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Physics > P1- Energy For The Home > Flashcards

P1- Energy For The Home Flashcards

0
Q

When does the temperature of an object decrease?

A

When energy flows away from a warm object.

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1
Q

In what direction does energy flow? And in what form?

A

It flows from a warmer body to a colder body.

In the form of heat.

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2
Q

What is a thermogram?

A

It uses colour to show temperature.
Hottest parts are white/yellow.
Coldest parts are black/dark blue/purple.

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3
Q

What is temperature?

A

A measure of hotness on an arbitrary scale.

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4
Q

What does temperature allow?

A

One object to be compared to another.

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5
Q

To measure temperature, what do you not always necessarily need?

A

A thermometer.

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6
Q

What happens when the temperature of a body increases?

A

The average kinetic energy of the particles increases.

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7
Q

What is heat?

A

A measurement of internal energy.

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8
Q

What is heat measured on?

A

An absolute scale.

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9
Q

What is Specific Heat Capacity?

A

The energy needed to raise the temperature of 1kg by 1 degree Celsius.

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10
Q

What is Specific Heat Capacity measured in?

A

J/Kg*C

Joules per kilogram degree Celsius.

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11
Q

What happens when an object is heated and it’s temperature rises?

A

Energy is transferred.

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12
Q

M x C x /\ T

What is this equation for?

A

Energy transferred.

Mass x specific heat capacity x temperature change

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13
Q

What is Specific Latent Heat?

A

The energy needed to melt or boil 1kg of the material.

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14
Q

What is Specific Latent Heat measured in?

A

J/Kg

Joules per kilogram.

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15
Q

(SLH)

When an object is ______ and it ___________, __________ is________, but temperature remains ________.

A

When an object is heated and it changes state, energy is transferred, but the temperature remains constant.

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16
Q

What is this equation for?

Mass x SLH

A

Energy transferred.

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17
Q

When a substance changes state, why is there no change in temperature?

A

Because energy is needed to break the bonds that hold the molecules together.

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18
Q

How does double glazing reduce energy loss?

A

By conduction.

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19
Q

How does double glazing work?

A

The gap between the two pieces of glass are filled with a gas or contains a vacuum.
Particles in a gas are so far apart that it is difficult to transfer energy.
There are no particles in a vacuum so it is impossible to transfer energy by conduction.

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20
Q

How does loft insulation reduce energy loss?

A

By conduction and convection.

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21
Q

How does loft insulation work?

A

Warm air in the home rises.
Energy is transferred through the ceiling by conduction.
Air in the loft is warmed by the top of the ceiling and is trapped in the loft insulation.
Both sides of the ceiling are at the same temperature and so no energy is transferred.

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22
Q

What would happen if you didn’t have loft insulation?

A

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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23
Q

How does cavity wall insulation reduce energy loss?

A

By conduction and convection.

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24
Q

How does cavity wall insulation work?

A

The air in the foam is a good insulator and the air cannot move by convection because it is trapped in the foam.

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25
Q

What are insulation blocks and how can they reduce energy transfer?

A

They are used to build new homes and have shiny foil on both sides. This reduces energy transfer by radiation.

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26
Q

How do insulation blocks work?

A

Energy from the sun is reflected back to keep the home cool in summer. Energy from the home is reflected back to keep the home warm in winter.

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27
Q

What three ways can energy be transferred and how?

A

Conduction- due to the transfer of kinetic energy between particles.
Convection- a gas expands when it is heated. This makes it less dense so it rises.
Radiation- does not need a material to transfer energy.

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28
Q

What is the unit if density?

A

Kg/m^3 or g/cm^3

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29
Q

Energy can be transferred through a ______ by _______.

A

Vacuum by radiation.

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30
Q

What can be shown in Sankey Diagrams?

A

Energy transformations.

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31
Q

What is the equation for payback time?

A

Cost of insulation
_________________

Annual saving

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32
Q

What is payback time?

A

The amount of time it takes for you to start saving money from the insulation installed in your home.

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33
Q

Everything that transfers energy will w______ some to the s_______.

A

Waste, surroundings.

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34
Q

Buildings that are energy efficient are what?

