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SA N4 Physics > Electricity and Energy > Flashcards

Electricity and Energy Flashcards

1
Q

What is current?

A

The charge transferred per second

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2
Q

What is meant by the potential difference (voltage) of a supply?

A

It is the number of Joules of energy given to each coulomb of charge passing through the cell

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3
Q

Which device measures current?

A

Ammeter

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4
Q

Which device measures voltage?

A

Voltmeter

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5
Q

Which device measures resistance?

A

Ohmmeter

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6
Q

What is the symbol for an ammeter?

A

Circle with an A in it.

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7
Q

What is the symbol for a voltmeter?

A

Circle with a V in it

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8
Q

What is the symbol for an Ohmmeter?

A

Circle with an Omega in it

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9
Q

How should an ammeter be connected to measure the current in a component?

A

It should be connected in series with the component

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10
Q

How should a voltmeter be connected to measure the voltage across a component?

A

It should be connected across the component

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11
Q

How can you identify a series circuit?

A

It is a circuit with only one path round it.

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12
Q

What is the rule for current in a series circuit?

A

The current is the same everywhere

I1=I2=I3

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13
Q

What is the rule for voltages in a series circuit?

A

The voltage across each component added together is equal to the supply voltage.

Vs=V1+V2+ …

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14
Q

What happens if you unscrew one of the lamps in the circuit below? Why?

A

The other lamps go out. There is a break in the circuit and the current does not have a complete route to the battery.

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15
Q

If you heat a conductor, what happens to it’s resistance?

A

It increases

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16
Q

How can a parallel circuit be identified?

A

It is a circuit with more than one path round it.

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17
Q

What is the rule for current in a parallel circuit?

A

The supply current is equal to the current in each branch added together.

IS = I1+I2+…

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18
Q

What is the rule for voltages in a parallel circuit?

A

The voltage across each branch is equal to the supply voltage.

VS=V1=V2= ….

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19
Q

Which circuit component is represented by the following diagram?

A

Cell

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20
Q

Which circuit component is represented by the following diagram?

A

Battery

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21
Q

Which circuit component is represented by the following diagram?

A

Switch

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22
Q

Which circuit component is represented by the following diagram?

A

Lamp

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23
Q

Which circuit component is represented by the following diagram?

A

Motor

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24
Q

Which circuit component is represented by the following diagram?

A

Loudspeaker

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25
Q

Which circuit component is represented by the following diagram?

A

Resistor

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26
Q

Which circuit component is represented by the following diagram?

A

Variable Resistor

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27
Q

Which circuit component is represented by the following diagram?

A

Thermistor

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28
Q

Which circuit component is represented by the following diagram?

A

Light Dependent Resistor

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29
Q

Which circuit component is represented by the following diagram?

A

Fuse

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30
Q

Which circuit component is represented by the following diagram?

A

Diode

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31
Q

Which circuit component is represented by the following diagram?

A

Light Emitting Diode

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32
Q

Which circuit component is represented by the following diagram?

A

Photovoltaic cell / solar cell

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33
Q

Which circuit component is represented by the following diagram?

A

Microphone

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34
Q

What is the energy chage in a battery?

A

Chemical to electrical

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35
Q

What is the energy change in a lamp?

A

Electrical to light (+ heat)

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36
Q

What is the energy change in a motor?

A

Electrical to kinetic

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37
Q

What is the energy change in a loudspeaker?

A

Electrical to sound

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38
Q

What is the energy change in a buzzer?

A

Electrical to sound

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39
Q

What is the energy change in an LED?

A

Electrical to light

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40
Q

What is the energy change in a photovoltaic cell?

A

Light to electrical

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41
Q

What is the energy change in a microphone?

A

Sound to electrical

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42
Q

What happens if you increase the resistance in a circuit?

A

The current will decrease

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43
Q

State two place a variable resistor can be used.

A

Light dimmer switch sped control on Scalextric cars volume control on a radio

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44
Q

State a device that can be used in a temperature sensor

A

Thermistor

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45
Q

State a device that can be used in a light sensor

A

LDR

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46
Q

What is a thermistor?

A

A resistor whose resistance changes with changes in temperature

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47
Q

What is a Light Dependent Resistor?

A

A resistor whose resistance changes with changes in light level

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48
Q

What is a fuse?

A

Safety device that protects the flex

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49
Q

Explain how a fuse works.

A

A fuse is a thin wire. If too much current passes through it, it will get hot and melt. This breaks the circuit.

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50
Q

How should a diode or LED be connected with a battery to light correctly?

A

Small line on battery points to small line on LED or diode.

51
Q

Why is an LED normally connected in series with a resistor?

