# Ohm's Law Question

A battery charger is connected to a dead battery and delivers a current of 7.5 A for 3.5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

I'm not exactly sure what I am doing wrong. I understand that we have to use Ohm's Law in this question. So doing that, I took the given current, and converted it into the total number of coloumbs used over the 3.5 hours. I then calculated the resistance, and then I multiplied the total coloumbs by the resistance, and got joules (151,200). That's wrong, so I'm not sure where I went wrong.

I'd appreciate any help. Thanks.

tigerguy said:
A battery charger is connected to a dead battery and delivers a current of 7.5 A for 3.5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

I'm not exactly sure what I am doing wrong. I understand that we have to use Ohm's Law in this question. So doing that, I took the given current, and converted it into the total number of coloumbs used over the 3.5 hours. I then calculated the resistance, and then I multiplied the total coloumbs by the resistance, and got joules (151,200). That's wrong, so I'm not sure where I went wrong.

I'd appreciate any help. Thanks.

use $$E = P \cdot t = U \cdot I \cdot t$$ with t in seconds.