Chapter 12/13

• Efficiency formula


  eff: eou/ein x100
• The higher the percentage the more efficient
• Energuide Labels


  Consider the cost of device & cost of operating
• The label provides estimations on the amount of electrical energy the device uses in a year
• Electric Current


  The rate of election flow in a circuit
• Electrical Quantity


  • Current
  • Potential Difference (Voltage)
  • Resistance
• Current is measured in

  Ampere (A)
• Measuring Current


  1. Ammeter is used

  2. Must be connected in series with the load to measure
• Potential Difference (Voltage)


  The amount of energy needed to move electric charge from one point to another
• Voltage is measured in


  Volts (V)
• Measuring Potential Difference


  1. Voltmeter is used

  2. Must be connected in parallel to what's being measured
• Electrical Resistance


  The ability of a material to oppose\resist the flow of elections
• Resistance


  Ohm (Ω)
• Measuring Resistance


  1. Ohmeter is used

  2. Must be connected in parallel
• Resistors


  • A device that reduces current in a circuit
  • The lower the current the higher the resistance
• Factors that affect resistance

  • Material (conductor vs insulator)
  • Cross sectional area (thick vs thin wire)
  • Length (long vs short)
  • Temperature (warm vs cold)
• Current in series


  The current is the same at all points
• Voltage in series


  Voltage is divided equally among the loads
• Resistance in series


  Resistance increases as loads are added
• Current in parallel


  Currents add up to the total at the battery
• Voltage in parallel


  Each load uses the voltage that's supplied
• Resistance in parallel


  Resistance decreases as loads are added
• Significant figures rules


  • All non-zero digits are significant
  • Zeros between numbers are significant
  • Trailing zeros with a decimal point are significant
  • Zeros at the beginning to place a decimal are not significant
• Calculations with significant figures

  1. Determine the number with the least significant figures

  2. Round the answer to the least number of significant figures
• Renewable energy


  • Self-replenishing
  • Less destructive to the environment
• Disadvantages of renewable energy

  • Not always available
  • Needs a lot of space
  • Not always consistent
• Non-renewable energy


  • Uses less space
  • Is reliable energy
• Disadvantages of non-renewable energy

  • Pollutes the environment
  • Unsustainable
  • Releases toxic chemicals
• Sources of electrical energy

  • Batteries
  • Electric generating stations
• Primary cell

  Can only be used once
• Secondary cell


  Can be reused once recharged
• Direct Current (DC)


  All the electrons move in one direction through the circuit
• Alternating Current (AC)


  Electrons move back and forth, alternating their direction
• Electrical Power


  The rate at which electrical energy is produced or consumed during a specific time
• Kilowatt-Hour (kWh)


  Measure of electrical energy usage
• Efficiency


  A measure of how much useful energy is produced, compared to how much energy was supplied
• Electrons


  Move through the material
• Electrical energy is converted into thermal energy
• Factors that affect resistance


  • Type of material
  • Cross sectional area
  • Length
  • Temperature
• Type of material


  Some materials are better conductors than others and offer less resistance to the flow of charge