You are ready to head on a fun family vacation when you realize that the car bat

Question

You are ready to head on a fun family vacation when you realize that the car battery is dead! Shoot! You do not have access to another 12 V car battery but you do have eight 1.5 V AA batteries available that you have gathered from electronics around the house. 1) Can you use these batteries to start your car and begin your trip? Why or why not? 2) Why are batteries differently sized even if they are the same voltage? (Ex. a 1.5 volt battery that can be used in a camera vs a goliath one-pound 1.5 volt battery that can be used in the laboratory)

Explanation / Answer

Won't work. The voltage of any real world battery drops a little or a lot, depending upon how much current it is asked to deliver. Large batteries can deliver more current before dropping too much. Your 12 volt car battery voltage drops to 9 or 10 volts when it is actually cranking the engine. Those AA batteries will drop to essentially nothing. One way to look at it is internal resistance: there is an implied resistor in series with any battery, and the smaller the battery the higher that resistance, dropping the voltage faster with increasing current. The other factor is simply battery drain. No battery has infinite capacity to pump out current .. they either go in the trash (AA cells) or get recharged (car battery). The AA's have so little capacity that even if they could somhow provide enough current to turn over the engine, they would run out almost instantly.

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