GCSE Physics 1B - Electricity and Waves

Energy Sources

There are 12 different types of energy resources, that are either renewable or non-renewable.

Non-Renewable

-Coal

-Oil

-Gas

-Nuclear fuels (uranium and plutonium)

Non-renewable fuels will all run out one day. They damage the environment, but are effective therefore provide most of our energy.

Renewable

-Wind

-Solar

-Hydroelectric

-Wave

-Tidal

-Geothermal

-Biofuel

-Food

Renewable energy sources will never run out. They damage the environment, but not nearly as much as non-renewable sources. However, renewable sources are unreliable as they depend on the weather, and do not provide as much energy.

Power Stations

Energy sources can be burned to drive turbines in power stations. Most of the electricity we use is generated from the four NON-RENEWABLE sources of energy, in big power stations. 

Basic features of a typical power station:

1) The FOSSIL FUEL is BURNED to convert its stored CHEMICAL energy into HEAT / thermal energy

2) The heat energy is used to HEAT WATER (or sometimes air) to produce STEAM.

3) The steam turns a TURBINE, converting heat energy to KINETIC energy.

4) The turbine is connected to a GENERATOR, which transfers kinetic energy into ELECTRICAL energy.

diagram

Wind Power

Advantages:

-They cause no pollution.                                                                                                      -There are no fuel costs and minimal running costs.                                                           -No permanent damage to the landscape.  

Disadvantages:

-Spoil the landscape/view.                                                                                                     - Initial costs are high.                                                                                                            -No power when the wind stops.                                                                                           -Very noisy

Solar cells

Advantages:

-help remote places                                                                                                               -no pollution                                                                                                                           -energy is free, running costs are close to 0                                                                        

Disadvantages:

-Only work in the daytime.                                                                                                     -Initial costs are high                                                                                                              -only work on a small scale.                                                                                                 -sometimes unpractical or too expensive to connect to the national grid.                

Hydroelectric power

Advantages:

-No pollution                                                                                                                           -reliable                                                                                                                                  -no fuel and minimum running costs                                                                                    -useful in remote places                                                                                                       

Disadvantages:

-requires flooding of a valley by building a dam                                                                     -initial costs are high                                                                                                              -loss of habitat for species due to flooding

Wave power

Advantages:

-no pollution                                                                                                                           -no fuel costs, low running costs                                                                                          -useful on small islands

Disadvantages:

-need to be around the coast                                                                                                -spoil the view                                                                                                                       -hazardous to boats                                                                                                              -fairly unreliable                                                                                                                     -high initial costs

Geothermal energy

Geothermal Energy

Advantages:

-free energy                                                                                                                           -no environmental problems

Disadvantages:

-there aren't many suitable locations for power plants                                                         -the cost of of building power plants is high compared to the amount of energy we use

Biofuels

Advantages: 

-can be used in cars                                                                                                              -can be solids, liquids or gases                                                                                            -can be made from fossil fuels or recently dead organisms

Disadvantages:

-the burning process releases pollution into the atmosphere.

Carbon Capture

Carbon capture and storage is used to reduce the amount CO2 building up in the atmosphere and reduce the strength of greenhouse gases.

It works by collecting the carbon dioxide from power stations before it is released.

The captured CO2 can then be pumped into empty gas and oil fields (e.g under the sea)

CCS (carbon capture and storage) is a new technology that is developing fast, and new ways to store CO2, and the stored CO2 can be used to produce oil for biodiesels. 

Environmental Issues:

Atmospheric pollution - coal, oil, gas

Visual pollution - coal, oil, gas, nuclear, tidal, wave, wind, hydroelectric

Using up resources - coal, oil, gas, nuclear

Noise pollution - coal, oil, gas, nuclear, wind

Disruption of habitats - hydroelectric, tidal, biofuels

Disruption of leisure activities - waves, tidal (boats)

Other problems - nuclear (dangerous waste, explosions) hydroelectric (dams burst)

National Grid

We DO NOT want power stations in town because of:

-pollution and it's health effects

-transportation of fuel

-use of land 'visual amenity'

We DO want an assured supply of electricity : 

-no technical faults

-routine maintenance

THE NATIONAL GRID IS A NETWORK OF CABLES AND TRANSFORMERS USED TO DISTRIBUTE ELECTRICITY FROM POWER STATIONS.

The AMPLITUDE is the displacement from the rest position to the crest (half)

The WAVELENGTH is the length from one crest to the next

The FREQUENCY is the number of complete waves passing a certain point per second OR the number of waves produced by a source each second. Measure in Hertz - Hz. 

1 Hz is 1 wave per second

Most waves are TRANSVERSE:

- light and all other EM waves

-ripples on water

-waves on strings

IN TRANSVERSE WAVES THE VIBRATIONS ARE PERPENDICULAR (AT 90 degrees) TO THE DIRECTION OF ENERGY TRANSFER OF THE WAVE.

VIBRATIONS GO FROM SIDE TO SIDE

Examples of LONGITUDINAL waves:

-sound waves and ultrasound

-shock waves

IN LONGITUDINAL WAVES THE VIBRATIONS ARE PARALLEL TO THE DIRECTION OF ENERGY TRANSFER OF THE WAVE.

VIBRATIONS GO IN THE SAME DIRECTION AS THE WAVE IS TRAVELLING.

