Hello everyone,
Please excuse this really basic question, but I have been searching around for hours and can't seem to find a satisfactory explanation.
Fact: 1 volt is enough electrical potential to push 1 coulumb through
1 ohm of resistance in 1 sec.Why then is a AA battery rated at far less then 1 ampere?
Is there some resistance I'm not aware of?
Thanks everyone! I'm just getting started, as you can tell.
--foobarq
A battery has internal resistance. It also has a limited amount of charge. An AA battery has about 2900 mah capacity and while in theory, it could supply 1 A for about 2.9 hours, at this discharge rate it will not be able to do so. The rated capacity is based on a slower discharge rate-say 100ma (which is more typical of its use) where the battery is more efficient and the internal resistance stays low.
Why is a slower discharge rate more efficient?
Thanks.
Because with a higher load resistance (slower discharge rate) a smaller percentage of the total energy is lost in the internal resistance of the cell. If load resistance is equal to cell resistance each uses 50% of the energy, the cell's usage being wasted as heat. If the load resistance is 9 times the cell resistance the load gets 90% and the cell wastes 10%. It is actually a bit more complicated than that but that is the general idea.
Don Young
A good AA cell can deliver several amperes during short circuit. For the reasons described by others here, that is not how you want to operate with such a cell. One problem with carrying such a cell in a pocket full of paper clips is that when the cell does get circuited, all the chemical energy in the cell gets converted to heat. That can have some unhappy consequences.
BillE
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