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GCSE Physics > Topic 10 - Electricity & Circuits > Flashcards

Topic 10 - Electricity & Circuits Flashcards

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1
Q

What 3 subatomic components make up an atom?

A

Electrons
Protons
Neutrons

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2
Q

Describe the structure of an atom

A

Neutrons and protons in nucleus

Electrons surrounding nucleus in shells

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3
Q

What are the charges of the particles in an atom

A

Proton +1
Neutron 0
Electron -1

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4
Q

In a closed circuit, if there is a potential difference in the circuit there will also be a…

A

Current

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5
Q

How is current defined

A

As the rate of flow of charge (or electrons) round a circuit

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6
Q

What are the units of charge

A

Coulombs (C)

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7
Q

What are the 2 ways that a component can be connected in a circuit

A

Series (same loop)

Parallel (adjacent loop)

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8
Q

Voltage is also known as…

A

Potential difference

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9
Q

How does the potential difference across 2 components vary when connected in series and parallel?

A

In series circuit, total PD is shared between each component

In parallel circuit, PD across each component is the same

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10
Q

If 2 resistors are connected in parallel, what can be said about their combined total resistance

A

Total resistance is less than the smallest of the 2 individual resistances

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11
Q

If 2 resistors are connected in series, what can be said about their total resistance

A

Their total combined resistance is equal to the sum of the two indiviso resistances

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12
Q

Where must a voltmeter be placed in a circuit

A

In parallel with the component that is being measures

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13
Q

Give an equation relating potential difference with energy transferred and charge

A

Potential difference (V) = energy transferred (J) / charge (C)

V = E/Q

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14
Q

A volt can also be described as…

A

Joule per coulomb

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15
Q

What is an electric current

A

The rate of flow of charge

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16
Q

State the equation linking charge, current and time. Give the units for the quantities involved

A

Q = I t

Charge(coulombs), Current(amperes), Time(secs)

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17
Q

What can be said about the value of current at any point in a single closed loop?

A

Current is the same at all points in a closed loop

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18
Q

What 2 factors does the current in a circuit depend on?

A 
Potential difference (V)
Resistance (R)
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19
Q

What equation supuld be used to calculate potential difference if current and resistance are known?

A 
V = I R
Potential difference (V) = Current (A) x Resistance (Ohms)
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20
Q

Whats an ammeter and where must it be connected in a circuit?

A

Measures current.

Placed in series with component its required to measure.

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21
Q

What happens when current reaches a junction in a circuit?

A

Current is conserved.

The total current remains the same and is split between the two branches.

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22
Q

How does resistance affect current in a circuit?

A

As the total resistance of a circuit increases, the current flowing through the circuit decreases

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23
Q

How can the current in a circuit be varied

A

Using a variable resistor

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24
Q

Give the equation linking current with resistance

A

P.D. (V) = current (A) x resistance (Ohms)

V = I R

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25
Q

How is total resistanve affected by 2 resistors in series

A

Total resistance increases

Is equal to the sum of 2 resistors

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26
Q

How is total resistance affected by 2 resistors in parallel

A

Total resistance decreases

Is less than the resistance of the resistor with lowest resistance

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27
Q

Whats an Ohmic Conductor. State conditiom required.

A

Conductor for which current and pd are directly proportional
Resistance remians constant as current changes
Temp must be constant

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28
Q

List 4 components for which resistance isnt constant as current changes

A

Filament lamps
Diodes
Thermistors
Light dependant resistors (LDRs)

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29
Q

What happens to resistance of a filament lamp as the temperature increases? Why?

A

Resistance increases
Metal ions have more kinetic energy so vibrate more, colliding more frequently with electrons as they flow through metal
This creates more resistance to current flow

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30
Q

Whats different about current flow through a diode?

A

Current only flows in one direction

Resistance is very high in other direction, preventing current flow

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31
Q

State what happens to the resistance of a thermistor as temperature increases

A

The thermistors resistance decreases

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32
Q

Give 2 examples of when a thermistor may be used

A

In a thermostat to turn a heater on below a certain temp

In a freezer to turn on a cooler when the temp becomes too high

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33
Q

State what happens to the resistance of an LDR as light intensity decreases

A

The LDRs resistance increases

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34
Q

Give an application for a LDR

A

Street lamps or night lights

When light levels drop (night) resistance increases and the light gains sufficient current to turn on

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35
Q

How do diodes work?

A

A diode only allows current to flow in one direction. If current is flowing right way, resistance is large for small voltages (uo until 0.6V) but then higher voltages become very small.

36
Q

What electrical component does this graph represent? —|-/

A

Diode

37
Q

What factors affect the energy transferred when charge flows through a component?

A

Amount of charge

Pd across the component

38
Q

Give an equation linking energy, current and pd

A

Energy (J) = pd (V) x current (A) x time (s)

E = V I t

39
Q

Define potential difference in terms of charge

A

The work done per unit charge

40
Q

Give an equation relating potential difference to charge

A 
Energy transferred (J) = charge (C) x pd (V) 
E = Q V
41
Q

When an electrical current flows through a resistor why does it heat up?

