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Physics > P1- Energy for the Home > Flashcards

P1- Energy for the Home Flashcards

1
Q

What happens when the energy flows away from a warm object?

A

The temperature decreases

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2
Q

Which colours show what temperature in a thermogram?

A
  • white/ yellow - hot
  • black/ dark blue/ purple - cold
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3
Q

What happens to the **kinetic energy **when the temperature of a body increases?

A

The average kinetic energy of the particles increases

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4
Q

What is heat and temperature a measurement of?

And what scale is used?

A
  • heat is a measurement of internal energy and measured on the absolute scale
  • temperature is a measurement of hotness on an arbitrary scale
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5
Q

What is specific heat capacity?

A

Energy needed to raise the temperature of 1kg by 1°C, measured in **joules per kilogram degree Celsius **(J/kg °C)

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6
Q

How do you calculate energy transfer by specific heat capacity?

A

energy transferred =
mass x specific heat capacity x temperature change

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7
Q

What is specific latent heat?

A

The energy needed to melt or boil 1kg of the material, measured in **joule per kilogram **(J/kg)

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8
Q

How do you calculate energy transfer by specific latent heat?

A

energy transferred = mass x specific latent heat

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9
Q

How does double glazing reduce energy loss by conduction?

A

The gap between the two pieces of glass is filled with a gas or contains a vacuum

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10
Q

Why does the vacuum reduce energy transfer?

A

Because there are no particles, so it is impossible to transfer energy by conduction

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11
Q

How does loft insulation** **reduce energy loss by conduction?

A
  • warm air in home rises
  • energy is transferred through the ceiling by conduction
  • air in loft is warmed by the top of ceiling and trapped in loft insulation
  • no energy is transferred as both sides of the ceiling are the same temperature
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12
Q

How does loft insulation reduce energy loss by convection?

A
  • without loft insulation, the warm air in the loft can move by convection and heat the roof tiles
  • energy is transferred to the outside by conduction
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13
Q

How does cavity wall insulation reduce energy loss?

A
  • air in the foam is a good insulator
  • air cannot move by convection because it is trapped in the foam
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14
Q

How do insulation blocks reduce energy transfer by radiation?

A

Covered in shiny foil so:

  • energy from Sun is reflected back to keep homes cool in summer
  • energy from home is reflected back to keep homes warm in winter
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15
Q

How can energy be transferred by conduction?

A

Due to the transfer of kinetic energy between particles

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16
Q

How can energy be transferred by convection?

A

A gas expands when heated, making it less dense so it rises.

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17
Q

How can you measure density?

A

**density (kg/m3or g/cm3) **= mass/ volume

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18
Q

How can energy be transferred through a vacuum?

A

Radiation does not need material to transfer energy, so can be transferred.

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19
Q

How can you calculate energy efficiency?

A

**efficiency = useful energy output / total energy input **(x 100%)

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20
Q

How can energy transformations be shown?

A

Through Sankey diagrams

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21
Q

How can you calculate payback time?

A

payback time = cost of insulation / annual saving

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22
Q

What is the **amplitude **of a wave?

A

The maximum displacement of a particle from its rest position

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23
Q

What is the crest / peak and trough of a wave?

A
  • crest - highest point on a wave above its rest position
  • trough- lowest point on a wave below its rest position
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24
Q

What is the frequency of a wave?

A

The number of complete waves passing a point in one second

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25
Q

How can you calculate wave speed?

A

wave speed = frequency x wavelength

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26
Q

Name the parts of the Electromagnetic Spectrum

A
  1. radio
  2. microwave
  3. infrared
  4. visible
  5. ultraviolet
  6. X-ray
  7. gamma ray
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27
Q

How does **refraction **work?

A

The speed of the waves decrease as the wave enters a more dense medium and increases as the wave enters a less dense medium. The frequency stays the same but wavelength changes

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28
Q

What is diffraction?

A

The spreading out of a wave as it passes through a gap

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29
Q

How does diffraction change?

A

Most diffraction occurs when the gap is a similar size to the wavelength. Larger gaps show less diffraction

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30
Q

What is the Morse code?

A

A series of dots and dashes to represent letters of the alphabet

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31
Q

What type of signal is the Morse code?

A

Digital

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32
Q

What is the Morse code used for?

A

Signalling lamps as a series of short and long flashes of light

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33
Q

What is white light made of?

A

Different colours of different frequencies out of phase

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34
Q

What is laser light made of?

A

Single frequency, in phase and shows low divergence

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35
Q

How is laser light used for a Compact Disk (CD)?

A
  • surface of CD is pitted
  • pits represent the digital signal
  • laser light is shone onto the CD surface and difference in reflection provides the information for the digital signal
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36
Q

What is refraction?

A

When light passes from two materials of different densities and changes direction

37
Q

What happens to the angles when light passes from a more dense material to a less dense material?

A

The angle of refraction is larger than the angle of incidence

38
Q

What is the critical angle?

A

When the angle of refraction is 90°

39
Q

What is total internal reflection?

A

When the angle of incidence is bigger than the critical angle, the light is reflected

40
Q

How is TIR used for optical fibres?

A

Telephone conversations and computer data are transmitted long distances at the speed of light

41
Q

How does an **endoscope **work?

A
  • light passes along one set of optical fibres to illuminate the inside of the body
  • light is reflected
  • reflected light passes up another set of fibres to an eyepiece or camera
42
Q

How well doe **infrared **penetrate food?

