A 12 V battery is charged for 20 minutes by connecting it to a source of electromotive force
(e.m.f.). The battery is supplied with 7.2 × 104
J of energy in this time.
How much charge flows into the battery?
A. 5.0 C B 60 C C 100 C D 6000 C
answer is D but how?

Question

A 12 V battery is charged for 20 minutes by connecting it to a source of electromotive force
(e.m.f.). The battery is supplied with 7.2 × 104
J of energy in this time.
How much charge flows into the battery?
A. 5.0 C B 60 C C 100 C D 6000 C
answer is D but how?

anonymous · Answer

E = (1/2) q V, charging of capacitor similar to charging a battery?

q = 2 E / V = 2(72000)/12 = 12000 

apparently, this analysis is wrong, but I don't  see why.

E = q V would have given q = E/V = 6000, their answer

I guess because the energy storage is due to chemical change rather than capacitance E = q V.