Lesson 21.3

• Energy Transformations


  How energy is transferred
• Energy transfer in plants

  1. Sun transfers light energy to plants

  2. Plants use light energy through photosynthesis to convert to chemical energy

  3. Chemical energy is converted to fuel processes within plants
• Energy transfer in everyday life - appliances

  1. Appliances receive electrical energy

  2. Electrical energy is converted to heat, light, sound
• Energy transfer in everyday life - ball

  1. Ball has gravitational potential energy when held

  2. When dropped, gravitational potential energy is converted to kinetic energy
• Energy transfer in archery

  1. Bow stores elastic potential energy when drawn

  2. Elastic potential energy is transferred to arrow as kinetic energy when released
• Hooke's law


  Describes the mechanism of a spring: F = -kx, where F is force, k is spring stiffness, and x is spring contraction
• Energy transfer in roller coasters

  1. Cars change between kinetic and potential energy as they move through the track

  2. Loops are designed to be less than half the height of the highest point for safety

  3. Engineers try to minimize friction by lubricating parts and reducing rust
• Energy transformation in steam locomotives

  1. Burned coal heats water in boiler

  2. Expanding water moves pistons connected to drive train

  3. Allows train to move forward
• Energy transformation in power plants

  1. Heat from burning fossil fuels boils water

  2. Expanding water moves pistons/turbines

  3. Generators produce electricity
• In all energy transformations, there is energy loss in the form of heat
• Energy cannot be created nor destroyed, but can be transformed from one form to another
• In all energy transformations, there is always energy loss in the form of heat
• The total energy of a system remains the same
• Energy cannot be created nor destroyed
• Light energy received by plants is transformed into chemical energy, not mechanical energy
• Heat is always produced in energy transformations
• The amount of energy stored in a battery is not equal to the energy produced when a bulb lights up
• Hydroelectric power plants use the energy of water, not hydrogen, to create electricity
• The energy of the Earth right now is equal to the energy the Earth has ever since the beginning, as energy cannot be created or destroyed