The capacity of a storage battery, such as those used in automobile electrical systems, is rated in ampere-hours (A⋅h). A 50 A⋅h battery can supply a current of 50 A for 1.0 h, or 25 A for 2.0 h, and so on.

What total energy can be supplied by a 13 V, 60A?h battery if its internal resistance is negligible?

2.80 MJ  

Explanation:

(a) We want to calculate the energy U of the battery, where its voltage is E = 13.0V and the supplied current is I = 60 A. We can neglect the internal resistance, so the terminal voltage equals the emf of the battery V = 13.0V. The quantity of delivered energy is given by the rate at which energy is delivered to it in a certain time t. We could obtain the rate at which energy is transferred by using equation , where the rate represents the power P = IV. Therefore, the energy produced is given by  

U = P*t                                                (P = IV)            

U = I*V*t                                                                     (1)  

Now we can plug our values for I, V and t into equation (1) to get the energy produced in time t = 1 h = 3600 s  

U = I*V*t = (60 A)(13 V)(3600s) =  2.80 MJ  

this is poiselle's equation from fluid mechanic in physics. mech eng