A

Resistor is to protect the LED by limiting the current in the LED.

52
Q

What is the rule for selecting a fuse from a power rating?

A

Appliances less than 720W use a 3A fuse Appliances more than 720W use a 13A fuse

53
Q

What is power?

A

The energy transferred per second

54
Q

What two factors effect the running cost of an appliance?

A

The time it is used for The power rating of the appliance

55
Q

How can power losses be reduced in transmission lines?

A

By increasing the transmission voltage and so decreasing teh transmission current. Power loss P = I2R, so if the current is reduced the power lost is reduced.

56
Q

Suggest a way that we say ‘energy is lost’ (not converted to the type of energy we want)?

A
  • Heat lost to the surroundings due to friction
  • Sound energy lost to air because of vibrations
  • Energy lost as heat to the surroundings
  • Heat lost in heating up a container instead of the substance in it
57
Q

What causes pressure of a gas in a container?

A

Gas particles hitting the sides of a container

58
Q

Using Kinetic Theory state what happens to the pressure if you increase the temperature of a fixed mass gas in a fixed volume container.

A

Pressure increases

59
Q

Using Kinetic Theory state what happens to the pressure if you decrease the volume of a fixed mass gas at a constant temperature.

A

Pressure increases

60
Q

Using Kinetic Theory state what happens to the volume if you increase the temperature of a fixed mass gas at a fixed pressure.

A

volume will increase.

61
Q

What happens if you unscrew one of the lamps in a parallel circuit?

A

Other lamps stay on as they still have a complete route to the battery.

62
Q

What is the stated value of the mains?

A

230V, 50Hz

63
Q

When would you use a relay?

A

To switch on a high current ciruit using a low current circuit for safety.

64
Q

How does a relay work?

A
  • Close a switch to make a current flow in a wire.
  • This creates an electromagnet.
  • Electromagnet attracts metal switch.
  • This completes the second circuit and the lamp switches on.
65
Q

Which component does the symbol represent?

A

Buzzer

66
Q

What is the energy change in a buzzer?

A

Electrical to sound

67
Q

Using Kinetic Theory state what happens to the pressure if you decrease the temperature of a fixed mass gas in a fixed volume container.

A

Pressure decreases

68
Q

Using Kinetic Theory state what happens to the pressure if you increase the volume of a fixed mass gas at a constant temperature.

A

Pressure decreases

69
Q

Using Kinetic Theory state what happens to the volume if you decrease the temperature of a fixed mass gas at a fixed pressure.

A

Volume decreases

70
Q

What is meant by an analogue device?

A

A device that can take any value over a range

71
Q

What is meant by a digital device?

A

A device that is either ON or OFF or can only take set values.

72
Q

Name a digital input device.

A

Switch

73
Q

Name an analogue input device.

A

LDR, Thermistor, microphone, solar cell

74
Q

Name a digital output device

A

LED

75
Q

Name an analogue output device

A

Loudspeaker, motor, lamp

76
Q

Name an everyday device that gives an analogue reading.

A

A clock with hands, speedometer in car, analogue meter (has an arm that moves to give the reading)

77
Q

Name an everyday device that gives a digital reading.

A

Digital clocks, digital stopwatch, multimeter readings

78
Q

Suggest an output device that could give light out as a warning.

A

Lamp or LED

79
Q

Suggest an output device that could make a sound as a warning.

A

Buzzer or Loudspeaker

80
Q

Suggest an output device that could cause a fan to operate or to generate movement.

A

Motor

81
Q

Suggest an imput device that could detect changes in temperature

A

Thermistor

82
Q

Suggest an input device that could detect changes in light level

A

LDR (Light Dependent Resistor)

83
Q

How would you work out total resistance in a series circuit?

A

Add the resistances together

RT=R1+R2+R3

84
Q

Which logic gate is this?

A

AND

85
Q

Which logic gate is this?

A

OR

86
Q

Which logic gate is this?

A

NOT

87
Q

When will an AND gate give a ‘1’ or ON out?

A

When Input 1 AND Input 2 are ON or at ‘1’

88
Q

When will an OR gate give a ‘1’ or ON out?

A

When Input 1 is ON ‘1’ OR Input 2 is ON ‘1’ OR when Input 1 and Input 2 are ON ‘1’

89
Q

How does a NOT gate work?

A

Put in an ON ‘1’, get out an OFF ‘0’

Put in an OFF ‘0’, get out an ON ‘1’

90
Q

State Ohm’s Law

A

V = IR

Voltage = Current x Resistance

91
Q

Suggest one place that kinetic theory/model is used.

