Energy - Physics

Energy - Physics

1. Energy Stores + Systems

   • Types
     • Thermal
     • Kinetic
       • K=1/2m(v)squared
         • m=mass
         • v=speed
     • GPE
       • P=mgh
         • m=mass
         • g=gravity
         • h=height
       • air resistance causes energy to be transferred to other energy stores/types
         • no resistance = all into kinetic energy
     • EPE
       • E= 1/2k(e)squared
         • k=spring constant (N/m)
         • e=extension (m)
       • stretching/squishing an object
     • Chemical
     • Magnetic
     • Electrostatic
     • Nuclear
   • When an object changes energy is transferred in or away from it
   • Closed = matter nor energy can enter or leave
   • Transferred by heat or work done

2. Specific Heat Capacity

   • Change in thermal energy = m x c x temp change
     • m=mass(kg)
     • c = specific heat capacity (J/kgC)
   • warm 1kg of a substance by 1'C
   • Practical
     • Link: https://www.youtube.com/watch?v=jW2ANwnfsUY

3. Conversion of Energy and Power

   • P(W) = E/t
     • E=energy transferred (J)
     • t=time (s)
     • rate of energy
     • rate of work done
       • P(W) = Work done/time
     • One Watt = 1 joule of energy transferred per second
     • Powerful = large amount of energy in short amount of time
   • Energy can be transferred usefully, stored or dissipated but cannot be created or destroyed
     • Dissipated = waste of energy - gone into the surroundings

4. Conduction + Convection

   • Convection = liquids + gases only
     • particles move away from hotter to cooler
     • can move = when heated particles move apart = bigger spaces = less dense
     • can flow = warmer less dense will rise above denser, cooler regions
   • Conduction = mainly in solids
     • vibrating particles transfer energy to nearby particles
       • goes through objects then to surroundings
     • particles collide when heated causing energy to be transferred
     • Thermal conductivity = how quickly energy is transferred through a material
   • Reducing Unwanted Energy Tranfers
     • Insulation
       • Thick walls = low thermal conductivity
       • Cavity walls = gaps = less conduction
         • foam in gaps = still air but less so less convection
       • loft insulation = less convection
       • Double glazed windows = like cavity walls
       • Draught excluders = less convection
     • Practical
       • https://www.youtube.com/watch?v=RZfSA2Xa6SU
     • Lubricants reduce friction

5. Efficiency

   • Efficiency = Useful/Total
   • less energy wasted = more efficient
   • Improve: insulating, lubricating or making them more streamlined
   • No device is 100% efficient
     • Electric heaters are an exception - their job is to put energy into the environment in the form of heat
   • All energy normally ends up as thermal

6. Renewable and Non-renewable

   • Renewable Types
     • Sun/Solar
       • Heat + electricity
       • Expensive
       • No pollution
       • Reliable in daytime
       • Problem when high demand
     • Wind
       • No pollution
       • Noisy
       • Wind too strong or too little = problem
       • No permanent damage
       • Initial costs = high
     • Water Waves
       • Unreliable
       • Initial costs are high
       • Does not cost much to run
       • Suitable for small islands
       • Wave powered turbines connected to generators
     • Hydro-electricity
       • Requires flooding of a valley
       • Provides immediate response for an increased demand in electricity
       • No problem with reliability unless there is a drought
       • Useful on a small scale in remote areas
     • Bio-fuel
       • Vehicle transport
       • Electricity
     • Tides
       • Big dams - water allowed through turbines at controlled speed
       • No pollution
       • Alters habitat for wildlife
       • prevents free access for boats
       • Reliaable
         • Twice a day without fail
         • Sun and Moon
         • Height may be variable = low tides = less energy
       • Initial costs = moderately high
         • Not high running costs
         • No fuel costs
     • Geothermal
       • Possible in volcanic areas
         • Not many suitable locations
       • Brilliant energy that is reliable
       • Electricity + heat
       • Cost of building > amount of energy (at the start)
     • NEVER run out (renewed)
     • Don't provide much energy
     • Less 'nasty' to the environment
   • Non-Renewable
     • Coal
     • Oil
       • Petrol + diesel
     • Natural Gas
       • Heat
     • Most damage + most energy
     • WILL run out

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