Finding Current, charge, and energy

Thread Starter


Joined Sep 1, 2008
Hi, i need help with my homework, i did problems 1,2,5 out of the 5, if someone could check my solutions of the problems i already did. 3 &4 i don't know how to solve them if someone could help me there to please. Help is appreciated.


Last edited:


Joined Mar 20, 2007

1) The answer is wrong. You have to figure out the wattage first. So what is the wattage of 500MJ per week? A watt is a joule/sec. How many seconds in a week? Convert to watts and then divide by the voltage like you tried to do.

2) The answer is correct. A straightforward integration of the current over time.

3) Current is the derivative of charge with respect to time, right?

4) Same as problem #2 without the exponential function. Amps is the coulomb rate per second, one hour is the time. How many seconds in an hour? How many coulombs come out of the battery in a hour? Volts is the energy density of the charge in joules/coulomb. How much energy is in the total coulombs?

5) Fairly straightforward. If the battery pushes the charge, that is minus absorption. If the battery receives the charge, it is plus absorption.