A

Well insulated. Little energy is lost to the surroundings.

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35
Q

What is the amplitude of a wave?

A

(How high the wave is)

The MAXIMUM displacement of a particle from its rest position.

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36
Q

What is the crest of a wave?

A

The highest point on a wave above its rest position.

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37
Q

What is the trough of a wave?

A

The lowest point on a wave below its rest position.

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38
Q

What is the wavelength of a wave?

A

The distance between two successive points on a wave.

When they have the same displacement and moving in the same direction

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39
Q

What is the frequency of a wave?

A

The number of complete waves passing a point in one second.

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40
Q

What is this equation for?

Frequency x Wavelength

A

Wave speed.

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41
Q

In the electro magnetic spectrum, which has the biggest wavelength?

A

Radio waves.

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42
Q

In the electro magnetic spectrum, which has the highest frequency?

A

Gamma rays

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43
Q

List the electro magnetic spectrum from lowest frequency to highest.

A 
Radio                              Lowest
Microwave
Infrared
Visible 
Ultraviolet
X ray
Gamma ray                      Highest
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44
Q

List the electromagnetic spectrum from highest frequency to lowest.

A 
Gamma 
X ray
Ultra violet
Visible
Infrared
Microwave
Radio
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45
Q

Give an example of an optical instrument.

A

Periscope

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46
Q

What do optical instruments use?

A

Two or more plane mirrors.

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47
Q

When does retraction occur?

A

When the speed of waves decreases as the wave enters a more dense medium and increases as the wave enters a less dense medium.

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48
Q

In refraction what stays the same and what changes?

A

Frequency stays the same but wavelength changes.

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49
Q

What is diffraction?

A

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

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50
Q

What does the size of a communication receiver depend on?

A

The wavelength and the radiation.

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51
Q

When does the most diffraction occur?

A

When the gap is a similar size to the wavelength.

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52
Q

In diffraction, what do gaps larger than the wavelength do?

A

Show less diffraction.

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53
Q

Diffraction effects are noticeable in what two things?

A

Telescopes and microwaves.

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54
Q

What is morse code?

A

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

55
Q

What is morse code an example of?

A

A Digital signal.

56
Q

How is morse code used?

A

By signalling lamps as a series of short and and long flashes of light.

57
Q

When is a signal almost instantaneous?

A

When it is sent by light, electricity, microwave or radio.

58
Q

List 3 debatable points on the advantages and disadvantages of methods of transmission.

A

Can the signal be seen by others?
Can the wires be cut?
How far does the signal have to travel?

59
Q

White light is made up of what?

A

Different colours of different frequencies out of phase.

60
Q

What has only one single frequency?

A

Laser light.

61
Q

What is special about laser light?

A

Has a single frequency
In phase
Shows low divergence

62
Q

What is laser light used for?

A

To read the surface of a compact disc (CD)

63
Q

How can laser light read CD’s??

A

CDs.
The surface of the CD is pitted.
The pits represent the digital signal.
Laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal.

64
Q

What normally happens when light travels from one material to another?

A

Refracted.

65
Q

What is the angle of incidence?

A

The angle caused by a wave entering.

66
Q

What is the angle of refraction?

A

The angle when it is going away.

67
Q

When is the angle of refraction larger than the angle of incidence?

A

When it is passing from a more dense material into a less dense.

68
Q

What is the critical angle?

A

When the angle of refraction is 90 degrees, we call the angle of incidence, the critical angle.

69
Q

When is total internal reflection achieved?

A

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

70
Q

How are telephone conversations and computer data transmitted long distances?

A

They are transmitted along optical fibres at the speed of light.

71
Q

What is the speed of light in glass?

A

200,000km/s

72
Q

Why are some fibres coated?

A

To improve reflection.

73
Q

What do doctors use to see inside a body without surgery?

A

An endoscope.

74
Q

How do doctors see in a body without surgery?

Explain.

A

Endoscope
Light passes along one set of optical fibres to illuminate the inside of the body.
The light is reflected.
The reflected light passes up another set of fibres to an eyepiece or camera.

75
Q

Infrared radiation does not _____ ______ easily.

