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AQA P1 Revision2011 Specification

Infrared Radiation Kinetic Theory

Energy Transfer by

Heating

Heating and Insulating Buildings

Energy Transfers and

Efficiency

Transferring Electrical

Energy

Generating Electricity

The National Grid Waves

Reflection SoundRed Shift and the Big Bang

Theory

Infrared Radiation

a) All objects emit and absorb infrared radiation.b) The hotter an object is the more infrared radiation it radiates in a given time.c) Dark, matt surfaces are good absorbers and good emitters of infrared radiation. d) Light, shiny surfaces are poor absorbers and poor emitters of infrared radiation.e) Light, shiny surfaces are good reflectors of infrared radiation.

All objects emit (give out) some thermal radiation.

Matt black surfaces are the best emitters of radiation.

white silvermattblack

best emitter worst emitter

Certain surfaces are better at emitting thermal radiation than others.

Shiny surfaces are the worst emitters of radiation.

Which type of kettle would cool down faster: a black kettle or a shiny metallic kettle?

Emitting Infrared Radiation

Infrared waves heat objects that absorb (take in) them.

best emitter worst emitter

best absorber worst absorber

white silvermattblack

Matt black surfaces are the best absorbers of radiation.

Shiny surfaces are the worst emitters because they reflect most of the radiation away.

Why are solar panels that are used for heating water covered in a black outer layer?

Absorbing Infrared Radiation

Infrared Radiation – Exam Questions

Kinetic Theory

a) The use of kinetic theory to explain the different states of matter.b) The particles of solids, liquids and gases have different amounts of energy.

Kinetic TheoryAs you heat a substance, the heat energy is transferred to the particles

in the substance as kinetic energy. This causes the particles to move further apart, decreasing the density

of the substance.

Kinetic TheoryA loss of heat energy will cause the opposite effect.

Kinetic Theory – Exam Questions

Energy Transfer by Heating

a) The transfer of energy by conduction, convection, evaporation and condensation involves particles, and how this transfer takes place.b) The factors that affect the rate of evaporation and condensation.c) The rate at which an object transfers energy by heating depends on:• surface area and volume• the material from which the object is made• the nature of the surface with which the object is in contact.

d) The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating.

solid liquid gasParticles that are very close together can transfer heat energy as they vibrate. This type of heat transfer is called conduction.

Conduction is the method of heat transfer in solids but not liquids and gases.


Warmer regions of a fluid are less dense than cooler regions of the same fluid.

called a convection current.

The warmer regions will rise because they are less dense.The cooler regions will sink as they are more dense.This is how heat transfer takes place in fluids and is called convection.The steady flow between the warm and cool sections of a fluid, such as air or water, is


infraredwaves

The Earth is warmed by heat energy from the Sun.

There are no particles between the Sun and the Earth, so the heat cannot travel by conduction or by convection.

The heat travels to Earth by infrared waves. These are similar to light waves and are able to travel through empty space.

How does this heat energy travel from the Sun to the Earth?


Energy Transfer by HeatingHow is a vacuum flask able to keep hot

drinks hot and cold drinks cold?

2. The plastic (or cork) lid is an insulator and the screw top prevents convection currents escaping from the flask.

1. There is a vacuum between two layers of glass or steel, which prevents heat leaving or entering by conduction.

3. The walls have silvery surfaces, which prevent heat leaving orentering by radiation.

Energy Transfer by HeatingHeat loss through evaporation.

Energy Transfer by Heating – Quick Quiz

Energy Transfer by Heating – Exam Questions


a) U-values measure how effective a material is as an insulator.b) The lower the U-value, the better the material is as an insulator.c) Solar panels may contain water that is heated by radiation from the Sun. This water may then be used to heat buildings or provide domestic hot water.d) The specific heat capacity of a substance is the amount of energy required to change thetemperature of one kilogram of the substance by one degree Celsius.

Energy transferred = mass x specific heat capacity x temperature change

Heating and Insulating BuildingsA thermogram shows the distribution of heat over the surface of a house. It highlights where heat is being lost.

The white, yellow and red areas are the warmest, so these are the worst insulated parts of the house.

The blue and green areas are the coolest, so these are the best insulated parts of the house.

The specific heat capacity of a material is the amount of energy required to raise 1 kg of the material by 1 °C.

