p1 conservation and dissipation of energy

• Energy cannot be created or destroyed only transformed from one form to another
• Some energy is transformed in a non-useful way reducing the efficiency
• Work done means the same as energy transferred
• Work done to overcome friction is mainly transferred into energy by heating
• the kinetic energy of a moving object is transeferred to thermal energy reducing efficiency
• On earth we always have the force of gravity acting on us
• When we are above the earths surface area we have gravitational potential (stored) energy
• The gravitational potential energy depends on the mass of an object the height and the gravitational field strength
• All moving objects have kinetic energy
• kenetic energy depends on the mass and speed of an object
• The energy an object has when it has been stretched or squashed is elastic potential energy
• Work done = force x distance
• The spring constant is how easy the spring is to stretch
• The efficiency of a device measures how well it does the job it was designed to do
• Energy that is transferred in an non-useful way is wasted
• Wasted energy is usually in the form of heat(thermal energy) or sound
• Wasted energy is dissipated to the surroundings and heats up the atmosphere
• Sankey diagrams can be used to show efficiency
• The national grid

  power station

  step up transformer

  power lines

  step down transformer

  your home
• Electricity is a useful form of energy because it can be converted into many other forms of energy
• The power of an appliance is how much energy it uses every second
• Power is measured in watts or kilowatts
• Whilst things aren’t being used they have standby lights
• Energy that gets dissipated to the surroundings is hard to use again
• Power is how quickly the electrical energy is transferred into other forms of energy
• 1 watt = 1 joule per second
• If something has a high power, then it will transfer more energy from one form to another at a faster rate