Question

Suppose that a 12-volt automobile battery

with 100 amp-hour capacity is fully charged.
How much energy (in joules) is stored in the
battery?

Answer 1

4.32 megajoules or 4,320,000 Joules

First we need to understand what a joule is.

A joule is a measure of energy, and is equal to the watt.

1 Joule = 1 Watt, 1 kJ = 1kW

Finding the total amount of energy a supply can produce is the same for Watts and Joules. Volts and Amps are measured per second, so if you measure 120V from a conductor, thats 120V per second.

A 100Ah battery can produce 100A per hour, and there are 3600 seconds in an hour.

Energy = Joules = Volts * Amps * Time

3600 * 100A * 12V = 4.32 megajoules (4,320,000 J)

the same number can also be found this way:

100A * 12V = 1200 * 3600 = 4.32 megajoules