Energy is measured in joules (J).

It can be used to work out how much energy is needed to raise the temperature of a material by a certain amount:

energy specific heatcapacity

temperaturechange= mass x x

Mass is measured in kilograms (kg).

Temperature change is measured in °C.

Specific heat capacity is measured in J/kg°C.


Using the specific heat capacity of water (4200 J/kg°C), how much energy is needed to increase the

temperature of 600 g of water by 80°C in a kettle?

energy = 0.6 x 4200 x 80

= 201 600 J

Note: mass = 600 g = 0.6 kg

energy specific heatcapacity

temperaturechange= mass x x


Heating and Insulating Buildings – Exam Questions

Energy Transfers and Efficiencya) Energy can be transferred usefully, stored, or dissipated, but cannot be created or destroyed.b) When energy is transferred only part of it may be usefully transferred, the rest is ‘wasted’. c) Wasted energy is eventually transferred to the surroundings, which become warmer. The wasted energy becomes increasingly spread out and so becomes less useful.d) To calculate the efficiency of a device using:

EfficiencyTotal Energy Input

Useful Energy Output X 100=

The energy efficiency of a device can be calculated using this formula:

Energy efficiency does not have any units. It is a number between 0 and 1 which can be converted into a percentage by multiplying by 100.

Useful energy is measured in joules (J).

Total energy is measured in joules (J).

energy efficiency = useful output energy

total input energy

Energy Transfers and Efficiency

All the energy transfers (useful and wasted) that are associated with a device can be represented by a Sankey diagram.

A Sankey diagram uses arrows to represent all the output energies.

100 Jelectrical

energy(input)

20 Jelectrical

energy(input)

10 Jlightenergy(output)10 J

heat energy(wasted)

90 Jheat energy

(wasted)

10 Jlightenergy(output)

Energy efficient light bulb

Filament light bulb

The thickness of each arrow is proportional to the amount of energy involved at that stage.

Energy Transfers and Efficiency

Energy Transfers and Efficiency – Exam Questions

Transferring Electrical Energya) Examples of energy transfers that everyday electrical appliances are designed to bring about.b) The amount of energy an appliance transfers depends on how long the appliance is switched on and its power.c) To calculate the amount of energy transferred from the mains using:

Energy transferred = power x timed) To calculate the cost of mains electricity given the cost per kilowatt-hour.

Power is measured in kilowatts (kW) and the time is measured in hours (h), so what are the units of electricity measured in?

1 unit of electricity = 1 unit of electrical energy

Example:How many units of electricity is 17.6 kWh? 17.6 units

The amount of electrical energy (i.e. the amount of electricity) used by an appliance depends on its power and how long the electricity is used for.

electrical energy = power x time

= 1 kilowatt hour (kWh)

Transferring Electrical Energy

Electricity costs money, which is why every home has an electricity meter.

The units of electrical energy are called kilowatt hours (kWh).

The cost of an electricity bill is calculated from the number of units used.

The meter records how much electricity is used in a house in units of electrical energy.


The cost of electricity is the number of units of electrical energy multiplied by the cost per unit.

Example:How much would 10 units of electricity cost at a price of 9p per unit?

cost = 10 units x 9 p/unit

cost = number of units x cost per unit

= 90 p


A kettle uses 45.2 kWh of energy.If electricity costs 10 p per unit, how much does it cost to use the kettle?

Number of units:

Cost of electricity:

= 45.2 unitsnumber of units of electricity = number of kilowatt hours

= 452 p or £4.52= 45.2 units x 10 p / unit

cost = number of units x cost per unit


Transferring Electrical Energy – Exam Questions

Generating Electricitya) In some power stations an energy source is used to heat water. The steam produced drives a turbine that is coupled to an electrical generator.Energy sources include:

the fossil fuels (coal, oil and gas) which are burned to heat water or airuranium and plutonium, when energy from nuclear fission is used to heat waterbiofuels that can be burned to heat water.

b) Water and wind can be used to drive turbines directly.c) Electricity can be produced directly from the Sun’s radiation.d) In some volcanic areas hot water and steam rise to the surface. The steam can be tapped and used to drive turbines. This is known as geothermal energy.e) Small-scale production of electricity may be useful in some areas and for some uses, e.g. hydroelectricity in remote areas and solar cells for roadside signs.f) Using different energy resources has different effects on the environment. These effects include:

the release of substances into the atmosphere, the production of waste materials, noise and visual pollution, the destruction of wildlife habitats.

