Physics - Module 1

Energy Transfer by Heating - 1.1 Infra-Red Radiation

Infra Red Radiation is part of the Electromagnetic Spectrum (Just to the right of the visible spectrum).

"IT DOES NOT REQUIRE PARTICLES"

Some Key Facts -

• ALL objects emit and absorb Infra Red Radiation
• The hotter the object the more Infra Red Radiation is emitted.
• The colder the object the less Infra Red Radiation is emitted.
• The Sun emits Infra Red Radiation.
• IF an objects surroundings are colder than it, it will emit Infra Red Radiation.
• IF an objects surroundings are warmer than it, it will absorb Infra Red Radiation.

    Infra Red Radiation can travel through a vacuum (e.g Space) because it does not require particles. This is how radiation from the Sun reaches Earth. We can feel Infra Red Radiation because it feels warm. It travels in electromagnetic waves.

Energy Transfer by Heating - 1.2 Surfaces and Radiation

• Black, matte surfaces are the best absorbers and emitters of radiation
• Black, matte surfaces are bad reflectors of radiation

• Light, shiny surfaces are the worst absorbers and emitters of radiations
• Light, shiny surfaces are great reflectors of radiation.

Energy Transfer by Heating - 1.3 States of Matter

Solids

• Fixed Shape. High Density
• Vibrations only
• Can't carry charge (except metals).

Liquids

• Move about randomly. Medium density and moderate speed
• No fixed shape
• Can't carry charge.

Gases

• Move fast, very low density and random movement. Most energy No fixed shape

Energy Transfer by Heating - 1.4 Conduction

Solids are good conductors. Gases and Liquids are poor conductors. 

Occurs by following :-

- An end of a solid is heated. The particles gain more energy and vibrate faster

- They collide with neighbouring particles who pass on the 'energy'.

 This occurs in metals because metals have a free electron (gains Kinetic energy) which can pass on the 'energy' faster. Wood and other solids take longer to conduct Heat energy because they have no free electrons to speed up the conduction process.

  Materials such as fibreglass and wool are good 'insulators' - a material that does not conduct heat well - because they contain trapped air. 

Energy Transfer by Heating - 1.5 Convection

Convection works best in Fluids (Liquids and Gases)

Convection - This is the circulation of a fluid caused by heating.

Convection Current

• A fluid is heated by a heat source.
• The particles in the fluid heat up and expand making them less dense.
• Due to the lower density they rise. New particles replace them.
• They will keep moving upwards until they are either too far away OR they have hit a barrier (i.e. a ceiling, if this is the case they'll just move along the ceiling)
• The further away from the heat source they are the cooler they become - loss of heat energy.
• They contract and become more dense.
• They sink down to the ground and pushed along it until they reach the heat source. The cycle begins again

Convection currents are responsible for radiators and onshore/offshore breezes. 

Energy Transfer by Heating - 1.6 Evaporation and Condensation

Evaporation

The process of a liquid turning into a gas. Takes place because the most energetic liquid molecules escape from the liquids surface and enter the air. The average Kinetic energy of the remaining molecules is less so the temperature of the liquid decreases; evaporation causes cooling. It is increased by -

• Increasing the surface area of a liquid
• Increasing the temperature of a liquid
• Creating a draught of air (breeze) across the liquids surface. 

Condensation

The process of a gas turning into a liquid.Takes place on cold surfaces. It is increased by -

• Increasing the surface area of the cool surface.
• Reducing the temperature of the cool surface.

Energy Transfer by Heating - 1.7 Energy Transfer by Design

The bigger the temp. difference between an object and it's surrounding area the greater the rate at which energy is transferred. It also depends on

• Materials the objects in contact with
• The objects shape
• The objects surface area. 

