A 5.0 A current is set up in a circuit for 6.0 min by a rechargeable battery with a 6.0 V emf. By how much is the chemical energy of the battery reduced?
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Solution
The chemical energy of the battery is reduced by ΔE=qε, where q is the charge that passes through in time Δt=6.0 min, and ε is the emf of the battery. If i is the current, then q=iΔt and
ΔE=iεΔt=(5.0A)(6.0V)(6.0min)(60s/min)=1.1×104J
We note the conversion of time from minutes to seconds.