Question

A battery charger is connected to a dead battery and delivers a current of 3.5 a for 4 hours, keeping the voltage across the battery terminals at 16 v in the process. how much energy is delivered to the battery?

Answer 1

The power delivered is equal to the product between the voltage V and the current I:
$P=VI=(16 V)(3.5 A)=56 W$

This power is delivered for a total time of $t=4h=4 \cdot 3600 s = 14400 s$, so the total energy delivered to the battery is
$E=Pt = (56 W)(14400 s)=806400 J=806.4 kJ$