Physics 1

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  • Created by: amreena
  • Created on: 18-01-13 17:48

Kinetic Theory

Solids

  • Close together
  • Regular pattern
  • Vibrate

Liquid

  • Close together
  • Random
  • Move around each other

Gases

  • Far apart
  • Random
  • Fast movers in any direction
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Conduction

Metals are good conductors of thermal energy.

Non-metals and gases are usually poor conductors also known as insulators.


In a metals the electrons leave the atom. The new electron is called a free electron and the atom is now a charged ion.

The tightly packed ions vibrate and the kinetic energy created by the hot parts is transferred to the cool parts by the free electrons.The free electrons move through the surface and collide with the ions.

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Insulation

Insulation is keeping the heat inside an object.

When talking about insulating a house you should remember heat can be lost through many places.

Ways to stop heat loss in a house:

  • Roof-loft insulation
  • Windows-double glazing
  • Gaps around the door-draught excluders
  • Floor-carpet
  • Wall-cavity wall insulation
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Convection

Convection can only occur in fluids. Fluids are gases and liquids. When a fluid is heated, it rises and mixes with the rest of the fluid. The fluid circluates and cools then it falls.

This is a convection current:

(http://www.hk-phy.org/contextual/heat/hea/conve/convection_e.gif)

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Themal Radiation

  • Thermal radiation is energy transfer by electromagnetic waves.
  • Thermal radiation can also be known as infrared radiation.
  • All objects emit thermal radiation.
  • The hotter an object is, the more thermal radiation it emits.

If an object is dark and has a dull/matte surface then it will be a good absorber and emitter of heat.

If an object is light and has a shiny surface then it will be a poor absorber and emitter of heat.

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Vacuum Flask

Plastic cap-

Stops heat loss from the top.

Double walled plastic container-

Double wall creates vacuum preventing conduction/convection because no particles.

Silver surfaces-

Doesn't radiate heat but reflects back into flask.

Plastic Cover-

Protects inside glass from breaking.

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Evaporation and Condensation

Evaporation

Some particles in a liquid will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have less kinetic energy and dont have as much heat. This is why evaporation causes cooling. Evaporation occurs when the particles overcome the forces of attraction.

Condensation

It happens when a gas is in contact with something that is colder than itself and changes state from gas to liquid. It becomes more dense and that is why it is called condensation. 

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Boltzmann Distribution Graph

This is the Boltzmann Distribution Graph for evaporation.
(http://www.webchem.net/notes/how_far/kinetics/maxwel2.gif)

 

The shaded area represents the particles that have enought energy to evaporate and escape the liquid.

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Specific Heat Capacity

The specific heat capacity is the energy needed to raise the temperature of 1Kg of a material by 1°C. The units of specific heat capacity are J/Kg/°C.

Equation to calculate SHC:

SHC=Energy supplied/(mass*temperature change)

The SHC is dependant on the following:

  • the mass of the object
  • the substance the object is made from
  • the amount energy transferred to the object.
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Cost of Electricity

The amount of electrical energy used depends on two things. The power of the appiance. The time for which the appliance is working.

Electrical energy used=power*time

The utility company charges for units of electrical energy in units called kilowatts hours (KW/H).
(http://moosey.net/pet.png)

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Power Stations

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/smoke_chimneys.jpg)

Furnace-       Boiler heat is transferred into water and then creates steam.

Turbine-        Steam passes into the tank and spins the turbines.

Condenser-   Water from the steam goes into the condenser and is re-used.

Generator-     A shaft connected to the turbine. Spins a powerful magnet and turns the                             steam into electricity.

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Non-renewable

A non-renewable source of energy means that Coal oil and gas have something in common, they are fossil fuels which are nor-renewable sources of energy. Fossil fuels are made from the fossils of dead living things. They take a long time to be made, millions of years.

Advantages:

  • Concentrated
  • Easy to transport
  • Readily available
  • Cheap
  • Reliable

Disadvantages:

  • Non-renewable
  • Cause acid rain
  • Greenhouse effect
  • Limited supply
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Renewable

A renewable source of energy is something that you can get more of and is good for the environment. The renewable energy sources are wind, hydroelectric, biomass, solar, wave, geothermal, tidal.

Advantages:

  • Can never run out
  • Potential to make a lot of energy
  • Don't contribute to pollution

Disadvantages:

  • Relies on weather conditions
  • Can be expensive and costly
  • Sometimes its only good in certain places
  • Don't look good and has noise pollution
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Nuclear Power

3 Facts:

  • It has to be built near water but it cant be built near big cities because it causes radiation but not too far either-need customers
  • Uses a pressurise water reactor-a nuclear reactor that uses water as a coolant and moderator; the steam produced can drive a steam turbine.
  • Its very dangerous and can cause cancer

2 Advantages:

  • Produces a lot of energy
  • Can be used to kill cancer cells

2 Disadvantage:

  • Expensive to build
  • More animals exposed to the nuclear waste in the water
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National Grid

The electricity will go from the power station to the step up transformer which increases the voltage to make it travel efficiently. After it has gone through the pylons it will go to the step down transformer which will decrease the voltage to make it safe to use.

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Pumped Storage

Pumped Storage uses potential energy which comes from the top reservoir. This turns the turbines creating electricity. Some is stored for when there is a large demand so you can supply during the day and make it during the night.

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Waves

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/74_amplitude__wavelength.gif)

Amplitude- The loudness and the height of the wave. The bigger the amplitude, the louder the sound is.

Wavelength λ- This is the distance between two corresponding points on a wave. It is measured in metres.

Frequency- The number of waves per second. It is measure in Hertz-Hz. It measures pitch.

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Waves Continued

Longitudinal(top)- The waves move along in the same direction as the disturbance or vibration.

Transverse(bottom)- The waves move at the right angles to the disturbance or vibration.

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Electro-Magnetic Spectrum

Reflections

There are two types of mirrors, flat and curved. Flat mirrors are known as plane mirrors.If a mirror curves in, it is a concave mirror. If a mirror curves out, it is a convex mirror.

(http://www.daviddarling.info/images/plane_mirror_reflection.gif)

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Refraction

Towards (normal) Air Glass Away (from normal) Glass Air

Speed of light decreases in denser media.

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Ripple Tank

A ripple tank produces water waves that can be reflected, diffracted and refracted.The paddle generates waves by vibrating.

Reflected: Barrier

Diffracted: Barrier with a gap

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