Energy resources can be classified into two groups.

Renewable energy resources can be replaced or regenerated and will never run out (at least not for a very long time).

Non-renewable energy resources will eventually run out – once used they cannot be used again.

Non-renewableRenewable

Examples: wind and solar. Examples: coal and oil.


Generating Electricity – Exam Questions

The National Grida) Electricity is distributed from power stations to consumers along the National Grid.b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables.c) The uses of step-up and step-down transformers in the National Grid.

The National Grid

The voltage is altered in The National Grid with the use of step-up and step-down transformers.

The voltage is ‘stepped up’ when it leaves the power station to reduce the current - this reduces the amount of energy loss

The voltage is then ‘stepped down’ before it reaches our homes

Power stationStep up

transformerStep down

transformerHomes

The National Grid – Exam Questions

Wavesa) Waves transfer energy.b) Waves may be either transverse or longitudinal.c) Electromagnetic waves are transverse, sound waves are longitudinal and mechanical waves may be either transverse or longitudinal.d) All types of electromagnetic waves travel at the same speed through a vacuum (space).e) Electromagnetic waves form a continuous spectrum.f) Longitudinal waves show areas of compression and rarefaction.g) Waves can be reflected, refracted and diffracted.h) Waves undergo a change of direction when they are refracted at an interface.i) The terms frequency, wavelength and amplitude.

j) All waves obey the wave equation: v = f x k) Radio waves, microwaves, infrared and visible light can be used for communication.

The vibrations are at 90O or right angles to the direction of the waves.

Wave Direction

Vibrations Vibrations

Transverse Waves

Certain parts of a transverse wave have special names.

peak

trough

The high points of a transverse wave are called peaks and the low points of a transverse wave are called troughs.

Transverse Waves

The wavelength of any wave is the distance between two matching points on neighbouring waves.

The wavelength is the same whichever two matching points are used to measure this distance.

wavelength

wavelength

wavelength

The symbol used to represent wavelength is .

Transverse Waves

The amplitude of any wave is the maximum distance a point moves from its rest position.

The amplitude of a transverse wave is the height of a peak or trough from the wave’s rest position of the wave.

amplitude

amplitude

The larger the amplitude, the greater the energy of the wave.

Transverse Waves

The frequency is the number of waves passing any point each second.

frequency = number of waves past a point / time

frequency is measured in hertz (Hz)

1 wave per second = 1 Hz

If this set of transverse waves pass a point in one second, what is the frequency? 4 Hz

Transverse Waves

Wave Direction

Vibrations

The vibrations are parallel to the direction of the waves.

Longitudinal Waves

Where the particles in a longitudinal wave bunch together are called compressions, where they spread out are called rarefactions.

Longitudinal Waves

The wavelength of a longitudinal wave is measured from one compression to another, or one rarefaction to another.

wavelength

wavelength

Longitudinal Waves

Wave speed is measured in metres per second (m/s).

For any set of waves, the wave speed (v) can be calculated from the frequency (f) and wavelength () using this formula:

What are the units of speed, frequency and wavelength?

Frequency is measured in hertz (Hz).

Wavelength is measured in metres (m).

wave speed = frequency x wavelengthv = f x

Waves

These waves are travelling across the surface of a pond. The length of each wave is 0.25 m.

From this example, the connection between speed, frequency and wavelength is:

speed = frequency x wavelength

0.5 m/s = 2 Hz x 0.25 m

This means that the waves travel 0.5 m each second, so the speed of the waves is 0.5 m/s.

Two waves pass the duck each second, so the frequency is 2 Hz.

Waves

Waves – Exam Questions

Reflectiona) The normal is a construction line perpendicular to the reflecting surface at the point of incidenceb) The angle of incidence is equal to the angle of reflection.c) The image produced in a plane mirror is virtual, upright and laterally inverted.

A plane mirror reflects light regularly so it produces a clear image, which is the same size as the object.The image appears the same distance behind the mirror as the object is in front of it.

When an object is reflected in a plane mirror, left appears as right and right appears as left. This type of reversal is called lateral inversion.

