Science | Exam | Electricity

• Current Electricity

  Electric charge that moves from a source of electrical energy, through a controlled path through an electric current. Electrons flow in a controlled way through a conductor.
• Electrical Circuits


  A continuous path in which electrons can flow.
• Parts required for a simple circuit

  • Energy source
  • Conducting wires
  • Load
  • Switch
• Electric Cells


  Converts chemical energy into electrical energy. Made up of two electrodes (conductive metals) in a conducting solution. Ex. Batteries are made of electric cells linked together.
• Fuel Cells


  An electric cell that combines hydrogen and oxygen to produce electrical energy. Requires a continuous supply of fuel and produces a waste product.
• Power-Generating Stations


  Converts mechanical energy into electrical energy. The turbine is connected to a generator, electrons within a wire in the generator begin to flow. They move into the electrical outlets of our home.
• Photovoltaic Cells


  A device that converts light directly into electrical energy. Light shining on the cell allows electrons to flow. Ex. a solar cell captures energy.
• Renewable


  Natural energy resource that is unlimited or can be replenished by natural processes in a short period of time.
• Non-Renewable


  A resource that cannot be replaced as quickly as it is consumed.
• Different types of generating stations

  • Hydro
  • Tidal
  • Wind
  • Fossil Fuels
  • Nuclear
  • Biomass
  • Geothermal
• Alternating Current


  Current where the flow of electrons moves back and forth, produced by generating stations.
• Direct Current


  Current where electrons flow in one direction, produced by an electric cell (battery).
• Series Circuits


  • One path for electrons to flow, current is the same, voltage is additive
• Parallel Circuits


  • Two or more paths for electrons to flow, current is additive, voltage is the same
• Unscrewing a light bulb in a series circuit

  Flow of electrons stops (bulbs don't work)
• Unscrewing a light bulb in a parallel circuit

  Electrons are still flowing (they have their own paths)
• Adding a light bulb in a series circuit

  Bulbs become dim when bulbs are added
• Adding a light bulb in a parallel circuit

  All bulbs remain with the same amount of light
• Electrical Quantities


  • Charge (Q, coulomb/C)
  • Current (I, amperes/A)
  • Voltage (V, volts/V)
  • Energy (E, joules/J)
  • Resistance (R, ohms/Ω)
  • Power (P, watts/W)
• Factors affecting resistance of a wire

  • Length: longer wire, more resistance
  • Width: thinner wire, more resistance
  • Temperature: hotter wire, more resistance
  • Material: lower conductivity, more resistance
• More resistance there is

  Electrons move slower, takes longer for electrons to pass through
• Ammeter


  Measures the current at any point in a circuit. Current flows through the ammeter and it must be connected inside the circuit.
• Voltmeter


  Measures the potential differences across two points. It must be connected outside of the circuit across from the battery or the load.
• Ways to reduce use of electricity

  • Unplug unused electrical devices
  • Play recreational sports instead of online games
  • Turn off heating/ac when not used
  • Shut off water when not using
• Electrical Efficiency


  Device that uses less electrical energy. % of efficiency = electrons out/electrons in x 100
• Fuse


  Some very old buildings have fuse boxes. A fuse has a small wire that will melt and break apart when the current gets too high. When a fuse "blows out" it must be replaced with a new fuse.
• Circuit Breaker


  Prevents any circuit from carrying too much current and starting a fire. Made of two metals, when the metals get too hot, they bend causing the switch to open.