Physics

• The principle of the conservation of energy is that energy cannot be created or destroyed, only transferred.
• The 4 types of energy stores include:

  • chemical energy
  • kinetic energy
  • gravitational potential energy
  • elastic potential energy
• Kinetic energy - all moving objects have kinetic energy.

  KE = ½mv²
• Gravitational potential energy - when an object moves higher off the ground

  GPE= mg🔺h
• 🔺= change
• Elastic Potential Energy - energy stored when an object is stretched or compressed.

  EPE= ½ke² 
• The different types of energy include:

  • sound
  • kinetic
  • thermal
  • light
  • electrical
  • magnetic
  • nuclear
• Useful energy is energy that is transferred for a useful purpose
• Work done is another way of saying energy transferred.

  Work done = force * distance
• efficiency = useful energy / total input energy
• wasted power = total power input - useful power
• efficiency can be improved by reducing friction
• weight = mass * gravity
• A system is an object or a group of objects
• Closed systems are where neither matter nor energy can enter or leave
• The 4 main ways of transferring energy include:

  • mechanically (an object moving due to a force acting on it)
  • electrically (current moving through a potential difference)
  • by heating (energy transferred from a hotter object to a colder object)
  • by radiation (energy transferred by light / sound waves )
• Dissipated energy is when energy is spread out and lost / transferred to the surroundings
• force = spring constant * extension
• gradient = spring constant
• gradient of a line = change in y co-ordinates / change in x co-ordinates
• Hooke's law explains that force and extension are directly proportional.
• Wasted energy is energy that is not usefully transferred
• Wasted energy is transferred to the surroundings
• Energy becomes less and less useful the more it spreads out
• Input energy is energy supplied to a device
• efficiency % = efficiency value * 100
• no device is 100% efficient
• Power is the rate of energy transfer, or the rate of doing work
• One watt is equivalent to 1 joule transferred per second
• power = energy / time
• Thermal Conductivity: the ability of a material to allow the flow of heat from its warmer surface through the material to its colder surface.
• Thermal flow is always from a higher temperature to a lower temperature. This is often called a 'temperature gradient'
• different ways of reducing the cost of energy at home include:

  • energy efficient boilers
  • installing solar panels
• ways of reducing energy loss in homes include:

  • loft insulation
  • wall insulation
  • double glazing
  • draft excluders
• change in thermal energy = mass * specific heat capacity * temprature change
• The specific heat capacity of a substance is the amount of energy needed to raise the temperature of a 1kg substance by 1 degree celcius
• The higher the thermal conductivity of a material, the faster the rate of heat transfer by conduction
• What energy source supplies most energy demands globally?

  Fossil fuels
• Biofuels are fuels taken from organisms that were recently living/ still living
• What does carbon neutral mean?

  the amount of carbon released by burning biofuels is balanced out by the amount of carbon dioxide living organisms take in