What is different about the image compared to the object?

Reflection

Reflection – Exam Questions

Sounda) Sound waves are longitudinal waves and cause vibrations in a medium, which are detected as sound.b) The pitch of a sound is determined by its frequency and loudness by its amplitude.c) Echoes are reflections of sounds.

Sound waves can be studied with this type of equipment.

signal generator

oscilloscopeloudspeaker

A signal generator produces different types of signals.

A loudspeaker converts signals from the signal generator into sound waves.

An oscilloscope shows wave patterns and allows us to ‘see’ sound.

Sound

The larger the amplitude of the wave on the trace, the louder/quieter the sound.

A sound can be quiet or loud.

loud soundquiet soundOn an oscilloscope trace, the loudness of a sound is shown by the height of the wave. This is called the amplitude.

Which word should be crossed out in this sentence?

Sound

Sound A is the loudest.

Which trace represents the loudest sound?

Sound A has the largest amplitude (i.e. the tallest waves), so it is the loudest of these two sounds.

A B

Sound

A sound can be high or low – this is the pitch of the sound.

low pitch sound high pitch soundOn an oscilloscope trace, the pitch of a sound is shown by how many waves there are. This is called the frequency.

Which word should be crossed out in this sentence?

The greater the number of waves across the oscilloscope trace, the lower/higher the frequency and pitch.

Sound

Which trace represents the sound with the highest pitch?

Sound B has the highest pitch.

Sound B has the most number of waves across the oscilloscope – it has the highest frequency and so has the highest pitch.

BA

Sound

The sound wave is reflected back from the surface.

This is called an echo.

What happens when a sound wave meets a hard flat surface?

Sound

Sound – Exam Questions

Red Shift and the Big Bang Theorya) If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency. This is known as the Doppler effect.b) There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies are, the faster they are moving, and the bigger the observed increase in wavelength. This effect is called red-shift.c) How the observed red-shift provides evidence that the universe is expanding and supports the ‘Big Bang’ theory (that the universe began from a very small initial point). d) Cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe. It comes from radiation that was present shortly after the beginning of the universe.e) The ‘Big Bang’ theory is currently the only theory that can explain the existence of CMBR.

The Doppler effect means that sound moving away from an observer appears to be lower in frequency.

It has also been observed that the further away a galaxy is, the greater the amount of red shift.

This means the distant galaxies must be moving away from the Earth.

The same thing happens with light from distant galaxies, which appears to be shifted towards the low frequency, red end of the spectrum.

This means that very distant galaxies must be moving fasterthan near, all of which is evidence for the Big Bang theory.

Red Shift and the Big Bang Theory

The observation of red shift is a key piece of evidence for the Big Bang theory about the origin of the Universe.

The other key piece of evidence for the Big Bang theory is cosmic microwave background radiation (CMBR).

This states that the Universe ‘began’ with a colossal explosion 13,700 million years ago and has been expanding ever since.

CMBR is radiation remaining from the Big Bang explosion and fills the whole of the Universe.


• The Big Bang is the most widely recognised scientific theory on how the Universe began.

• It states that the Universe began from a very small, very dense and very hot initial point.

• It burst outwards in a great explosion, and all matter and space was created in the Big Bang.

• It is even thought that this was the moment when time began.


• The first piece of evidence for the Big Bang is from data collected on red-shift.

• Red-shift shows us that galaxies which are furthest away from us are moving faster than galaxies closer to us.

• The galaxies are a bit like coloured sparks from an exploding firework. The sparks moving fastest travel the furthest.

• If you could run time backward you would see the sparks all starting in one point. The same is true for galaxies.


• In the 1960s two scientists called Wilson and Penzias noticed that a form of microwave radiation was affecting their readings.

• The electromagnetic radiation was everywhere and is now called cosmic microwave background radiation (CMBR).

• CMBR is explained as being heat left over from the Big Bang.

• As the Universe exploded, it cooled and the radiation was stretched out. Today this radiation is in the microwave region of the electromagnetic spectrum


Red Shift and the BBT – Exam Questions

p1 revision poweroint

Technology

transfer of energy

heat energy travel

loss of heat energy

kinetic energy

type of heat transfer

method of heat transfer

heating heat loss

distribution of heat