high enough pd between a charged object and the earth

year 10 (21 decks)

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