To maximise the rate of energy transfer we would

• Use good conductors
• Painted matte black
• Have maximised air flow surrounding them

To minimise the rate of energy transfer we would

• Good insulators
• White and shiny materials
• Prevent convection currents by trapping air in small pockets

Energy Transfer by Heating - 1.8 Specific Heat Capacity

Specific Heat Capacity - The amount of energy required to raise 1kg of a substance by 1                                         degree Celsius. Every substance has a different S.H.C. The greater                                           the S.H.C. the more energy required to raise temp. For example -

• Aluminium = 900 J/kg˚C 
• Copper = 490 J/kg˚C
• Water = 4200 J/kg˚C

EQUATION

Energy (J) = Mass (kg) x S.H.C (J/kg˚C) x Temperature Change (˚C)

E = m x c x θ

Energy Transfer by Heating - 1.9

People can reduce the rate of energy transfer leaving their house (and thus save money from fuel bills) by fitting -

• Fibreglass Loft Insulation to redue energy transfer by Conduction
• Cavity Wall Insulation that traps air in small pockets to reduce energy transfer by Convection
• Double Glazing to reduce energy transfer by Conduction through the windows.
• Draught Proofing to reduce energy transfer by Convection
• Aluminium Foil behind radiators to reflect Infrared Radiation back into the room

U-Values

This tells us how much energy/second passes through. Knowing the U-Values of materials means we can compare. The lower the U-Value the better the material is at insulating.

Solar Heating Panels - Contain Sun radiated heated water.This is used to heat up buildings or provide hot water. Positive- No fuel, so cheap to run. Negative - Expensive to install, don't work at night. 

Using Energy - 2.1 Forms of Energy

Potentials are stored energy forms.

• Energy can be transferred from one form to another
• Any object above the ground has gravitational potential energy.
• A falling object transfers gravitational potential energy into Kinetic energy.

Light - the sun, a lamp, an electrical appliance with a lit screen, a candle

Sound - a musical instrument, two objects colliding

Heat - any electrical appliance switched on, the sun, radiator

Potential - Gravitational (an object above ground), Elastic (compressed spring), Chemical (food)

Electrical - Electrical circuit, a live wire, any electrical appliance switched on

Nuclear - Nuclear power plant, radioactive materials

Kinetic - any moving object

Using Energy - 2.2 Conservation of Energy

YOU CANNOT CREATE OR DESTROY ENERGY. YOU CAN ONLY TRANSFER IT.

Conservation of Energy - Stated above. It means the total amount of energy always stays the                                           same. It applies to all energy transfers. 

Examples

1) When an object falls, Gravitaional Potential energy is converted into Kinetic Energy.

2) When an elastic band is stretched, Chemical Energy is converted into Elastic Potential Energy.

3) A Solar Cell tranfers Light Energy into Electrical.

4) A swinging Pendulum converts Gravitational Potential Energy into Kinetic Energy and back again if it is set in motion. 

Using Energy - 2.3 Useful Energy 

Machine - Something that transfers one form of energy to another. The energy we get out of it                        can either be useful energy or wasted energy. 

Useful Energy - Energy which is transfered to the place we want in the form we want it.

Wasted Energy - Energy which is not usefully transferred

Both forms of energy will eventually be transferred to the surroundings causing a rise in temperature. As it spreads out it becomes increasingly difficult to use for further transformations.

Energy is often waste due to heat which causes unnecessary heat. 

Sometimes friction can be useful though e.g brakes of a car or bicycle. Some of the kinetic energy is tranferred into heat energy that warms up the brakes. 

Using Energy - 2.4 Energy and Efficiency 

All forms of energy have the unit J for Joules. 

Input Energy - The energy supplied to a machine. 

Input Energy = Useful energy transferred + wasted energy

The less wasted energy, the more efficient a machine. 

Efficiency = Useful energy transferred     (x100)

          Total energy transferred to appliance

No appliance is 100% efficient, except an electric heater.

Sankey Diagrams are used to demonstrate the energy transfer through an electrical appliance. 

Electrical Energy - 3.1 Electrical Appliances

Electrical Appliances - These transfer electrical energy into the energy we require. Examples                                           include

• Lamps. Convert Electrical Energy into Light Energy
• Electric Mixers. Electrical Energy into Kinetic Energy
• Speakers. Convert Electrical Energy into Sound Energy
• Televisions. Convert Electrical Energy into Light and Sound Energy.

Many transfer energy by heating. Many times this is a useful transfer (e.g. Kettle) however often this creates wasted energy. Appliances should be designed to waste as little energy as possible. 