A

Not very easily

43
Q

How far does **microwave **radiation penetrate food?

A

1 cm into food

44
Q

What materials can penetrate or reflect microwaves?

A
  • penetrate glass or plastic
  • reflect shiny metal surfaces
45
Q

Why does a microwave have a glass door?

A
  • reflects the microwaves
  • so it does not burn body tissue
46
Q

What does the amount of energy depend on?

A

Frequency or wavelength of wave

47
Q

What frequency/ wavelength transfer more energy?

A
  • High frequency
  • Short wavelength
48
Q

How do ovens cook food by infrared radiation and microwave ovens by microwave radiation?

A
  • energy absorbed by surface of food
  • kinetic energy of surface food particles increases
  • rest of food is heated by conduction
  • water or fat molecules in outer layers of food vibrate more
49
Q

What wavelength range do microwaes have?

A

Between 1 mm to 30 cm

50
Q

What wavelength is used by mobile phones and how much energy is transferred?

A
  • longer wavelengths than microwave ovens
  • less energy is transferred by mobile phones
51
Q

What is microwave radiation used for?

A

Communicating over long distances

52
Q

What must **transmitters **and **receivers **be with each other?

A

In line of sight

53
Q

Where must aerials be situated?

A

On top of high buildings

54
Q

What are satellites used for?

A

Microwave communication

55
Q

How do satellites work?

A
  • signal from Earth is received, amplified and re-transmitted back to Earth
  • in line of sight because there are no obstructions in space
56
Q

What are the concerns of use of mobile phone and positioning of phone masts?

A
  • exposure to radio waves
  • can cause cancer if too much exposure
57
Q

How can signals be affected?

A
  • adverse weather and large areas of water can scatter signals
  • curvature of the Earth limits line of sight, so transmitters have to be on tall buildings
  • microwaves do not show much diffraction
58
Q

What do infrared signals carry?

A

Information that allows electronic and electrical devices to be controlled

59
Q

What does a digital signal look like?

A
60
Q

What does an analogue signal look like?

A
61
Q

What does the switchover from analogue to digital do for TV and radio?

A
  • improve signal quality for both picture and sound
  • a greater choice of programmes
  • being able to interact with the programme
  • information services such as programme guides and subtitles
62
Q

What do optical fibres allow?

A

Data to be transmitted very quickly using pulses of light

63
Q

Before an analogue signal is transmitted, where is it added to?

A

A carrier wave

64
Q

What is the frequency of the carrier wave?

A

Higher than the signal being transmitted

65
Q

What is multiplexing?

A

Combination of multiple signals into one signal trasmitted over a shared medium

66
Q

What is wireless technology used by?

A
  • radio and television
  • laptops
  • mobile phones
67
Q

What happens to radio waves in the Earth’s atmosphere?

A

It is reflected and refracted:

  • amount of refraction depends on the frequency of wave
  • there is less refraction at higher frequencies
68
Q

Why can same frequencies be used by more than one radio station?

A
  • radio stations are too far away from each other to interfere
  • in unusual weather, radio waves can travel further and the broadcasts interfere
69
Q

How can interference be reduced?

A

By using digital signals

70
Q

What does Digital Audio Broadcasting (DAB) provide?

A
  • greater choice of radio stations
  • audio quality is not as good as FM signals
  • eliminates interference between other radio stations
71
Q

How are radio waves affected by the ionosphere?

A

They are reflected:

  • behave like light in an optical fibre
  • undergo total internal reflection
72
Q

What does and does not reflect radio waves?

A

Water reflects but land does not

73
Q

How are microwaves affected by the ionosphere?

A

They pass though it

74
Q

Where do communication satellites orbit?

A

Above the equato and take 24 hourse to orbit Earth

75
Q

What are communication problems?

A
  • radio waves are diffracted when they meet an obstruction
  • refraction in atmosphere needs to be taken into account
  • transmitting aerial needs to send a focused beam because its aerial is very small
  • trasmitted beam is slightly divergent
  • energy is lost from the edge of transmitting aerial because of diffraction
76
Q

What does a seismograph show?

A

Different types of earthquake waves

77
Q

What are P waves?

A
  • longitudinal pressure waves
  • travel through Earth at 5km/s - 8km/s
  • can pass through solids and liquids
78
Q

What are S waves?

A
  • transverse waves
  • travel through Earth at 3km/s - 5.5km/s
  • can only pass through solids
79
Q

How are P waves affected by the core?

A
  • refracted by the core
  • paths taken by P waves allow scientists to work out the size of the core
80
Q

How are S waves affected by the core?

A
  • not travel through liquid
  • allows scientists to determine that the core is liquid
81
Q

What does ultraviolet light cause?

A

A tan on skin

82
Q

What cell produces a tan?

A

Melanin produces a pigment that causes a tan

83
Q

Why do darker people not tan as easily?

A

The UV radiation is filtered out

84
Q

How do you calculate the time to spend in Sun?

A

maximum length of time to spend in the Sun = published normal burn time x SPF

85
Q

Where is ozone found?

A

In the stratosphere

86
Q

What does ozone do?

A

Filter out UV radiation

87
Q

What was the main cause of reducing the ozone layer?

A

Gases from aerosols and firdges

88
Q

Where is the ozone thinnest?

A

Above the South Pole because ozone depleting chemicals work best in cold conditions

Physics (6 decks)

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