[Discussion Unit 6] Energy Math

(This question has been modified from The College Board’s Energy Primer for APES Students)

Batteries are usually rated in terms of ampere-hours, indicating the current that the cell is capable of delivering for a specified time. A typical AA flashlight battery, for instance, might be rated at 2.8 ampere-hours. The total electrical energy available from such a battery is found by multiplying the ampere-hour rating by the battery voltage. Thus this same 1.5 volt AA battery could deliver 4.2 watt-hours of electrical energy.

Convert this energy to kWh and compare the cost of electrical energy derived in this manner to that of standard “grid-based” electricity. Assume that the battery costs $0.50 and that electricity from the power company is available at $0.12/kWh.

In order to answer, type out your work.

($0.12kWh • 4.2hours) + $0.50
=$1.004 or $1.00

1 Like

(14.2/1000)=0.0142 -> convert to Kwh
0.0142•0.12=0.001488 -> 12¢ per Kwh
0.001488+0.50=0.501488 -> 50¢ for battery
0.501488¢ or .50¢ -> my answer
I think I did this wrong because the actual cost for the Kwh was almost 0.

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