Well thats all folks. 

Electrical Energy - 3.2 Electrical Power

Power - The rate at which an object transfers energy. The unit of this is the Watt (W). An                          appliance with a power of 1 W transfers 1 Joule of energy per second. Often Watts are                  too small to use so we convert it to the Kilowatt (kW). 1kW = 1000 W.

EQUATIONS!!!!! Duh duh duh duh duh duuuuh (Darth Vadar theme tune) 

Power (W) = Energy (J)

                  Time (s)

P = E

       t

Efficiency = Useful Power Out     (x100%)

                                                            Total Power In 

Electrical Energy - 3.3 Using Electical Energy

Companies that produce mains electricity charge in kW h (Kilowatt Hour) units because the Watt is not suitable. 

A Kilowatt Hour is the amount of energy that is transferred by a one kilowatt appliance for an hour. 

EQUATION!!!!  (fan fare) 

Energy Transferred ( kW h) = Power (kW) x Time (h)

E = P x t

Electricity Meter - Records the amount kW h of energy used. If the previous meter reading is                                    used between the readings can be calculated.

Total Cost = Number kW h x Cost per kW h

Electrical Energy - 3.4 Cost Effectiveness Matters

Different number of costs we mst compare include -

• The cost of buying the appliance
• The cost of installing the appliance
• The running costs
• The maintenance costs
• The environmental costs
• The Interest Charged on a loan to buy the appliance

To reduce the energy bills you can buy more efficient appliances. These will reduce the amount of energy wasted. You could also install materials designed to reduce the energy wasted (loft insulation)

Payback Time = Time Taken for Appliance to pay for itself in terms of energy savings. 

Look at diagram of House on p15. 

Generating Electricity - 4.1 Fuel for Electricity

Water is Heated to turn a turbine (steam). The turbine is coupled with an electrical generator that produces electricity. 

The energy could come from burning a fossil fuel (coal, gas, oil), or it can be turned by steam directly.

Biofuels - Any fuel obtained from recently living or living organisms. Most are used in small-                    scales. They are renewable. 

Nuclear Power Stations

 The fuel is used is Uranium (sometimes Plutonium). The Uranium atom undergoes Nuclear Fission which releases energy. There are lots of nuclei so lots of energy is made. This energy is used to heat the water and produce the steam. These are much more powerful than Fossil Fuels and don't produce Carbon Dioxide but they leave behind radioactive waste which must be carefully stored for a long time. 

Generating Electricity - 4.2 Energy from the Wind and Water

Wind

• 
  We can use both wind and water to turn turbines directly
• In a wind turbine the wind passes through a propellor causing it to rotate. THis is connected to the generator and causes it to work.

Water

• Hydro-electric Power. Water is collected in a reservoir. This water is allowed to flow downhill and turn turbines at the bottom of the hill. With a pumped storage system surplus electricity is used to pump the water bafck uphill so it can be re-used.
• Wave Power. The wave movement drives a floating turbine that turns a generator. A cable delivers the electricity to the shore. 
• Tidal Power. A barrage is built across a river estuary causing a rising tide to be trapped behind it. When the water is released it drives the turbines. 

Generating Electricity - 4.3 Power from the Sun and the Earth

Sun

• Solar Energy. Travels through space as electromagnetic radiation. A solar cell can transfer this energy into electrical energy. Each cell only transfers a small amount of electricity . We can join cells to make Solar Panels. Water flowing through a Solar Heating Panel is heated directly by the Sun.
• Solar Power tower uses 1000's of mirrors to reflect sunllight onto a water tank and produce steam.

Earth

• Geothermal Energy. Produced inside Earth by radioactive processes. Heats surrounding rock. In volcanic areas, very deep holes are drilled and cold water is pumped down to the hot rocks. Here it is converted into steam. THis steam drvies turbines.Geyser's can also be used to drive turbines directly. 

Generating Electricity - 4.4 Energy and the Environment

• Coal, gas, oil = Non-renewable. The rate at which they are being used up is much bigger than the rate they are being produced.
• Oil and gas will run out in the next 50 years. Coal not much longer after that.
• Renewable sources can not run out. 
• Scientists are trying to look at ways to produce fuel and electricity with minimal damage to the environment. For example, Sulphur can be removed from fuel before being burnt and producing toxic gases. Carbon Dioxide can be sstoored in old oil/gas fields instead of being released. 
• All energy sources have advaantages/disadvantages. 