A

Penetrate food

76
Q

How far do microwaves penetrate food?

A

1cm

77
Q

What can microwaves also penetrate?

A

Glass or plastic

78
Q

What can microwaves not penetrate?

A

They are reflected by shiny metal surfaces.

79
Q

What is special about microwave ovens?

A

They have special glass in the door to reflect microwaves.

80
Q

What can microwaves do to body tissue?

A

Cause it to burn.

81
Q

In cooking and communicating, energy is transferred by what?

A

Waves.

82
Q

In the electromagnetic spectrum, what does the amount of energy depend on?

A

The frequency or wavelength of a wave.

High frequency transfers more energy.

83
Q

How do normal ovens cook food?

A

By infrared radiation.

84
Q

Explain how normal ovens cooks food.

A

Energy is absorbed by the surface of food.
The kinetic energy of the surface of the food particles increases.
The rest of the food is heated by conduction.

85
Q

Explain how do microwave ovens cook food

A

They cook food by radiation.
The microwaves penetrate 1cm into food.
The outer layers of water or fat molecules vibrate more and kinetic energy increases.
Energy is transferred to the rest of the food by conduction.

86
Q

Microwaves have wavelengths between 1___ and 30_____

A

1mm and 30 cm

87
Q

Mobile phones use longer wavelengths than m____ o____ so less energy is t_______ by mobile phones.

A

Longer, microwave ovens, less, transferred.

88
Q

What else can microwave radiation be used for?

A

Used to communicate over long distances.

89
Q

In microwave radiation, where are the transmitter and receiver?

A

They must be in line of sight. Aerials are normally situated on top of high buildings.

90
Q

Satellites are used for what?

A

Microwave communication.

91
Q

What are satellites used for and how?

A

Microwave communication.
The signal from earth is received, amplified and re-transmitted back to earth.
Satellites are in line of sight because there are no obstructions in space.
Large aerials can handle thousands of phone calls and television channels all at once.

92
Q

There are concerns about the use of mobile phones and where p___ m_____ are situated.

A

Mobile phones. Phone masts.

93
Q

Why do scientists publish results of their studies?

A

To allow others to check their findings.

94
Q

Signal strength for mobile phones can change a lot over a short distance. Why?

A

Signal strength, short distance.
Microwaves do not show much diffraction.
Adverse weather and large areas of water can scatter the signals.
The curvature of the Earth limits the line of sight so transmitters have to be on tall buildings or close together.

95
Q

Mobile phones are banned on planes and many hospitals, why?

A

They can interfere with sensitive equipment.

96
Q

Infrared signals carry information that allows what?

A

Electronic and electrical devices to be controlled.

97
Q

Pressing the button on a remote control device does what?

A

Completes the circuit.

98
Q

What happens when you press a button on a remote control?

A

The circuit is complete.
A coded signal is then sent to a light emitting diode or LED at the front of the remote. The signal includes a start command, the instruction command, a device code and a stop command.
The LED transmits a series of pulses. This is received by the device and decided to allow the television to change channel or volume.

99
Q

What is LED?

A

Light-emitting diode.

100
Q

Why might the switchover from analogue to digital be delayed?

A

Until more people buy digital radios.

101
Q

The ‘switchover’ for both radio and tv means what?

A

Improved 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.

102
Q

What do optical fibres allow?

A

Data to be transmitted very quickly using pulses of light.

103
Q

Explain analogue signals.

How they are sent and about interference.

A

Before an analogue signal is transmitted, It is added to a carrier wave. The frequency of the carrier wave is usually much higher. The combined wave is transmitted. Interference from another wave can also be added and transmitted. If the wave is amplified,the interference is amplified too.

104
Q

What happens before an anole the signal is transmitted?

A

It is added to a carrier wave.

105
Q

What is special about a carrier waves ___?

A

It’s frequency is usually much higher.

106
Q

What happens with interference on digital signals?

A

It is not apparent because the digital signal only has two values.

107
Q

What does multiplexing allow?

A

A large number of digital signals to be transmitted at the same time.

108
Q

If a, b and c goes into the multiplexer, what does it look like as it is transmitted and at the demultiplexer?

