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GCSE Physics > Section 5: Electricity & Circuits > Flashcards

Section 5: Electricity & Circuits Flashcards

1
Q

What is electric current?

A

The rate of flow of charge

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2
Q

What allows current to pass through metals?

A

Delocalised electrons

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3
Q

What happens to current if there is no source of potential difference?

A

No current flows

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4
Q

What happens to current if there is a source of potential difference?

A

Current flows

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5
Q

What is resistance?

A

Anything that slows down the flow of charge

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6
Q

What does current through a component depend on?

A

The components resistance and potential difference across the component

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7
Q

What happens to current if resistance increases?

A

The greater the resistance, the smaller the current

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8
Q

What can be used to change the current in a circuit?

A

Variable resistor

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9
Q

What is potential difference?

A

The energy transferred per unit of charge that passes between two points in a circuit

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10
Q

What is another name for potential difference?

A

Voltage

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11
Q

What is the unit of measure for charge?

A

Coulombs, C

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12
Q

What is the unit of measure for current?

A

Amperes, A

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13
Q

What is the unit of measure for resistance?

A

Ohms, Ω

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14
Q

What is the unit of measure for potential difference?

A

Volts, V

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15
Q

What is 1 volt equal to?

A

1 J/C OR 1 joule per coulomb

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16
Q

What happens to current in an open switch?

A

Current doesn’t flow

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17
Q

What happens to current in a closed switch?

A

Current flows

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18
Q

What are the three different current-potential difference graphs?

A
  1. Fixed resistor at a constant temp
  2. Filament lamp
  3. Diode
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19
Q

What happens in a fixed resistor at a constant temperature graph?

A

Current is directly proportional to potential difference SO resistance doesn’t change

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20
Q

What type of graph is the fixed resistor at a constant temperature graph?

A

Linear
(Straight line going through origin)

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21
Q

What happens in a filament lamp graph?

A

Current increases SO temperature of filament increases SO resistance increases

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22
Q

What does a filament lamp graph look like?

A

Non linear
Plateaus at bottom and top but straight line in the middle

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23
Q

What happens in a diode graph?

A

High resistance in one direction SO current only flows in the other direction

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24
Q

What does a diode graph look like?

A

Non linear
Line starts straight then its gradient rapidly increases

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25
Q

What components are the ones with a changing resistance when current through them varies?

A

Filament lamp
Diode
LDR (light dependent resistor)
Thermistor

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26
Q

CIRCUIT SYMBOLS MADE ON IN PERSON FLASHCARDS

A
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27
Q

What does resistance depend on in a LDR (light dependent resistor)?

A

Light intensity

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28
Q

When in there lower resistance in a LDR (light dependent resistor)?

A

When there’s a brighter light

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29
Q

When in there higher resistance in a LDR (light dependent resistor)?

A

When there’s a dimmer light

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30
Q

What does resistance depend on in a thermistor?

A

Temperature

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31
Q

When in there lower resistance in a thermistor?

A

Hotter temperatures

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32
Q

When in there higher resistance in a thermistor?

A

Cooler temperatures

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33
Q

What do resistance graphs look like for LDRs?

A

Resistance on y axis
Light intensity on x axis

The line goes downwards
The gradient is steep but gradually lowers

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34
Q

What do resistance graphs look like for thermistors?

A

Resistance on y axis
Temperature on x axis

The line goes downwards
The gradient is steep but gradually lowers

35
Q

How is each component connected in series circuits?

A

Connected in a line
End to end with a power sourxe

36
Q

What is current like at different points in a series circuit?

A

It’s the same everywhere
Current stays constant in a series circuit and doesn’t split between branches (as there aren’t any)

37
Q

What is potential difference like at different points in a series circuit?

A

The total source of potential difference (the voltage supplied by the power source) is shared between components

38
Q

What is resistance like at different points in a series circuit?

A

Total resistance of the components = the sum of their resistances
E.g. Rtotal = R1 + R2

39
Q

What happens when a resistor is added in a series circuit?

A

The total resistance of the circuit is increased

40
Q

What happens if a component breaks in a series circuit?

A

No current will flow

41
Q

How is each component connected in a parallel circuit?

A

Separately connected on each different branch of the circuit

42
Q

What is current like at different points in a parallel circuit?

A

Total current flowing around in the circuit = sum of the current flowing through each branch of the circuit
E.g. Itotal = I1 + I2

The total current entering a junction (new branch) = total current leaving the junction (new branch)

43
Q

What is potential difference like at different points in a parallel circuit?

A

The potential difference across each branch in a circuit is the same as the potential difference/voltage supplied by the power source
E.g. V1 = V2 = Vtotal

44
Q

What is resistance like in a parallel circuit?

A

The total resistance of resistors in parallel circuits, are less than the resistance of the smallest resistor

45
Q

What happens if you add a resistor into a parallel circuit?

A

The total resistance of the circuit will decrease

46
Q

What happens if a component breaks in a parallel circuit?

