# Homework Help: Physics Help: Electricity & Circuits

1. Apr 18, 2004

### MJ

I have a test tomorrow and i'm having trouble figuring out some of these review problems. Any help would be much appreciated!

1) Find the power dissipated by R3 in a series circuit with a 12V battery with 3 resistors. R1=45ohms R2=200ohms R3=700ohms

I also have a few questions where it asks you to find the potential difference between two points. For example, before and after a resistor in a circuit. How do i do this?

Thank you very much!

2. Apr 19, 2004

### toosm:)ey

Remember that P=IV

You have the total voltage, find the total resistsance. Then find how much voltage is used in R3.

3. Apr 19, 2004

### faust9

Also, $P=I^2R$. don't forget (or at least learn how to use Ohm's law) all of the power equations. Find total resistance. You should be able to find the circuit current then apply the above eq. Good luck on the test.