A

Transmitted as:
abcabcabcabcabcabcabcabc

Demultiplexer:
aaaaaaaa
bbbbbbbb
cccccccc

109
Q

What is wireless technology used by?

A

Radio and television
Laptops
Mobile phones

110
Q

Radioaves are r_______ and r________ in the earths surface.

A

Reflected and refracted.

111
Q

What does the amount of diffraction by radio waves depend on?

A

The frequency of the wave

There is less diffraction at higher frequencies.

112
Q

How do radio stations work?

A

They broadcast signals with a particular frequency.

113
Q

The same frequency can be used by the same radio station, how?

A

If Radiostations are too far away from each other to interfere
But in unusual weather conditions, radio waves can travel further and the broadcasts interfere.

114
Q

How can interference be reduced?

A

If digital signals are used.

115
Q

Advantages and disadvantages of DAB

A

DAB is digital audio broadcasting.
Provides better choice of radio stations
Eliminates interference between other radio stations
Audio quality is not as good as fm signals currently used.

116
Q

What are radio waves reflected from?

A

The ionosphere.

117
Q

How do radio waves behave like light in an optical fibre?

A

They undergo total internal reflection in the ionosphere.

118
Q

What reflects radio waves, water or land mass?

A

Water.

119
Q

What does continued reflection of radio waves by the ionosphere and oceans allow?

A

radiowaves to be received from am areial that is not in line of site.

120
Q

What do microwaves pass through that radiowaves are reflected by?

A

Ionosphere.

121
Q

How are microwave signals travelling?

A

Received by robing satellites, amplified and then retransmitted back to earth.

122
Q

What is a communication satellites orbit?

A

They take 24 hours to orbit the earth

Orbit above the equator.

123
Q

What are 5 communication problems?

A

Radiowaves are diffracted when they meet an obstruction
Refraction in the atmosphere needs to be taken into account when sending a signal to a satellite.
The transmitting aerial needs to send a focused beam to the satellite because it’s aerial is very small.
The transmitted beam is slightly divergent.
Some energy is lost from the edge of the transmitting aerial because of diffraction.

124
Q

What does a seismograph show?

A

Different types of earthquake wave.

125
Q

What do L waves do?

A

Travel round the earths surface very slowly.

126
Q

What are P waves and where do they travel?

A

Longitudinal pressure waves
Travel through the earth at between 5km/s to 8km/s
Can pass through solids and liquids
Refracted by the core
Paths taken By p waves mean that scientists can work out the size of earths core.

127
Q

What are S waves, where do they travel?

A

TranSSSverse waves
Travel through the earth at between 3km/s and 5.5km/s
Can only pass through solids
Are not detected on the opposite side of the earth to an earthquake
Will not travel through liquid, this tell scientists that the earths core is made of liquid.

128
Q

What is a tan caused by?

A

The action of ultraviolet light on the skin
Cells on the skin produce melanin, a pigment that produces a tan
People with darker skin do not tan as easily because ultraviolet radiation is filtered out

129
Q

How can you reduce the risk of sunburn?

A

Don’t stay in the sun as long

Use sunscreen with a high SPF (sun protection factor) to reduce risks.

130
Q

What are people becoming more aware of in sun burn/tan?

A

More aware of the dangers of exposure to ultraviolet radiation including the use of sunbeds.

131
Q

At first, what did scientists think about the ozone?

A

They didn’t believe that there was thinning of the ozone layer, they thought their instruments were faulty but other scientists confirmed the results and increased confidence in the findings.

132
Q

Where is ozone and what does it do?

A

Found in stratosphere

Helps to filter out ultraviolet radiation.

133
Q

What can reduce the thickness of the ozone layer?

A

CFC gases from aerosols and fridges destroy ozone. This increases the potential danger to humans.

134
Q

Where is the ozone layer at its thinnest?

A

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

135
Q

How can scientists monitor the thickness of the ozone layer?

A

Using satellites.

136
Q

How has the world tried to stop the depleting of the ozone layer?

A

There is an international agreement to reduce CFC emissions.

Physics (5 decks)

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