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Topic 5 - Portable Power

Topic 5 - Portable Power. Electrolyte: Wet or dry substance that conducts electricity because it can form ions. Eg . Salt water, battery acid An electrochemical cell or cell is a single unit that can produce an electric current. There are two parts:

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Topic 5 - Portable Power

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  1. Topic 5 - Portable Power • Electrolyte: Wet or dry substance that conducts electricity because it can form ions. Eg. Salt water, battery acid • An electrochemical cell or cell is a single unit that can produce an electric current. • There are two parts: • Electrodes: Must be made of two different metals

  2. A chemical reaction takes place between the electrolyte and the electrodes causing the electrons to accumulate at the negative end and the protons to gather at the positive end. • If hooked in a circuit, the electrons travel from the negative end to the positive end.

  3. Wet cells use a liquid electrolyte. • Dry cells –the electricity-producing cells, referred to as 'batteries', are called dry cells, because the chemicals used in them are a paste. • Several cells connected in series produces a higher voltage, and is commonly referred to as a battery, which is a sealed case with only two terminals. (Page 301)

  4. A primary cell is one in which the reactions will not continue after the reactants are used up. • A secondary cell uses chemical reactions, which can be reversed. These are referred to as rechargeable batteries.

  5. Types of ‘dry’ cells • zinc-carbon • Uses: Flashlights, portable stereos, CD players, walkmans • Pros and Cons: Not efficient at low temperatures

  6. alkaline • Uses: Flashlights, portable stereos, CD players, walkmans • Pros and Cons: Last longer than zinc carbon, but more expensive

  7. zinc-air • Uses: Calculators, hearing aids, watches • Pros and Cons: Highest energy per unit mass, but discharge rapidly

  8. Secondary Dry Cells nickel-cadmium • Uses: Electric shavers, laptops, powertools, portable TV’s • Pros and Cons: Rechargeable hundreds of times

  9. nickel-metal hydride • Uses: Cameras, laptops, cell phones, hand tools, toys • Pros and Cons: Less toxic than NiCad – 40% more energy density than NiCad, rechargeable, no memory effect, lose charge when stored

  10. Secondary Wet Cells lead acid • Uses: Cars, motorbikes, snowmobiles, golf carts • Pros and Cons: Dependable, but heavy and has a corrosive liquid

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