A

There are collisions between the electrons and ions in the resistors lattice. This causes a transfer of kinetic energy into thermal energy, which is released into the surroundings.

42
Q

How do low resistance wires reduce unwanted energy transfers

A

A smaller resistance will mean there are fewer collisions, therefore less energy will be wasted through heating

43
Q

What are some advantages of the heating effect

A

Its useful for appliances such as toasters or electrical fires, where the heat is the desired product

44
Q

What are some disavantages of the heating effect

A

Loss of energy as heat energy can make an appliance inefficient
If an appliance overheats it can catch fire or overheat which could ruin the device or injure user

45
Q

The energy transferred per second is also known as

A

Power

46
Q

Define power

A

The rate of energy transfer, or rate at which work is done

47
Q

What are the units of power

A

Watts W

48
Q

Give equation linking power and pd

A

Power (W) = current (A) x pd (V)

P = I V

49
Q

Give equation to work out power without pd

A

Power (W) = current squared (A) x resistance (Ohms)

P = I2 R

50
Q

Give an equation linking power and energy

A

Power (W) = energy (J) / time (s)

P = E/t

51
Q

Give both equations linking power with resistance

A

Power (W) = current squared (A) x resistance (Ohms)
P = I2 x R
Power (W) = pd squared (V) / resistance (Ohms)
P = V2 / R

52
Q

What word describes materials that electricity will pass through?

A

Conductors

53
Q

What word describes materials that electricity cannot pass through?

A

Insulators

54
Q

What components do you need to make a circuit that would make a small torch bulb light up?

A

Battery, connecting wires, lamp, switch is optional

55
Q

What are the two terminals of an electric cell labelled as?

A

Plus and minus

56
Q

In an electric circuit with a battery, which of these materials will conduct: copper, wood, salty water

A

Copper and salty water

57
Q

Which of these materials are insulators? Plastic metal air

A

Plastic and air

58
Q

What name is given to the negatively charged subatomic particles that cause an electric current?

A

Electrons

59
Q

Is mains voltage about 15 times, 150 times or 1500 times bigger than the voltage from a battery?

A

About 150 times

60
Q

If you connect some cells together in series, what forms

A

A battery

61
Q

Which line on the cell is the negative terminal

A

Shorter line

62
Q

Whats the difference between convectional current and flow of electrons?

A

Electrons flow from negative terminal of cell to positive terminal, convectional flows the other way

63
Q

What 2 conditions are needed to give a current in a circuit?

A

Closed circuit and potential difference

64
Q

What is current measured in

A

Amps/amperes

65
Q

What does AC mean?

A

Alternating current

66
Q

What is alternating current?

A

Current which is constantly changing between a negative and positive maximum

67
Q

What does DC mean?

A

Direct current

68
Q

What is direct current?

A

Current which takes a constant value

69
Q

Is mains electricity an AC or DC supply?

A

AC supply

70
Q

What is meant by the frequency of a supply?

A

The rate at which an AC current changes

71
Q

Whats the frequency and voltage of the UK mains electricity supply?

A

Frequency: 50Hz
Voltage: 230V

72
Q

What type of current do batteries and cells supply?

A

Direct current

73
Q

What is the power rating of an appliance?

A

Shows how much energy a device converts per second

74
Q

What wires does a typical domestic appliance have?

A

Live wire
Neutral wire
Earth wire

75
Q

What colour is the live wire?

A

Brown

76
Q

What colour is the neutral wire?

A

Blue

77
Q

What colour is the earth wire?

A

Green and yellow stripes

78
Q

Explain when the Earth wire does and doesnt carry a current

A

Under normal circumstances, no current flows through wire

Current flows when a fault occurs in the appliance

79
Q

What potential is the neutral wire at?

A

0 volts

80
Q

State the potential dofference between the live and earth wires

A

230 volts

81
Q

What is the purpose of the neutral wire?

A

To complete the circuit by connecting the appliance back to the mains supply

82
Q

For metal appliances, where is the earth wire connected to? Why?

A

Metal casing of appliance

If live wire touches the casing, current will flow through earth wire preventing electrocution

83
Q

How does a fuse stop a device getting damaged?

A

When current gets too high
fuse wire melts and breaks
stopping current flowing to appliance
preventing damage

84
Q

Why is it important to connect a fuse or switch to live wire

A

When switch turned off/fuse breaks it will break the circuit and stop current flowing through wire.
This provides a method to stop current flowimg into the appliance.

85
Q

Why is it dangerous to have a connection between the earth wire and live wire?

A

Can result in current surge, causing electrical shocks

86
Q

What is a current surge?

A

When significantly more current comes through the wire

GCSE Physics (6 decks)

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