P1 | Mapas Mentais

Energy Transfer
1. 3 methods of transfer are conduction, convection, radiation.
2. The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating.
3. Rate of transfer of energy depends on surface area and volume, object materials, surfaces.
Infrared Radiation
1. All objects emit and absorb infrared The hotter an object is, the more IR it emits in a given time (time is important!)
2. Dark, matt surfaces – good absorbers, good emitters (this means that a dark, matt object will heat up faster or cool down faster than a light, shiny one)
3. Light, shiny surfaces – poor absorbers, poor emitters, good reflectors.
Particles
1. Conduction, convection, evaporation and condensation all transfer energy, and all involve particles in their theories.
  1. Convection Takes place in liquids and gases. When a liquid or gas gets hotter, the particles have more KE they move around more, making the liquid or gas less dense. Therefore, hot liquids or gases will rise above cooler liquids or gases. (HEAT DOES NOT RISE, HOT LIQUIDS AND GASES DO!!)
  2. Conduction All to do with particles banging into each other and passing on KE. Metals have free electrons which can also pass on KE, making metals excellent conductors. The arrangement of particles in a substance determine how good a conductor it is.
2. In an object, the more kinetic energy the particles have, the hotter the object is.
3. Particle arrangements:
  1. Solid – fixed in place, least amount of KE but still some movement
  2. Liquid – some fixed arrangement, free to slide over each other, more KE than solid
  3. Gas – free to move about randomly, no fixed arrangement, lots of KE
Evaporation
1. Particles in a liquid are held together by forces
  1. The particles need lots of kinetic energy to overcome these forces
    1. Particles can gain kinetic energy through heating but that energy has to come from somewhere
      1. Liquids on your skin get the energy they need for evaporation from your skin.
        So your skin is losing energy through heating the particles and it will feel colder.
        If particles are leaving the liquid on your skin through evaporation, they are taking kinetic energy with them.
        The average kinetic energy of the liquid on your skin has dropped.
Heating and Insulation
1. Insulation materials aim to reduce energy transfer by heating – they may reduce conduction, convection, and radiation.
2. New heating systems or insulation for a house cost money. The payback time of an investment tells you how long it will take to get your money back based on how much the investment saves you.
  1. Payback time = initial investment / saving per year
3. Insulation materials for homes (including double glazing) are often given a U-value. This is a measure of how effective the insulator is. The lower the U-value, the better the material is as an insulator.
4. Liquids on your skin get the energy they need for evaporation from your skin.
5. Solar panels sometimes contain water that is heated by the Sun. The pipes in a solar panel are often black. The hot water can be used for heating.
Efficiency
1. You might need to rearrange these and put in the numbers. Answers can be given either as a percentage (e.g. 30%) or as a decimal (0.3) DO NOT combine these (e.g. 0.3%)
Generating Electricity
1. Power stations heat water to make steam steam turns a turbine  the turbine spins a generator
2. Heat can be generated by: burning fossil fuels nuclear fission burning biofuels
3. Water and wind can drive a turbine directly (no need for heating)
4. The Sun’s energy can be used to generate electricity (either by heating water or directly)
5. Different methods of generating have different effects on the atmosphere
6. Small-scale generation is useful in remote areas.
7. National grid – a grid of cables and transformers transferring electrical energy around the country
8. Step-up transformer voltage up, current down  lower current means less heating in cables  less energy wasted in the cables
9. Step-down transformer voltage down, current up  voltage is stepped down to a level which is safe to use in homes, factories, etc.
electrical energy
1. There are a few formulae you should be familiar with (some will be given to you in the exam).
2. Electrical appliances are machines, they transfer energy from one form to another. For example, a light bulb takes in electrical energy and gives out light and heat; a hair dryer takes in electrical energy and gives out heat, sound, and kinetic energy.
waves
1. Electromagnetic waves are transverse. Sound waves are longitudinal. Mechanical waves can be either.
2. Transverse Vibrations are perpendicular to the direction of energy transfer
3. Longitudinal Vibrations are parallel to the direction of energy transfer. Compressions – where the lines are close together. Rarefaction – where the lines are spread out.
4. Waves can be reflected, refracted (light changing direction), and diffracted (spread out – much greater diffraction when the obstruction or gap is a similar size to the wavelength)
5. angle of incidence = angle of reflection
6. v = f x λ
Electromagnetic spectrum
1. Electromagnetic waves form a continuous spectrum – the EM spectrum
2. Some of these EM waves can be used for communications: Radio waves – TV and radio (these can be diffracted by mountains) Microwaves – mobile phones and satellite TV Infrared – remote controls and optical fibres Visible light - photography
3. All EM waves travel at the same speed in a vacuum.
Big Bang Theory
1. Theories
  1. Other theories: There are other theories for the origins of the Universe. The Steady State theory suggests that the Universe has always been huge and is expanding because matter is entering the Universe through white holes. However, there is very little evidence for this theory.
  2. The Big Bang theory states that… Everything in the known Universe was contained at a very hot, very dense initial point. A rapid expansion took place around 13.7 billion years ago in which space, time and all matter were created. There are 2 key pieces of evidence for this theory – CMBR and Red-shift.
2. Cosmic Background Radiation
  1. If you look into space with your eyes, you will see a lot of emptiness. But if you use microwave detectors you will see a lot of cosmic microwave background radiation (CMBR). The existence of this radiation can only be explained by the Big Bang theory.
  2. The evidence for the Big Bang Theory
3. Red Shift
  1. is another piece of evidence that the Universe is expanding because it shows us that galaxies are moving away from each other.
Red Shift
1. Dopple Effect
  1. Doppler an object making a sound is moving away from you, the sound waves stretch out  wavelength increases, frequency decreases
  2. Doppler can also be applied to light, but the object emitting the light needs to be moving very fast and huge distances this is called Red-shift
2. Absorption Spectra
  1. These show which colours of light are absorbed by, for example, the atmosphere of a planet or the contents of a galaxy. The absorbed light is shown by dark lines on a colour spectrum. For a galaxy moving away from us, these lines are shifted towards the red end of the spectrum.
3. What is Red shift and blue shift
  1. Red Shift
    1. stretch out  wavelength increases, frequency decreases this has the effect of the effect is the colour of the wave changes ro the red
  2. Blue Shift
    1. Blue-shift is the opposite to red-shift. If a galaxy is moving towards us the wavelength of light reduces and the spectrum of light is shifted towards the blue part of the spectrum.
  3. The faster the star or galaxy moves the bigger the red shift will be
Formulae
1. Rearranging the Formulae
  1. if the equation is: X=YxZ
    1. if u were to make Y the subject of the formula then u would take the Y and take it underneath and this method works for the same to make Z the subject but you move the Y underneath
2. all of the formulas for P1 are given to you ( there are 5)

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	Criado por MUSICAL MATTHEW quase 9 anos atrás