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Current Electricity
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Current Electricity

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  • *but instead of water flowing through the interior of a pipe, electricity is a flow of electrons across the surface of a metal (or other conductive material)
  • Like water, voltage (electrical force through potential difference) has the ability to do more work (or damage) with greater flow. (Wind causing a wave vs. earthquake causing a tsunami) If VOLTAGE is the FORCE pushing the water/electricity, CURRENT is how MUCH is flowing past per second
  • Lithium cobalt oxide and carbon (Li ion battery) manganese dioxide and zinc (Alkaline battery) lead dioxide and metallic lead (Car battery)
  • Zinc-carbon battery : The zinc-carbon chemistry is common in many inexpensive AAA, AA, C and D dry cell batteries. The anode is zinc , the cathode is manganese dioxide, and the electrolyte is ammonium chloride or zinc chloride. Alkaline battery : This chemistry is also common in AA, C and D dry cell batteries. The cathode is composed of a manganese dioxide mixture, while the anode is a zinc powder. It gets its name from the potassium hydroxide electrolyte, which is an alkaline substance. Lithium-ion battery (rechargeable) : Lithium chemistry is often used in high-performance devices, such as cell phones, digital cameras and even electric cars. A variety of substances are used in lithium batteries, but a common combination is a lithium cobalt oxide cathode and a carbon anode. Lead-acid battery (rechargeable) : This is the chemistry used in a typical car battery. The electrodes are usually made of lead dioxide and metallic lead, while the electrolyte is a sulfuric acid solution.
  • Transcript

    • 1. Current Electricity
    • 2. Electricity
      • Electricity is:
        • the movement of charged particles from one place to another.
    • 3. Static vs. Current
      • How is static electricity different than current electricity?
        • Static electricity involves a build-up of electric charge with a singular, momentary discharge.
        • Current electricity pertains to a continuous flow of electricity through a conductor.
      • Name two examples of each.
        • Static : lightning, static shock
        • Current : wall outlet, battery
    • 4. Current Electricity
      • A constant flow of charged particles through a conductive medium
      • Measured in Amperes (A)
        • 1 Amp = 6 billion billion electrons per second moving past a point
    • 5. Circuits
      • An electric circuit is a closed path of conductors through which current can flow
        • similar to water flowing through a pipe
    • 6. Current Flow
      • Electrons need some incentive to get started in order for electricity to flow.
        • A difference in electrical potential (build-up of charges) provides the force required for current to flow
      • Potential Difference: a measure of the difference in charges (electric PE) between two points
        • also called Electro-Motive Force (EMF) or Voltage
        • this force causes work to be done (current to flow)
        • measured in Volts
    • 7. Voltage
      • Voltage is the force created by a difference in electrical potential
        • similar to water pressure
      • Voltage examples:
        • AA battery: 1.5 V
        • 9 Volt battery: 9 V
        • Car battery: 12 V
        • Household outlet: 120 V
        • Electric chair: 1000 - 2450 V
    • 8. Batteries
      • Cells are individual compartments in a battery that produce energy
      • Chemical reactions take place which produce electricity
        • two electrodes (electron conductors)
          • each electrode is made of a different material
        • electrolyte liquid or paste
          • allows ions to flow between
    • 9. Inside Batteries
      • Electrodes:
        • one material donates electrons
          • negative electrode (anode)
          • connects to - terminal (outside)
        • other material accepts electrons
          • positive electrode (cathode)
          • connects to + terminal
      • Electrolyte:
        • paste in dry cell
          • i.e. alkaline (basic pH)
        • liquid in wet cell
          • i.e. sulfuric acid
      Dry Cell Wet Cell
    • 10. Resistance
      • Resistance is the tendency of a material to oppose current
        • measured in Ohms ( Ω )
        • conductive materials have lower resistance
        • increased resistance can produce heat & light
          • i.e. tungsten filaments in light bulbs
      • Resistors in electronics control the flow of electricity
    • 11. Resistance
      • Resistance affects voltage (force) and current (amount) of electricity flow
        • Resistance is affected by:
          • conductivity of the material
          • length of wire (longer wire = more resistance)
          • diameter of wire (wider wire = less resistance)
          • temperature
            • in metals
              • higher temps = more resistance
            • in carbon/silicon
              • higher temps = less resistance
    • 12. Ohm's Law
      • Voltage = Current x Resistance
        • (V) volts (I) amps (R) ohms
      • V = I • R
      • Current = Voltage  Resistance
      • I = V/R
      • Resistance = Voltage  Current
      • R = V/I
      Georg Simon Ohm (1787 - 1854)
    • 13. Ohm's Law
      • if I (current) = .005 amps
      • and V (voltage) = 10 volts
      • what is the resistance ( R )?
      • What formula should we use?
      • R = 10V/.005A
      • Resistance = 2,000 Ω
      R = V/I
    • 14. DC & AC
      • Direct Current (DC): electrons flow in one direction only
        • current flows from negative to positive
        • example: batteries
      • Alternating Current (AC): the direction of current changes rapidly over time
        • electrons change direction (move back and forth along a conductor) 60 times every second
        • positive & negative terminals constantly change
        • example: household wiring

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