Transcript 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:
• Electrodes: Must be made of two different
metals
• 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.
• 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)
• 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.
Types of ‘dry’ cells
• zinc-carbon
• Uses: Flashlights, portable stereos, CD
players, walkmans
•
• Pros and Cons: Not efficient at low
temperatures
alkaline
• Uses: Flashlights, portable stereos, CD
players, walkmans
• Pros and Cons: Last longer than zinc carbon,
but more expensive
zinc-air
• Uses: Calculators, hearing aids, watches
• Pros and Cons: Highest energy per unit mass,
but discharge rapidly
•
Secondary Dry Cells
nickel-cadmium
• Uses: Electric shavers, laptops, powertools,
portable TV’s
• Pros and Cons: Rechargeable hundreds of
times
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
Secondary Wet Cells
lead acid
• Uses: Cars, motorbikes, snowmobiles, golf
carts
• Pros and Cons: Dependable, but heavy and
has a corrosive liquid