Energy

• Energy can neither be created nor destroyed - only converted from one store form of energy to another
• Energy stores:

  • Thermal
  • Kinetic
  • Gravitational potential
  • Elastic potential
  • Chemical
  • Magnetic
  • Electrostatic
  • Nuclear
• How is energy transferred?

  • mechanically - doing work
  • Electrically - moving charges
  • Heating
  • Radiation - light/sound
• What is kinetic energy and what’s the equation for it?

  • Anything that is moving has energy in it’s kinetic energy store
  • Ek (j)= 0.5 x mass (kg) x speed^2 (m/s)
• What is gravitational potential and what is the equation for it?

  • Lifting an object into a gravitational field requires work - causes energy to transfer to the g.p.e store of the raised object
  • Ep (j) = mass x gravitational field strength (N/kg) x height (m)
• What is elastic potential and what is the equation for it?

  • Stretching or compressing an object can transfer energy to its E.P.E store
  • Ee (j) x 0.5 x spring constant (N/m) x extension^2 (m)
• Thermal energy is contained within a system that is responsible for its temperature
• Energy can be transferred usefully, stored or dissipated but can never be destroyed or created
• When energy is transferred not all energy is 100% transferred to the product usefully - some energy is always dissipated
• Dissipated energy is sometimes known as wasted energy
• Power is the rate of doing work - how much per second
• Power is the rate of energy transfer or the rate of doing work
• Power is measured in Watts - 1 watt = 1 joule of energy transferred per second
• Power equations :

  Power = Energy transferred/time

  Power = Work down/time
• A powerful machine is one which transfers a lot of energy in a short amount of time