Physics - Energy
- Created by: Issy.ryan
- Created on: 23-12-17 13:59
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- Physics - Energy
- Energy Changes
- Kinetic Energy = 0.5 x mass x (speed)² (E????=½mv²)
- Gravitational Potential Energy = mass x gravitational field strength x height (E????=mgh)
- Elastic Potential Energy = 0.5 x spring constant x (extension)² (E????=½ke²)
- Specific Heat Capacity and Internal Energy
- Internal energy is the total kinetic and potential energy of all the particles that make up a system.
- Doing work on a system, heats it, which changes energy stored in the system and the energy of the particles within it. As energy increases, it will increase the temperature or produce a change in state.
- The temperature increase depends on; - the mass of the substance heated - what the substance is. - the energy input
- The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kg of the substance by 1?.
- change in thermal energy = mass x specific heat capacity x temperature change (?E=mc?????)
- Energy Transfers
- In energy transfers; - energy can be transferred usefully, stored or dissipated (spread out to surroundings). - energy cannot be created or destroyed
- In a closed system, the total energy never changes but it can be transferred from one store to another.
- Wasted energy is caused by unwanted energy transfers and is no longer available for useful transfers.
- Unwanted transfers can be reduced by; - lubrication, to reduce friction that produces heat - tightening any loose parts, prevents unwanted vibration (sounds). - thermal insulation, reduces heat loss.
- The rate of cooling in a building depends on the thickness and conductivity of the walls.
- In energy transfers; - energy can be transferred usefully, stored or dissipated (spread out to surroundings). - energy cannot be created or destroyed
- National and Global Energy Resources
- The main uses for energy resources are transport, electricity generation and heating.
- All energy resources are either renewable (can be replenished) or non-renewable (will eventually run out).
- Biofuel = renewable, used for transport and electricity generation. Large areas of land are needed for growing fuel crops , at the expense of food crops for poorer places.
- Wind = renewable, used for electricity generation. Doesn't provide a constant source of energy, turbines can be noisy./dangerous for birds, they're also unattractive in the countryside.
- Water (hydro-electricity) = renewable, used for electricity generation. Requires large areas of land to be flooded, altering ecosystems and displacing locals.
- Geothermal = renewable, used for electricity generation and heating. Only available in limited areas where hot rocks close to surface are found e.g Iceland.
- Tidal = renewable, used for electricity generation. Tides unreliable, affect output. Expensive to build, alters habitats and causes problems for shipping.
- Solar = renewable, used for electricity generation and some heating. Depends on light intensity, so no power made at night. Expensive compared to output.
- Water-waves = renewable, used for electricity generation. Output depends on waves, so is unreliable. Can alter habitats.
- Nuclear-fuel = non-renewable, used for electricity generation and some military transport. Produces radioactive waste, but no other emissions. Expensive to build and decommission, reliable output.
- Coal = non-renewable, used for electricity generation, heating and some transport. Burning produces greenhouse gases (CO? and acid rain, SO?). Reliable output.
- Oil = non-renewable, used for transport and heating. Reliable output, provides a compact energy source for transport. Burning produces CO?, NO? and SO?. Serious environmental damage if spilt.
- Gas = non-renewable, used for electricity generation, heating and some transport. Reliable output, burning produces CO? but not SO?.
- Energy Changes
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