A

The components on other branches will still work as long as current still flows through them

47
Q

What equipment measures potential difference/voltage? How is it put into a circuit?

A

A voltmeter - put in parallel to the lamp or component

48
Q

What equipment measures current? How is it put into a circuit?

A

An ammeter - put in series of the circuit (not in parallel to the component)

49
Q

What equipment measures resistance? How is it put into a circuit?

A

An resistor - put in series of the circuit (not in parallel to the component)

50
Q

What is the correlation between work being done and charge?

A

When charge flows, work is done (so energy is transferred)

51
Q

What happens when energy is transferred electrically?

A

It’s then stored in an energy store

E.g. light switch energy stored in thermal energy store of heating element of a kettle

52
Q

What happens to some energy in circuits?

A

Some energy is dissipated to thermal energy stores when a current does work against resistance
Has a heating effect

53
Q

How does a current working against resistance create heat?

A
  1. Current flows through a resistor
  2. Electrons collide with, and energy transfer to, the lattice of ions in the resistor
  3. Ions vibrate more, so energy in thermal energy store increase s
  4. The resistor heats up
54
Q

Advantages of the heating effect caused by current working against resistors?

A

Used in electric heaters

55
Q

Disadvantages of the heating effect caused by current working against resistors?

A

Causes energy losses in circuits

56
Q

What is power?

A

Energy transferred per second

57
Q

What is a power rating?

A

The maximum amount of energy transferred between stores per second when the appliance is in use

58
Q

What is the correlation between current, potential difference and power?

A

As current through or potential difference across a device increases, the power increases

59
Q

What are the two types of electricity supply?

A
  1. Alternating current (a.c.)
  2. Direct current (d.c.)
60
Q

What is alternating current?

A

Current where the movement of charge constantly changes direction

61
Q

What is alternating current produced by?

A

An alternating voltage, where positive and negative ends of the potential difference keep altering

62
Q

What is alternating current used in?

A

Used as the UK’s main power supply

63
Q

What is direct current?

A

Current where movement of charge is only in one direction

64
Q

What is direct current produced by?

A

A direct voltage, where the potential different is only positive or only negative NOT BOTH

65
Q

What is direct current supplied by?

A

Cells and batteries

66
Q

What are the three key facts about the UK Mains Supply?

A

Has an a.c. supply
Frequency of 50Hz
Voltage of around 230V

67
Q

What are the three core cables?

A
  1. Live wire
  2. Neutral wire
  3. Earth wire
68
Q

What is the function of the live wire?

A

Provides alternating potential difference from mains supply

69
Q

What is the function of the neutral wire?

A

Completes the circuit

70
Q

What is the function of the earth wire?

A

Safety - stops appliance casing becoming live

71
Q

When does current flow through the earth wire?

A

When there’s a fault

72
Q

What is the potential difference between live wire and neutral OR earth wires?

A

230 V

73
Q

What is the potential difference between neutral wire and earth wires?

A

0 V

74
Q

How do electric shocks happen?

A
  1. Human makes contact with the live wire
  2. Large potential difference produced across body
  3. Current flows through body
  4. Electric shock - injury or even death
75
Q

What can happen when the live wire makes a connection with Earth?

A

It could cause a fire
It’s very dangerous

76
Q

What can make a live wire safe?

A

If a case of appliance is put on it

77
Q

What happens to a fuse and circuit breaker if it’s connected to a live wire and the wire has a surge of current? What does the lead to?

A

Fuse can melt
OR
Circuit breaker trips

Leads to the circuit breaking appliance being isolated - preventing fires and shocks

78
Q

What fuses are there?

A

3A
5A
13A

79
Q

What fuse do you choose if you know the operating current of a device?

A

The next one up
E.g. if a phone charger has an operating current of 2.1A, it’ll need a fuse of 3A

80
Q

COMPONENTS & CIRCUITS CORE PRACTICAL: How can a single component can be investigated?

A
  1. Set up a parallel or series circuit
  2. Put the voltmeter in parallel to the component you’re investigating and an ammeter in series to the component
  3. Vary output of potential difference of the source
  4. Take several pairs of readings for the current and voltage of the component
  5. Repeat the steps but re arrange the circuit (e.g. by adding more branches or components) and see how that affects the results
81
Q

COMPONENTS & CIRCUITS CORE PRACTICAL: In conclusion, what happens in a series and parallel when the source had an increased potential difference?

A

Series circuit: total current through the circuit also increases
Parallel circuit: total current through the circuit also increase

82
Q

COMPONENTS & CIRCUITS CORE PRACTICAL: In conclusion, what happens to the potential difference across each component in a series and parallel circuit?

A

Series: the potential difference supplied is shared between components
Parallel: the potential difference across the component is the same as the supplied potential difference

83
Q

COMPONENTS & CIRCUITS CORE PRACTICAL: In conclusion, what happens to the total current through a circuit in a series and parallel circuit?

A

Series: it’s the same everywhere and decreased as more components are added
Parallel: its equal to the sum of the current in the branches and increases as components are added

GCSE Physics (7 decks)

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