Science - Portable power (Topic 3)

• An electrochemical cell is a device that converts the energy from chemical reactions into electricity
• Many modern devices operate using Voltaic cells
• Voltaic cell: A device that spontaneously produces electricity by redox reactions
• Most people refer to Voltaic cells as batteries
• Battery: A set of Voltaic cells joined to produce an electric current
• Components of an Electrochemical Cell:
• Electrodes are made of metal elements
• Positive Electrode = CATHODE:

  • This electrode will GAIN electrons
• Negative Electrode = ANODE:

  • This electrode will LOSE electrons
• Electrolyte is a material that can conduct electricity
• Wet cells use a liquid electrolyte
• Dry cells have a plastic, paste, or ceramic solid electrolyte
• Electrons move from ANODE to CATHODE
• ANODE loses electrons and slowly disintegrates
• CATHODE gains electrons and slowly gains mass
• At the ANODE, the reaction converts the solid metal into an ion, releasing its electrons
• At the CATHODE, the reaction converts the ion into solid metal
• A battery “runs out” when its ANODE is consumed and can no longer donate electrons
• Electrodes are different metals that react with different strengths, resulting in higher voltage
• Concentration of Electrolyte:

  • Higher concentration increases the rate of reactions at the electrodes
• Surface area of Electrodes:

  • Greater surface area exposed to the electrolyte means more of a reaction taking place
• Electrolytic cells are chemical systems where non-spontaneous oxidation and reduction reactions occur due to the application of electrical energy
• Gold and Silver are resistant to corrosion because they are not easily oxidized
• To protect objects from corrosion, a thin layer of corrosion-resistant metal is applied to the surface using a process called electroplating, which is a variation of Voltaic cells
• Electroplating is the process of depositing a metal at the cathode of an electrolytic cell
• During electroplating, the object to be coated is immersed in a solution containing metal ions that will form the corrosion-resistant surface
• An external power source is used to force electrons to flow through the two electrodes: one electrode connects to the object to be coated, and the other to a second electrode in the solution to complete the circuit
• Electrochemical cell

  
• Manipulated Variable - Variable changed by the person doing to experiment
• Responding Variable - The result of the effect of the Manipulated Variable
• Controlled Variable - Variables that stays the same
• Independent Variable - Changed by the researcher
• Dependant Variable - Changes as a response to the Independent variable
• Transformer function:

  • Step up voltage for transport over long distances
  • Step down voltage for use in homes and factories
• Power meter in homes:

  • Connects home to power grid through a step-down transformer and a power meter
  • Records total electric energy supplied to devices in the house
  • Energy then travels to a service panel where wires connect to the main circuit breaker
  • Main breaker acts as a switch and safety device to cut off power to the house
• Transformer function:

  • Step up voltage for transport over long distances
  • Step down voltage for use in homes and factories
• Electric cables in branch circuits contain three wires:

  • Live wire: Carries electricity from generating station
  • Neutral wire: Provides return path for electricity
  • Ground wire: Provides path to ground in case of malfunction
• Electric power is the amount of electric energy converted into other forms of energy (heat, light, sound, or motion) per second
• Unit for power is joules per second, also known as watt (W)

  • 1 kW = 1000W
• Incandescent light bulbs:

  • Used in most homes
  • Only about 5% efficient, with 95% of input energy wasted as heat