A
  • Weather balloons
  • Car tyres
  • Aerosol cans
  • Aircraft cabins
  • Gas tanks for diving
  • Pressurised containers - fire extinguishers
92
Q

State two methods of generating electrical energy

A
  • Solar cells
  • Wind turbines
  • Nuclear power station
  • Hydro electric
93
Q

State an advantage of generating electrical energy by using wind turbines.

A
  • Does not produce greenhouse gases
  • Renewable so it will not run out
94
Q

State a disadvantage of generating electrical energy by using wind turbines.

A
  • It may not always be windy enough to generate enough electrical energy
  • People object to them as they spoil the landscape
95
Q

State an advantage of generating electrical energy by using solar cells.

A
  • Does not produce greenhouse gases
  • Renewable so it will not run out
96
Q

State a disadvantage of generating electrical energy by using solar cells.

A
  • Many not have enough daylight to generate enough electrical energy
  • Can be expensive to install
97
Q

State an advantage of generating electrical energy by using nuclear power.

A
  • Does not produce any greenhouse gases
  • Produces a large amount of energy per kg of fuel
  • Fuel cells can be reprocessed an used again
98
Q

State a disdvantage of generating electrical energy by using nuclear power.

A
  • Produces radioactive waste
  • The waste must be stored for hundreds of years
  • Expensive to build and decomission
  • If there is an accident radioactive material can be released into the environment
99
Q

State an advantage of generating electrical energy by using hydro-electric.

A
  • Does not produce any greenhouse gases
  • The water is not used up in the process
100
Q

State a disadvantage of generating electrical energy by using hydro-electric.

A
  • A dam must be built and land is flooded to create the water storage, this can damage the environment
  • Loss of control of water flow down stream
101
Q

Which type of appliances consume the most energy?

A

Ones that are used for heating - kettle, electric shower etc.

102
Q

What is the efiiciency of a device a measure of?

A

How good an appliance is at converting the input energy to the wanted output energy.

A lamp converts electrical energy to light and heat, it would be more efficient if it did not produce heat.

103
Q

How do you calculate efficiency?

A

Efficiency = (Useful energy out / Energy In ) x 100

OR

Efficiency = (Useful Power Out / Power In) x 100

104
Q

If a power station is efficient, what is this on the environment?

A
  • Conserves resources (less input energy required to give the same output)
  • This can also reduce the impact on the environment
105
Q

What do the magetic field lines round a bar magnet look like?

A
106
Q

What do the field lines look like round two bar magnets?

A
107
Q

What do the field lines look like round two bar magnets?

A
108
Q

State two practical users of electromagnets.

A
  • Relays
  • Electric Bells
  • Loudspeakers
  • Fire door retainers
  • Maglev Trains
109
Q

Why do we sometimes use an electromagnet instead of a permanent magnet?

A

An electromagnet can be switched on and off.

110
Q

How can an electromagnet be constructed?

A

Wire wrapped wrapped round an iron nail. The ends of the wire connected to a battery.

111
Q

How can the strength of an electromagnet be varied?

A
  • More turns of wire = stronger electromagnet
  • Less turns of wire = weaker electromagnet
  • Increase the current through the wire / voltage across the wire = stronger magnet
  • Decrease the current through the wire / voltage acrossthe wire = weaker magnet
112
Q

What is the purpose of a transformer?

A

To increase or decrease a voltage

113
Q

What does a step up transformer do?

A

Increases the voltage

114
Q

What does a step down transormer do?

A

Decreases the voltage

115
Q

Why are transformers used in electrical transmission lines?

A

To step up the voltage. This decreases the current and reduces the power lost in the transmission lines. At the other end a step down transformer reduces the voltage ready for use in the home.

116
Q

What are the main parts of a transformer?

A

Primary Coli, Secondary Coil, Iron core

117
Q

Give one advantage of using overhead cables.

A
  • Easy to access for repairs.
  • Easy to spot where a repair is required
118
Q

Give a disadvantage of overhead cables.

A
  • They can look ugly in the countryside
  • High winds, heavy snow can bring them down
119
Q

Give an advantage of underground cables.

A
  • They cannot be seen so do not effect the landscape
  • Will not be effected by snow or heavy winds
120
Q

Give a disadvantage of underground cables

A
  • Have to dig them up for a repair
  • More difficult to find breaks
121
Q

In a traditional power station (coal, gas or oil fired) what are the main parts that help produce electrical energy?

A
  • Boiler
  • Turbine
  • Generator
122
Q

What is the energy change in a boiler?

A

Chemical to heat

123
Q

What is the energy change in a turbine? (Traditional power station)

A

Heat to Kinetic

124
Q

What is the energy change in a generator?

A

Kinetic to electrical

SA N4 Physics (4 decks)

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