Period = wavelength

SPEED = FREQUENCY X WAVELENGTH

 (m/s)                    (Hz)                                   (m)

OR

V = f x λ

velocity = frequency x lambda (wavelength)

ALL WAVES can be REFLECTED, REFRACTED and DIFFRACTED

Reflection

Reflection of light allows us to see objects. Light bounces off them into our eyes.

When light travelling in the same direction reflects from an UNEVEN surface, such as a piece of paper, the light reflects off at different angles. 

When light travelling in the same direction reflects from an EVEN surface, (like a mirror) then it's all reflected at the same angle and you get a clear reflection.

The LAW OF REFLECTION applies to EVERY REFLECTED RAY:

ANGLE OF INCIDENCE = ANGLE OF REFLECTION

Refraction

Waves go through a new material but CHANGE DIRECTION.

1) When a wave crosses a boundary between two substances, it changes direction.

2) When light shines on a glass window pane, some of the light is reflected, but a lot of it passes through the glass and gets refracted as it does so.

3) Waves are only refracted if they meet a new medium at an angle. 

4) If they're travelling along the normal (i.e the angle of incidence is zero) they will change speed, but are NOT refracted - they do not change direction.

Diffraction

The waves 'bend round' obstacles, causing the waves to spread out.

1) All waves spread out - diffract, at the edges when they pass through a gap or pass an obstacle.

2) The amount of diffraction depends on the size of the gap relative to the wavelength of the wave. 

The NARROWER the GAP or the LONGER the WAVELENGTH, the MORE the wave SPREADS OUT.

3) A narrow gap is one that is the same order of magnitude as the wavelength of the wave (they are about the same size)

Light has a very SMALL wavelength, so it can be diffracted, but needs a very small gap

Total Internal Reflection has been used in periscopes, binoculars and cameras.

Total Internal Reflection makes optical fibres work. The light keeps reflecting from the inside surface until it leaves the other end of the fibre. 

An endoscope is a piece of medical equipment that is a tube used to look into someones stomach through their mouth. This uses optical fibres.

The order of the electromagnetic spectrum = 

-radio waves

-micro waves

-infra red

-visible light

-ultra violet

-x rays

-gamma rays

Rock Music Is Very Useful for eXperiments with Goats

Radio Waves

Radio Waves are used mainly for COMMUNICATION.

Radio waves are EM radiation with wavelengths longer than 10cm.

*Long - wave radio (1-10km) can be transmitted from London and received halfway round the world, because long wavelengths DIFFRACT.

*Long - wave radio wavelengths can also diffract around hills and into tunnels etc.

-Radio waves used for TV and FM radio are short wavelengths as the transmitter has to be in sight.

Micro waves

Micro waves are used for a satellite communication and mobile phones.

Infrared Waves

Infrared Waves are used for remote controls and optical fibres.

Visible Light

Visible light is useful for photography.

Sound Waves

Sound waves are caused by vibrating objects.

They are a type of LONGITUDINAL wave. 

Sound waves can REFLECT and REFRACT. 

They are reflected by hard, flat surfaces, and the reflection can be an echo.

The HIGHER the FREQUENCY, the HIGHER the PITCH.

kHz = kilohertz.                         mHz = megahertz.

ALL ELECTROMAGNETIC WAVES TRAVEL AT 300,000,000 m/s.

Below visibilty = INFRA RED.

-lower frequency.

-infra red is heat radiation.

-used in: cooking, heating, finding people.

-seen by some reptiles.

Above = ULTRA VIOLET

-higher frequency.

-dangerous, damages skin cells and can lead to cancer.

-used in: security(false money) killing bacteria.

-seen by many insects, and some short lived mammals and birds.

Analogue

the use of continuously changing quantities to represent numbers.

Digital

information represented by numbers or as a series of discrete numbers.

THE LONGER THE WAVELENGTH, THE GREATER THE EFFECT OF DIFFRACTION OVER AND BETWEEN HILLS AND BUILDINGS!

Diagram;

THE UNIVERSE IS EXPANDING.  

Light from other galaxies is Red-Shifted.

-different elements absorb different frequencies. Each element produces a specific pattern of dark lines at the frequencies that it absorbs in the visible spectrum.

-When we look at light from distant galaxies, we can see the same patterns, but at slightly lower frequencies than they should be - they're shifting towards the red end of the spectrum. We call this red shift!

THE FURTHER AWAY A GALAXY IS, THE GREATER THE RED SHIFT.

The Doppler Effect

1) When something that emits waves moves towards you or away from you, the wavelengths and frequencies of the waves seem different - compared to when it is stationary.

-The frequency of something moving towards you will seem higher and its wavelength will seem shorter.

-The frequency of something moving away from you will seem lower and its wavelength will seem longer.

The Doppler Effect happens to both LONGITUDINAL and TRANSVERSE waves.

The further away a galaxy is from the earth, the faster they're moving away.

The Big Bang happened approximately 14 billion years ago.

Just after the Big Bang, while the universe was still extremely hot, everything in the Universe emitted very high frequency radiation.

As the Universe expanded it has cooled, and this radiation has dropped in frequency and is now seen as microwave radiation.

The Steady State theory is the theory that the Universe has always existed as it is now, and will always do.

The Big Bang Theory will be explains the universe's expansion, but does not explain what actually caused the explosion, or what conditions were like before the Big Bang.