Use of Energy - Physics

• Density = Mass / Volume
• Density of Regular Solids:

  1. Record mass via mass balance.
  2. Calculate volume (length×width×height).
  3. Use formula to calculate Density.
• Density of Irregular solids:

  1. Record mass with mass balance.
  2. Fill measuring cylinder with water and Record volume.
  3. Place object into measuring cylinder and Record volume.
  4. Calculate volume of object by volume with object - the start volume.
  5. Use formula to calculate density.
• Density of liquids:

  1. Record mass of empty measuring cylinder.
  2. Add liquid to the cylinder and Record volume.
  3. Record mass of cylinder with liquid.
  4. Calculate the mass of (cylinder + liquid) - mass of empty cylinder.
  5. Use formula to calculate the density.
• Types of Heat Transfer:

  Convection - The transfer of heat via the movement of particles in liquid and gases.

  Conduction - The transfer of heat through the vibration of particles in solids.

  Radiation - The transfer of heat via a wave emitted by hot objects.
• Hot air rises as it is less dense.
• Cold air sinks as it is more dense.
• • Particles pass energy during collisions.
  • Metals are good conductors due to their free electrons which boost rate of heat transfer.
• Convection Experiment:

  1. Fill beaker to 3/4 full of water.
  2. Use forceps to pick up a manganate and drop it to one side of the beaker.
  3. Light bunsen away from the apparatus and change to blue flame.
  4. Put flame directly underneath crystal and Record observations.
• Radiation Experiment:

  1. Use sellotape to attach a 2cm strip of black paper to the bulb of one thermometer.
  2. Do the same with silver foil.
  3. Clamp the 2 thermometer the same distance away from a filament lamp. (10cm)
  4. Record the temperature shown by the 2 thermometers.
  5. Switch lamp and Record again after 10 minutes.
• To prevent conduction use insulators such as foam or plastic.
• To prevent convection reduce the space for air to move.
• To prevent radiation use shiny metal to reflect heat.
• Payback = Cost of insulation/Savings per year
• Non-Renewable Energy:

  • Coal
  • Oil
  • Gas
  • Nuclear
• Renewable Energy:

  • Solar
  • Wind
  • Tidal
  • Geothermal
  • Hydro-electric
  • Biomass
• Powerstations burn fuel to boil water into steam. The steam turns the turbine which spins the generator. The generator produce electricity which goes out to the national grid.
• Advantages of non-renewable energy:

  • Low fuel cost
  • Dependable
  • Low start up time
• Disadvantages of non-renewable energy:

  • High commissions (nuclear)
  • Depleting supply
  • Pollution
• Advantages of renewable energy:

  • Won't run out
  • Doesn't emit greenhouse gases
  • Can be used to meet demand surges (hydro-electric)
  • Low cost
• Disadvantages of renewable energy:

  • Unreliable
  • Expensive
  • Can destroy habitats
• The national grid - A network of powerstations, transformers and wires that bring electricity to our homes.
• Step Up Transformers - Increases the voltage to reduce energy loss.
• Step Down Transformers - Decrease the voltage to ensure the electricity is safe to use in our homes.
• $P =$$IV$
• Efficiency = Useful energy/ Total energy × 100