Electricity and electromagnetism 1.2 & 1.9

• Forms of energy

  • Thermal
  • Kinetic
  • Chemical
  • Electrical
  • Gravitational
  • Elastic
  • Nuclear
  • Sound
  • Light
• Conservation of energy

  • Energy can never be created or destroyed
  • Energy can be transferred from one type to another
• electrical energy is considered to be the most useful type of energy because it can be transferred into other types of energy easily
• Renewable energy resources

  • wind
  • solar
  • tidal
  • waves
  • hydroelectric
  • pumped storage
  • geothermal
• Non renewable energy resources

  • coal
  • oil
  • natural gas
  • nuclear
• Components of thermal power station

  furnace --> boiler --> turbine --> generator
• sustainability

  will the energy sources be available for future generations
• start up time

  how quickly can a power station using this resource be brought on line
• generating capacity

  can the resource be used to generate relatively large amount of electricity
• reliability

  can the resources be used to generate electricity when it is needed to meet expected demand
• environmental impact

  does using the resource impact negatively on the environment
• economic

  does the resource provide value for money in terms of installation costs compared with the quantity
• why we use non renewable energy?

  • economic
  • generating capacity
  • reliable
• nuclear power stations produce radioactive waste which is ionising
• combustion of fossil fuels releases carbon dioxide which causes global warming; and they release sulphur dioxide which causes acid rain
• National Grid

  Provides electricity to consumers reliably using transformers and overhead cables
• coal and nuclear power stations are used to supply the baseload because they have long start up times
• when electricity demands are high short start up time power stations are turned on e.g. hydroelectric
• peak demand for electricity is when its used the most in a day
• surplus is when there is more power than needed
• when there is surplus in the night, the national grid uses that power to do pumped storage so there's water in the upper reservoir
• step up transformers increase the voltage which decreases the current, wasting less energy as heat making it more efficient
• step down transformers decrease the voltage to a safe level for consumers
• power = voltage x current
• power = resistance x current$^2$
• the area around a magnet where it exerts a force is called a magnetic field
• we can show magnetic field lines by using plotting compasses or iron fillings
• rules for magnetic field lines

  1. closer the lines are, the stronger the field
  2. arrows go from north to south
• when an electric current flows through a conductor it produces a magnetic field around the conductor. current direction is found by using the right hand grip rule
• we can make the magnetic field stronger by increasing the current or increasing the length of wire
• a solenoid is an electromagnet
• electromagnets can be made stronger by...

  • increasing current
  • increasing length of coil of wire
  • adding an iron core
• electromagnets are better than permanent magnets because

  • they can be turned on and off
  • you can change the strength
• the motor effect uses flemmings left hand rule while the electromagnetic induction uses flemmings right hand rule
• transformers have an AC input sent to the primary coil
• in transformers the changing ac input current creates a changing magnetic field
• in transformers, the iron core transfers the magnetic field to the secondary coil
• more coils in transformer induces a bigger voltage
• voltage may not be the same as input voltage because some energy is lost as heat
• transformer rule

  voltage across primary coil / voltage across secondary coil = number of turns of coil on primary / number of turns of coil on secondary