electricity

• electrical energy - the energy of charged particles
• what uses electrical energy?

  • human body - moving eyes to read relies on electrical signals in muscles; electrical signals help maintain breathing and heartbeat
  • technology - touch-sensitive screens, robots, maglev trains
• energy is neither created or destroyed but is transformed
• mechanical energy - the sum of kinetic energy and potential energy
• kinetic energy - the energy of motion
• potential energy - stored energy that a system has due to its position or condition
• potential energy example

  • water at the top of a waterfall, just before it falls, has potential energy because of its position + has kinetic energy because it is moving
• chemical energy - energy stored in chemical bonds, and released when a chemical reaction occurs
• chemical energy examples

  • batteries store chemical energy
  • chemical energy stored in animals and plants is called biomass
  • fossil fuels (coal, oil, natural gas) store chemical energy
• solar energy - energy carried by electromagnetic radiation given off by the sun
• fossil fuels and biomass result from energy from the sun being captured by plants and plant-like organisms
• nuclear energy - energy generated by forming new atoms
• nuclear fusion - new atoms are made as smaller atoms collide and fuse (occur in the sun and stars)
• nuclear fission - new atoms are made by splitting larger atoms (carried out in reactors on earth); most of the energy is thermal energy, which is used to boil water into steam; pressure from the moving steam turns turbines connected to generators
• thermal energy - energy due to the rapid motion of particles that make up an object; detected as heat
• thermal energy examples

  • sources include nuclear reactions or from Earth's interior (geothermal energy) where steam and hot water form naturally
  • geysers, volcanoes, hot springs
• most of the electrical energy in canada is generated by transforming kinetic energy into electrical energy; source of kinetic energy may be moving water, wind, or moving steam produced by nuclear reactions or burning fossil fuels
• generator system - a system that transforms kinetic energy to electrical energy
• turbine - steam, water, or wind cause the turbine to spin
• shaft - as the turbine spins, the shaft spins
• generator - kinetic energy of the spinning shaft is transformed into electrical energy inside the generator
• British Columbia uses river flow and fossil fuels

  • river flow is the main source (hydroelectric energy); water flowing freely in a river turns a turbine
  • thermal energy from burning coal is used to boil water into steam
  • no nuclear reactors
• wind

  • kinetic energy of wind is transformed into electrical energy as the moving air turns the turbine of a generator system; have anemometers
• sunlight

  • photovoltaic cells transform the energy of visible light to electrical energy
  • when visible light strikes electrons in the photovoltaic cells, the electrons absorb enough energy to flow freely and generate electrical energy
• geothermal sources

  • where earth's crust is thin and molten rock comes close to the surface, hot steam can be used to turn turbines to generate electrical energy
• waves and tides

  • tides and the rise and fall of waves can turn turbines to generate electrical energy
• static charge - static electricity; electric charge that stays in one place until it is discharged (lost) to other objects or to the air; measured in coulombs; takes the addition or removal of 6.25x10^18 electrons to produce 1C of charge
• coulomb - unit of electric charge
• in solid materials, the positive nucleus stay in the centre of the atom, but the electrons can be rubbed off the material; all solid materials are charged by the transfer of electrons
• friction - occurs when objects rub against each other; results in one object losing electrons while the other object gains them; electrons will either stay on the surface of the new material or travel through it
• insulators - materials that do not allow electrons to move easily; can retain a static charge
• insulator examples

  • glass
  • plastics
  • ceramics
  • dry wood
• conductors - materials that allow electrons to move easily; will allow a charge to flow
• conductor examples

  • metals
• conductivity - an indication of how easily charges travel through a material; electrons can move through almost all metals and move through some metals more easily; the higher the conductivity of a material, the mor easily electrons can move through
• van de graaff generator - a device that uses friction to produce a large static charge on a metal dome; a moving belt produces a static charge at the base of the generator; the belt carries the charge to the metal dome, where it is collected
• grounding - connecting a conductor so that electric charge flows into earth's surface; removes an object's charge to the ground
• a force is a push or pull

  • contact forces - forces that can have an effect only on objects when they touch
  • action-at-a-distance - forces that can have an effect on an object without touching it
• electric force - push or pull between charged objects; an example of an action-at-a-distance force
• laws of static charge

  1. like charges repel
  2. opposite charges attract
  3. neutral objects are attracted to charged objects