I'm running an Electricity merit badge session for my son's boy scout troop. One of the requirements is to make a simple electromagnet. For this, I was going to have the boys take a 12 foot length of 24 gauge wire and wrap it around a large nail and connect it to a AA alkaline cell.

The wire gauge chart tells me that 12 feet of wire is about 0.308 ohms. The nominal voltage of the AA is 1.5 volts, which would put the current at about 4.9 amps. However, when I actually connect it up, the measured voltage of the battery is actually dropping to about 0.9 volts, for a current of about 2.9 amps, which is within the amperage limits of 24 gauge wire.

My question is: Are there any safety concerns with connecting the AA cell this way? I realize that this will drain the energy out of the cell fairly quickly, but it doesn't need to last very long for this demo.

  • 1
    \$\begingroup\$ Pick a different wire. For example, a 15-foot length of AWG30 would be about 1.5 ohms, a much more reasonable load for the AA cell. \$\endgroup\$
    – Dave Tweed
    Aug 14, 2017 at 13:11
  • \$\begingroup\$ And/or more of it! 12 feet isn't a lot. \$\endgroup\$
    – user39382
    Aug 14, 2017 at 20:12

1 Answer 1


Energy capacity of a AA alkaline cell is about 2000 - 2500 mAh. So it will last maybe half an hour. From your experiment, about 50% of power is dissipated on internal resistance of the cell, internally. This power will be about 1.5- 2W. The alkaline battery cell will become pretty hot, but it won't burst into flames or explode. So you should be safe.


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