Cond&convec, energy transfer, efficiency, energy sources etc

• What are the two main processes of energy transfer by heating discussed in the material?

  Conduction and convection
• What is conduction?

  Conduction is the process where vibrating particles transfer energy to neighboring particles.
• How is energy transferred to an object by heating?

  It is transferred to the thermal store of the object.
• What happens to the energy in an object when it is heated?

  The energy is shared across the kinetic energy stores of the particles in the object.
• What occurs during the collisions of particles in a heated object?

  Energy is transferred between the particles' kinetic energy stores.
• What is thermal conductivity?

  Thermal conductivity is a measure of how quickly energy is transferred through a material.
• In which states of matter does convection occur?

  Convection occurs only in liquids and gases.
• What happens to the density of a gas when it is heated?

  The density of the gas decreases as the particles move faster and the space between them increases.
• What is a convection current?

  A convection current is created when warmer, less dense regions of a fluid rise and are replaced by cooler, denser regions.
• How do radiators create convection currents in a room?

  • Energy is transferred from the radiator to nearby air particles by conduction.
  • The air by the radiator becomes warmer and less dense.
  • Warm air rises and is replaced by cooler air, creating a cycle.
• What are two methods to reduce unwanted energy transfers?

  Lubrication and thermal insulation
• How does lubrication reduce energy loss?

  Lubrication reduces frictional forces between moving objects.
• What is the effect of thick walls made from low thermal conductivity materials on energy transfer?

  They slow the rate of energy transfer, helping the building to cool more slowly.
• What are some examples of thermal insulation methods?

  • Cavity walls with air gaps
  • Loft insulation
  • Double-glazed windows
  • Draught excluders
• What is the purpose of the experiment to investigate the effectiveness of thermal insulators?

  To determine which materials reduce energy transfer the most.
• What is the equation for efficiency?

  Efficiency = Useful output energy transfer / Total input energy transfer
• If a blender has a total input power of 600 W and is 70% efficient, what is the useful output power?

  420 W
• Why is no device 100% efficient?

  Because some energy is usually wasted to useless thermal energy stores.
• What are the three main fossil fuels?

  Coal, oil, and natural gas
• What is a characteristic of renewable energy resources?

  They will never run out as they can be renewed as they are used.
• What are some examples of renewable energy resources?

  • Solar
  • Wind
  • Hydro-electricity
  • Bio-fuel
  • Tides
  • Geothermal
• How is natural gas used for heating in homes?

  Natural gas is used to heat water, which is then pumped into radiators.
• What is the main disadvantage of wind power?

  Wind power can be unreliable due to varying wind conditions.
• What is a drawback of solar cells?

  They can only generate electricity during the daytime.
• What are the advantages and disadvantages of wind power?

  Advantages:

  • No pollution during operation
  • Low running costs

  
  

  Disadvantages:

  • Spoils the view
  • Noisy
  • Unreliable due to wind conditions
• What are the advantages and disadvantages of solar power?

  Advantages:

  • No pollution
  • Free energy after initial costs

  
  

  Disadvantages:

  • High initial costs
  • Limited to daytime use
• What is geothermal power used for?

  Geothermal power is used to heat buildings and generate electricity.
• What do solar cells generate directly from sunlight?

  Electric currents
• Why are solar cells often used in calculators and watches?

  Because they don’t use much electricity
• Where is solar power often used?

  In remote places with limited energy options
• What is a drawback of solar power manufacturing?

  It uses a lot of energy to manufacture
• When is solar power a reliable source of energy?

  During the daytime in sunny countries
• What is a limitation of solar power regarding demand?

  You can’t increase power output during extra demand
• What are the initial costs associated with solar cells?

  They are high, but energy becomes free afterward
• On what scale are solar cells usually used to generate electricity?

  Relatively small scale
• Where can geothermal power be harnessed?

  In volcanic areas or where hot rocks are near the surface
• What is the main source of energy for geothermal power?

  The slow decay of radioactive elements deep inside the Earth
• What are the environmental impacts of geothermal power?

  It does very little damage to the environment
• How can geothermal power be utilized?

  To generate electricity or heat buildings directly
• What are the main drawbacks of geothermal power?

  Limited suitable locations and high construction costs