LOOK AT DIAGRAM TABLE ON P20 AND LEARN IT OFF BY HEART.

Generating Electricity - 4.5 The National Grid

The National Grid distributes Electricity in Great Britain. This is a grid network of pylons and cables that connect power stations to homes, schools, factories etc. Power stations can be switched in and out of the grid accordingly. 

The National Grid voltage = 132 000V. Power stations produce 25 000V

The Process

• Before leaving the factory, voltage is increased by a step-up Transformer. THis is because transmission at high voltage and low current reduces the energy wasted making it more efficient.
• It travels in thick over-head cables across country.
• At local sub-stations, a step-down transformer is used to lower the voltage back to it's original rate. The cables go underground and are distributed between homes. 

Generating Electricity - 4.6 Big Energy Issues

Base Load Demand - A constant supply of energy from coal, oil and nuclear power stations. This varies between season and time of day. 

     This variable deman is met using gas-fired stations, pumped storage schemes and renewable enrgy sources. 

    When demand is low, energy is stored by pumping water to the top reservoir of pumped storage systems. 

Start-up times - The time taken to start up a power station. Gas are very quick. Nuclear takes the longest.

LOOK AT TWO DIAGRAMS ON p 22

Waves - 5.1 The Nature of Waves

Waves are used to  transfer energy and information. 

Transverse Wave

The oscillation (vibration) of the particles is perpendicular to the direction in which it travels. (up and down waves) e.g. sea waves. 

Longitudinal Wave

The oscillation is parallel to the direction of travel. (squash stretch waves). e.g slinky.

Electromagnetic Waves

No moving particles in an electromagnetic wave. These are oscillations in the electric and magnetic field. They are transverse waves.

Mechanical Waves

Must travel through a medium (substance) so they involve particles. They can be either transverse or longitudinal. Waves on springs or sound waves. 

Waves - 5.2 Measuring Waves

Amplitude - The height of a wave crest or the depth of a wave from position of rest. Greater the                        amplitude the higher the amount of energy

Wavelength - The time taken for one complete wave. 

Frequency - The number of complete waves in one second. The unit is the Hertz (Hz) which is                         equivalent to /s.

EQUATION!!!! (Darth Vadar music)

Speed (m/s) = Frequency (Hz) x Wavelength (m)

v = f x λ 

These rules apply to both Transverse and Longitudinal Waves. 

Longitudinal - Wavelength = One compression to the next compression. or one rarefaction to                                              the next rarefaction. 

                     Frequency  = The number of compressions er second.

Waves - 5.3 Wave Properties: Reflection

The image in the mirror is due to reflection of light.

    On a plane mirror the Normal is an invisible line perpendicular to the mirror surface, positioned where the incident ray hits the mirror.

    Incident ray is the is the ray that goes towards the mirror. The reflected ray is the ray that goes away. The angle of incidence is is the angle bewteen incident ray and normal. The angle of reflection is the angle between the reflected ray and the normal. Both angles are equal. 

Image - 

• Same size as object
• Upright
• Virtual
• Same distance behind the mirror as the object is in front

Real Image - An image that appears on a screen because the light rays that produce it can                          pass through it. 

Virtual Image - An image that cannot be formed on a screen because the rays of light that                              produce the image only appear to pass through it. 

Waves - 5.4 Wave Properties: Refraction

Waves change speed when they change medium. Wave length changes but frequency stays the same.

The change in speed causes a change in direction. Refracion occurs in all waves, but light is the most obvious. 

Less dense, to more dense - refracted towards the normal. Slows down

More dense to less dense  - refracted away from the normal. Speeds up

Along the normal - no refraction, only a change in speed.

Different colours in white light have different wavelengths so they refract at different rates - this is called dispersion.

Violet is refracted the most, and red the least

Waves - 5.5 Wave Properties: Diffraction

Diffraction - The spreading of waves when they pass through a gap or around an                                         obstacle. Characteristic of all waves. The effect is most noticeable if the gap is                          the same size as the wavelength. 

