Energy transfers

• What is energy defined as?

  Ability of a body to do work
• What is the unit of energy?

  Newton's meter or Joule
• Why is energy considered a scalar quantity?

  It has only magnitude, no direction
• What is kinetic energy?

  Energy possessed by a mass due to movement
• What is the formula for kinetic energy?

  $K =$$\frac{1}{2} m v^2$
• What does 'm' represent in the kinetic energy formula?

  Mass in kilograms
• What does 'v' represent in the kinetic energy formula?

  Speed in meters per second
• What is gravitational potential energy?

  Energy stored due to position in a gravitational field
• What is the formula for gravitational potential energy?

  $GP =$$m g h$
• What does 'g' represent in the gravitational potential energy formula?

  Acceleration due to gravity, 10 m/s²
• What does 'h' represent in the gravitational potential energy formula?

  Change in height in meters
• What is mechanical energy?

  Sum of kinetic and potential energy
• What is elastic potential energy?

  Energy stored due to changes in shape
• What is chemical potential energy?

  Energy stored within chemical bonds
• What is electrical potential energy?

  Energy stored in charges under an electrical field
• What is nuclear energy?

  Energy stored in the nucleus
• What is thermal energy?

  Energy responsible for a system's temperature
• What is light energy?

  Radiant energy, electromagnetic radiation
• What is sound energy?

  Energy transferred through particle vibrations
• What does the principle of conservation of energy state?

  Energy cannot be created or destroyed
• How is efficiency defined?

  Ratio of useful energy output to total input
• What is the efficiency of a light bulb with 120 J input and 50 J output?

  0.417 or 41.7%
• What is the efficiency of a television with 550 J input and 470 J output?

  0.855 or 85.5%
• What is the efficiency of an electric motor with 750 J input and 450 J output?

  0.6 or 60%
• What is the efficiency of a running person with 800 J input and 500 J output?

  0.625 or 62.5%
• What are Sankey diagrams used for?

  • Represent energy transfers
  • Show proportions of energy transfers
  • Indicate useful and wasted energy
• What does the width of arrows in a Sankey diagram represent?

  Amount of energy being transferred
• What does the left-hand side of a Sankey diagram represent?

  Energy transferred into the system
• What does the straight arrow in a Sankey diagram represent?

  Useful energy output
• What does the bent arrow in a Sankey diagram represent?

  Wasted energy output
• In a Sankey diagram, if L1 equals L2 + L3 + L4, what does L1 represent?

  Total energy input
• How do you calculate the efficiency of an electric motor with 1,000 J input and 600 J output?

  0.6 or 60%
• What is thermal energy transfer?

  Transfer from hot to cold objects
• What is thermal equilibrium?

  Equal temperature between two objects
• What are the three methods of thermal energy transfer?

  Conduction, convection, and radiation
• What is conduction?

  Transfer of heat mainly in solids
• How does conduction occur in solids?

  Atoms collide and transfer kinetic energy
• Why do metals conduct heat better than non-metals?

  Metals have free-moving electrons
• What are good conductors of heat?

  Substances that transfer heat easily
• Name some good conductors of heat.

  Silver, copper, iron, aluminum