energy summary

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  • Created by: Hemdev
  • Created on: 09-11-16 18:13
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  • ENERGY
    • ENERGY STORE
      • Thernal energy store
      • Kinetic energy store
      • Gravitational potential energy store
      • Elastic Potential Energy store
      • Chemical energy store
      • Magnetic energy store
      • Electrostatic energy store
      • Nuclear enrgy store
    • SYSTEM
      • A system an object or group of object working together. When a system changes, energy is transferred. It can be transferred into or away from the system, between different objects in the system or between different types of energy stores
        • Closed systems are systems which neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always 0
    • WORK DONE
      • In a collision between a car and a stationary object, the normal contact force between the car and the object does work. It causes energy to be transferred from the car's kinetic energy store to other energy stores, e.g. the elastic and the thermal energy stores of the object and the car body. Some enrgy might also be transferred away by sound waves.
    • Kinetic and Potential energy stores
      • When energy is transferred to the kinetic energy store when the object speeds up and is transferred away from this store when an object slows down
      • Equation for gravitational potential energy:
        • GPE=mgh
          • height (m)
            • x
              • gravitational field strength (or 'g') (N/kg)
                • x
                  • mass (kg)
                    • GPE (J) =
      • When you compress a string, energy is transferred into the elastic potential energy store
        • Equation: PEspring = 0.5 • k • e^2
          • where k = spring constant
          • x = amount of compression (relative to equilibrium position)
    • SPECIFIC HEAT CAPACITY
      • Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1*c
      • More energy needs to be transferred to the thermal energy store than others. This means that materials that need to gain lots of energy in their thermal energy stores to warm up also transfers loads of enegy when they cool down
      • Specific heat capacity experiment
        • 1) Place a Joule heater in the 1Kg lead block and connect it to a power supply
          • 2) Put a little bit of glycerol on the thermometer (this makes the temperature reading more accurate) and place it in the 1Kg lead block.
            • 3) Switch the power supply on and count the number of flashes that occur while the temperature changes by 1 degrees C.
              • 4) Each flash on the Joulemeter is 100J.
                • 5) You can calculate the specific heat capacity: specific heat capacity = Energy/ (mass x temperature change)
                  • 6) Repeat with Aluminium block.
    • CONSERVATION OF ENERGY AND POWER
      • Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
      • power=energy transferred/ time
        • W=J/s
      • power= work done/ time
        • W=J/s
    • REDUCING UNWANTED ENERGY TRANSFERS AND IMPROVING EFFICIENCY
      • Thermal conductivity is a measure of how quickly energy is transferred through a material in the way of conduction. Materials with a high thermal conductivity transfer energy between their particles quickly
      • You can reduce unwanted energy transfer in a machine with moving components, the use of lubricants can be used to reduce the friction between the object's surfaces when they move
      • Preventing unwanted energy transfers at home
        • cavity walls
        • loft insulations
        • double-gazed windows
        • draughr excluders
      • Experiment
        • 1) boil water in a kettle. pour some of the water into a sealable container (e.g. a beaker and a lid) to a safe level. measure the mass of the water in the container
          • 2) use a thermometer to measure the intial temperature of the water
            • 3) seal the container and leave it for 5 mins. measure this timing using a stopwatch
              • 4) remove the lid and measure the final temperature of the water
                • 5) pour away the water and allow the container to cool to room temperature
                  • 6) repeat this experiment, but wrap the container in a different material (e.g. newspaper, foil) once it has been sealed. make syre you use the same mass of water each time
      • efficiency of an energy transfer
        • The ratio of energy which was transferred to a useful form compared to the total energy initially supplied is called the efficiency of the device.
        • efficience=
          • useful output energy transfer (or) power
            • /
              • total input energy transfer (or) power
    • ENERGY RESOURCES AND TRENDS IN THEIR USE
      • Renewable resources
        • The Sun
        • Wind
        • Water waves
        • Hydro-electricity
        • Bio-fuels
        • Tides
        • Geothermal
      • The difference between renewable and non-renewable energy resources is that renewable resources are infinite in supply. This resource type can renew itself. Non-renewable resources are finite--eventually, if they are used up, there will be none left

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