TV Signals on hilly areas, radio signals on hilly areas. 

Waves - 5.6 Sound

Sound - Caused by mechanical vibrations and travels via Longitudinal wave. Tavels through all three states of matter. Travels best in Solids due to compact particles. 

Sound cannot travel through a vacuum in space due to a lack of particles. 

The Human ear can hear from 20Hz to 20,000Hz however this declines with age. 

Sound waves can be reflected to create echoes - 

• Only hard, flat surfaces suchas flat walls and floors reflect sound
• Soft things like carpets, curtains and furniture absorb sound
• An empty room sounds different once the above have been placed in it. 

Sound waves can be refracted. Refraction takes place at the boundaries between layers of air at different temperatures. Soudn waves can also be diffracted. 

Waves - 5.7 Musical Sounds

Pitch - This depends on the frequency of the sound wave. Higher the frequency, the higher the                  pitch.  

Loudness - This depends on the amplitude of the sound waves.

These differences above can be shown on an oscilloscope. 

• Tuning forks produce pure waveforms
• The quality of a note depends on the waveform
• Different instruments produce different waveforms, hence why they sound different
• Vibrations in a played instrument are what produce the sound waves. 
• In some instruments(e.g flute) a vibrating column of air is what produces the sound. 

Electromagnetic Waves - 6.1 The Electromagnetic Spectrum

Electromagnetic Radiations - These are electric and magnetic disturbances. They travel                                                  as waves and move energy from one place to another. All                                                  electromagnetic waves can travel through space at the                                                      same speed but they have different wavelengths and                                                          frequencies

Gamma         x-rays        Ultraviolet      V.Light      Infrared         Microwaves        Radio

• Gamma rays have the shortest wavelength/highest frequency
• Radio waves have the longest wavelength/lowest frequency
• Gamma Rays = 0.000 000 000 000 001 m
• Radio Waves = 10,000 m 
• All electromagnetic waves can travel through space at aspeed of 300 million m/s.

V = f x λ

Electromagnetic Waves - 6.2 Light, Infrared, Microwave and Radio Waves

Visible Light

• The only part of the Electromagnetic Spectrum the human eye can detect.
• We see the different wavelengths as different colours
• The wavelength increases from violet - red. White length is a mixture of all the colours.
• It can be used for photography

Infrared 

• Given out by all objects
• the hotter the object, the more it emits.
• Remote controls use IR Waves.
• Absorbed by skin, too much and it will burn

Microwaves

• Microwave transmitters produce wavelengths that can travel through the atmosphere. They are used to signals between satellites and Earth.
• Penetrate your skin and absorbed by body tissue. Can heat and damage internal organs

Radio

• Transmit radio and TV programs and carry mobile signals.

Electromagnetic Waves - 6.4 The Expanding Universe

The Doppler Effect

• A moving object heading towards you. If it emits a sound, the waves will be squashed. 
• If it moves away from you, the sound waves will be stretched.
• This causes a change in pitch we call The Doppler Effect.

Galaxies

• Galaxies are constantly moving. All Galaxies emits light.
• Red-shift means the Galaxy is moving away from us. This is because the wavelength will have increased so on the visible light spectrum (since red has a large wavelength) it will appear red.
• Blue-shift means the Galaxy is coming towards us. This is because the wavelength will have decreased so on the visible light spectrum (since blue has a smaller wavelength) it will appear blue. 
• All the Galaxies in the universe are moving away from each other so  the whole universe is expanding. 

Electromagnetic Waves - 6.5 The Big Bang

Red-shift gives us evidence that the universe is expanding in all directions

If it is now expanding then it suggests it started with a massive explosion at a very small initial point. This is known as The Big Bang Theory. *Our whole universe was in a hot, damn ... *

If the universe started with a Big Bang Explosion then high energy Gamma radiation would have been produced. As the universe expanded this would have become lower-energy radiation. 

Scientists discovered microwaves comeing from every direction in space. This is: 

Cosmic Microwave Background Radiation (CMBR)

The Big Bang Theory is the only explanation for all of these waves.