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Physics > P1- Energy for the Home > Flashcards

P1- Energy for the Home Flashcards

(88 cards)

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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
How can you calculate wave speed?
**wave speed = frequency x wavelength**
26
Name the parts of the Electromagnetic Spectrum
1. radio 2. microwave 3. infrared 4. visible 5. ultraviolet 6. X-ray 7. gamma ray
27
How does **refraction **work?
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
28
What is **diffraction**?
The spreading out of a wave as it passes through a gap
29
How does diffraction change?
Most diffraction occurs when the gap is a similar size to the wavelength. Larger gaps show less diffraction
30
What is the **Morse code**?
A series of dots and dashes to represent letters of the alphabet
31
What type of signal is the Morse code?
Digital
32
What is the Morse code used for?
Signalling lamps as a series of short and long flashes of light
33
What is white light made of?
Different colours of different frequencies out of phase
34
What is laser light made of?
Single frequency, in phase and shows low divergence
35
How is laser light used for a Compact Disk (CD)?
* 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
36
What is **refraction**?
When light passes from two materials of different densities and changes direction
37
What happens to the angles when light passes from a more dense material to a less dense material?
The angle of **refraction** is larger than the angle of **incidence**
38
What is the critical angle?
When the angle of refraction is **90°**
39
What is **total internal reflection**?
When the angle of incidence is bigger than the critical angle, the light is reflected
40
How is TIR used for **optical fibres**?
Telephone conversations and computer data are transmitted long distances at the speed of light
41
How does an **endoscope **work?
* 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
How well doe **infrared **penetrate food?
Not very easily
43
How far does **microwave **radiation penetrate food?
1 cm into food
44
What materials can penetrate or reflect microwaves?
* penetrate glass or plastic * reflect shiny metal surfaces
45
Why does a microwave have a glass door?
* reflects the microwaves * so it does not burn body tissue
46
What does the amount of energy depend on?
Frequency or wavelength of wave
47
What frequency/ wavelength transfer more energy?
* High frequency * Short wavelength
48
How do ovens cook food by infrared radiation and microwave ovens by microwave radiation?
* 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
What wavelength range do microwaes have?
Between 1 mm to 30 cm
50
What wavelength is used by mobile phones and how much energy is transferred?
* longer wavelengths than microwave ovens * less energy is transferred by mobile phones
51
What is microwave radiation used for?
Communicating over long distances
52
What must **transmitters **and **receivers **be with each other?
In line of sight
53
Where must aerials be situated?
On top of high buildings
54
What are satellites used for?
Microwave communication
55
How do satellites work?
* signal from Earth is received, amplified and re-transmitted back to Earth * in line of sight because there are no obstructions in space
56
What are the concerns of use of mobile phone and positioning of phone masts?
* exposure to radio waves * can cause cancer if too much exposure
57
How can signals be affected?
* 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
What do infrared signals carry?
Information that allows electronic and electrical devices to be controlled
59
What does a **digital signal** look like?
60
What does an analogue signal look like?
61
What does the switchover from analogue to digital do for TV and radio?
* 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
What do **optical fibres** allow?
Data to be transmitted very quickly using pulses of light
63
Before an analogue signal is transmitted, where is it added to?
A **carrier wave**
64
What is the frequency of the carrier wave?
Higher than the signal being transmitted
65
What is **multiplexing**?
Combination of **multiple** signals into one signal trasmitted over a shared medium
66
What is wireless technology used by?
* radio and television * laptops * mobile phones
67
What happens to **radio waves** in the Earth's atmosphere?
It is **reflected** and **refracted**: * amount of refraction depends on the frequency of wave * there is less refraction at higher frequencies
68
Why can same frequencies be used by more than one radio station?
* radio stations are too far away from each other to interfere * in unusual weather, radio waves can travel further and the broadcasts interfere
69
How can interference be reduced?
By using **digital** signals
70
What does Digital Audio Broadcasting (DAB) provide?
* greater choice of radio stations * audio quality is not as good as FM signals * eliminates interference between other radio stations
71
How are radio waves affected by the **ionosphere**?
They are reflected: * behave like light in an optical fibre * undergo **total internal reflection**
72
What does and does not reflect radio waves?
Water reflects but land does not
73
How are microwaves affected by the ionosphere?
They pass though it
74
Where do communication satellites orbit?
Above the equato and take 24 hourse to orbit Earth
75
What are communication problems?
* 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
What does a **seismograph** show?
Different types of earthquake waves
77
What are **P waves?**
* **longitudinal pressure waves** * travel through Earth at 5km/s - 8km/s * can pass through solids and liquids
78
What are **S waves**?
* **transverse waves** * travel through Earth at 3km/s - 5.5km/s * can only pass through solids
79
How are P waves affected by the core?
* **refracted** by the core * paths taken by P waves allow scientists to work out the size of the core
80
How are S waves affected by the core?
* not travel through liquid * allows scientists to determine that the core is liquid
81
What does **ultraviolet** light cause?
A tan on skin
82
What cell produces a tan?
**Melanin** produces a pigment that causes a tan
83
Why do darker people not tan as easily?
The UV radiation is filtered out
84
How do you calculate the time to spend in Sun?
**maximum length of time to spend in the Sun = published normal burn time x SPF**
85
Where is ozone found?
In the **stratosphere**
86
What does ozone do?
Filter out UV radiation
87
What was the main cause of reducing the ozone layer?
Gases from aerosols and firdges
88
Where is the ozone thinnest?
Above the South Pole because ozone depleting chemicals work best in cold conditions

Physics (6 decks)

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