A particular 12 V car battery can send a total charge of 84 A • h (ampere-hours) through a circuit, from one terminal to the other. (a) How many coulombs of charge does this represent? (b) If this entire charge undergoes a change in electric potential of 12 V, how much energy is involved?

#### Solution:

An ampere is one coulomb per second and 1 hour = 3600 seconds.

\therefore 1A=1\frac{C}{s}

a)84A\cdot h = \left(84\frac{C\cdot h}{s}\right)\left(3600\frac{s}{h}\right) = 3.0\times10^{5}C

a)84A\cdot h = \left(84\frac{C\cdot h}{s}\right)\left(3600\frac{s}{h}\right) = 3.0\times10^{5}C

b)Change in potential energy is \triangle U = q\triangle V = (3.0 \times 10^{5} C)(12 V) = 3.6 \times 10^{6} J

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