# Battery with internal resistor

1. May 9, 2008

### jimmyting

[SOLVED] Battery with internal resistor

1. The problem statement, all variables and given/known data
What is the current in a 8.25 ohm resistor connected to a battery that has a .21 ohm internal resistance when the potential drop across the terminals of the battery is 6V?

2. Relevant equations
$$R_{s}=R_{1}+R_{2}...$$

$$V=IR$$

3. The attempt at a solution
So I believe that the internal resistor can just be considered being in series to the other resistor, allowing me to calculate the equivalent resistor. Then with that, using V=IR, I thought I was able to get the current flowing through the circuit. I got .70921 A
Can someone correct my train of thought?

2. May 9, 2008

### Hootenanny

Staff Emeritus
Note that the potential drop across the terminals includes the internal resistance of the battery. The internal resistance of a battery may be depicted thus,

So the actual emf of the battery is the 6V plus the voltage drop across the internal resistance. Do you follow?

Image courtesy of Hyperphysics

Last edited: May 9, 2008
3. May 9, 2008