Energy + Electricity Flashcards

• A system is an object or group of objects
• an object projected upwards initially has kinetic energy as it moves

  this kinetic energy is transferred into gravitational potential energy
• a moving object hitting and obstacle has kinetic energy which is making the object move

  there is a thermal energy store between the object and obstacle which makes the particles vibrate more
• an object accelerated by a constant force has work done by the force on the object

  the work done is converted into kinetic energy
• as a vehicle slows down, force is applied on the brakes

  work is done as there is friction between the brakes and the wheel

  kinetic energy decreses as it slows down

  friction increases the thermal energy in the brakes
• as water boils in an electrical kettle, electrical energy from the wires turns into thermal energy and heats up the water
• specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1 °C
• power is the rate at which energy is transferred or is the rate at which work is done
• a car with a more powerful engine will finish a race faster, as it transfers the same amount of energy but in a short space of time
• energy cant be created or destroyed

  it can only be transferred, stored or dissipated
• a cold spoon dropped in an insulated flask of hot soup is a example of energy transfer in a closed system

  as energy is transferred from the thermal energy of the soup to the useless thermal energy of the spoon

  energy transferred have occured but no energy has left the system
• an example of energy transfer being dissipated is using a mobile phone

  because energy is transferred from the chemical energy store of the battery

  some energy is dissipated to thermal energy store and the phone can become hot
• dissipated energy is sometimes called wasted energy because energy is being stored in a useless way
• you can reduce unwanted energy transfers through lubrication and thermal insulation
• lubrication can reduce friction between object surfaces when they move

  so liquids like oil, can flow easily between objects
• thermal insulation is installed in homes to reduce the transfer of thermal energy from the inside to the outside of the building
• cavity walls are made up of walls with air gaps in the middle

  this reduces the amount of energy conducted through the walls
• cavity wall insulation is the air gap in between cavity walls which is filled with foam

  this reduces energy transfer by convection
• loft insulation is put into the roof to stop energy transfer by convection
• double glazed windows have air gaps between two sheets of glass

  this prevents energy transfer by conduction
• draught excluders prevent cold draughts coming in through doors and windows
• conduction is when energy is being transferred between kinetic energy stores
• convection is when energetic particles move away from hotter to cooler regions
• thermal conductivity is the measure of how well a material conducts energy when it is heated
• a good thermal conductor will allow heat to pass easily through it, while a poor one won't
• the higher the thermal conductivity, the higher the rate of energy transfer
• we can improve efficiency by insulation, lubrication and making objects more streamlined
• our main energy resources are:

  fossil fuels

  nuclear fuel

  bio fuel

  wind

  hydro electricity

  geothermal

  tides

  the Sun

  water waves
• renewable energy will never run out and can we renewed at it is being used
• energy resources are used for transport, heating and to generate electricity
• wind power uses wind turbines with generators inside

  the rotating blades turn the generators and produces electricity
• advantages of wind power is that it doesn't cause pollution, no fuel costs and is renewable
• disadvantages of wind power is that it can ruin scenery, it can be very noisy and it relies on the weather
• hydropower uses water turning turbine blades which turns a generator producing electricity
• advantages of hydropower is that it doesn't produce greenhouse gases or air pollutants, it has low operating cost and it is reliable as long as there is enough rainfall
• the sun generates electricity directly from sunlight

  it is used to power electric road signs and satellites
• advantages of solar energy is that it doesn't produce greenhouse gases or air pollutants, it has low running costs and it is reliable if there is plenty of sunlight
• disadvantages of solar energy is that it only works when its sunny so isn't always reliable, it takes up space and it needs expensive equipment
• geothermal energy is energy from slow decay of radioactive elements
• geothermal is found in volcanic areas in underground thermal energy stores