Energy

• What happens to energy when it is transferred between different energy stores?

  Energy is never used up; it is transferred between different energy stores and objects.
• What occurs when energy is transferred to an object?

  The energy is stored in one of the object's energy stores.
• What are the main types of energy stores you need to know?

  1. Thermal energy stores
  2. Kinetic energy stores
  3. Gravitational potential energy stores
  4. Elastic potential energy
• How does movement relate to an object's kinetic energy store?

  Anything that is moving has energy in its kinetic energy store.
• What factors affect the energy in an object's kinetic energy store?

  The energy depends on the object's mass and speed.
• What is the formula for calculating kinetic energy?

  Kinetic energy (E_k) = $\frac{1}{2}mv^2$
• Calculate the kinetic energy of a car with a mass of 2500 kg traveling at 20 m/s.

  The kinetic energy is 500,000 J.
• What does specific heat capacity refer to?

  It refers to how hard it is to heat something up.
• How much energy is needed to warm 1 kg of water by 1°C?

  4200 J is needed to warm 1 kg of water by 1°C.
• What happens to materials with high specific heat capacities when they cool down?

  They release a lot of energy when they cool down.
• What is the equation that links change in thermal energy, mass, specific heat capacity, and temperature change?

  ΔE = mcΔθ
• What are the steps to investigate specific heat capacities of materials?

  1. Measure the mass of the block.
  2. Insert the heater and thermometer.
  3. Wrap the block with insulating material.
  4. Measure initial temperatures and set power supply.
  5. Turn on power and start stopwatch.
  6. Record temperature and current readings.
  7. Calculate power and energy transformed.
  8. Plot graph of energy transferred vs. temperature increase.
  9. Find the gradient for specific heat capacity.
• How do you calculate the final temperature of water after energy transfer?

  Use the energy equation with specific heat capacity.
• What does the conservation of energy principle state?

  Energy can be transferred, stored, or dissipated but can never be created or destroyed.
• What happens to energy during a transfer?

  Not all energy is usually transferred into the desired store; some is dissipated.
• What is dissipated energy often referred to as?

  Dissipated energy is sometimes called 'wasted energy.'
• How does a mobile phone use energy?

  Energy is transferred from the chemical energy store of the battery.
• What occurs in a closed system when a cold spoon is placed in hot soup?

  The spoon's temperature increases while the soup's temperature decreases slightly.
• What is power defined as?

  Power is the rate of energy transfer or the rate of doing work.
• How is power measured?

  Power is measured in watts.
• What is the equation for calculating power based on energy transferred?

  Power (P) = E/t
• What is the equation for calculating power based on work done?

  Power (P) = W/t
• How does the power of two identical cars with different engine powers affect their race?

  The car with the more powerful engine will finish the race faster.
• What is conduction?

  Conduction is the process where vibrating particles transfer energy to neighboring particles.
• How does energy transfer occur in conduction?

  Energy is shared across the object being heated through particle collisions.
• What is thermal conductivity?

  Thermal conductivity is a measure of how quickly energy is transferred through a material.
• What is convection?

  Convection is where energetic particles move away from hotter to cooler regions.
• What are some methods to reduce unwanted energy transfers?

  • Lubrication reduces frictional forces.
  • Insulation reduces the rate of energy transfer by heating.
• How does lubrication help in energy transfer?

  Lubrication reduces friction between moving surfaces, minimizing energy dissipation.
• What are some examples of insulation methods to reduce heat loss?

  • Thick walls made from low thermal conductivity materials.
  • Use of thermal insulation materials.
• What is the relationship between energy transfers and efficiency?

  Most devices waste energy, and the less energy wasted, the more efficient the device is.
• How is efficiency calculated?

  Efficiency = Useful output energy transfer / Total input energy transfer.
• How can you calculate efficiency using power?

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

  The useful power output is 420 W.
• Why is no device 100% efficient?

  No device is 100% efficient because some energy is always wasted, usually as thermal energy.
• What are the main non-renewable energy resources?

  The main non-renewable energy resources are coal, oil, and natural gas.
• What is a characteristic of renewable energy resources?

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

  1. Solar
  2. Wind
  3. Water waves
  4. Hydro-electricity
  5. Bio-fuel
  6. Tides
  7. Geothermal
• How are non-renewable energy resources typically used?

  They are typically burned to provide energy.
• What fuels are used in petrol and diesel powered vehicles?

  Petrol and diesel are created from oil.