Calculating Potential Difference in Parallel Circuits

[looi76]

Homework Statement

http://img241.imageshack.us/img241/1087/09052008hf9.png
What is the potential difference across (i) AB (ii) BC.

Homework Equations

??

The Attempt at a Solution

(i) $$\frac{200}{400} \times 6 = 3V$$

Is this right?

 

[BishopUser]

I think the easiest way to do this would be to use equivalent resistances to find the current. After that it is very easy

 

[looi76]

I didn't understand...

 

[alphysicist]

Hi looi76,

We know the total resistance between A and B is 200 ohms. What is the total resistance between B and C?

 

[looi76]

The total resistance between B and C is 100 because they are connected in parallel. So, $$\frac{200}{(100 + 200)} \times 3 = 2V$$

Is this correct?

 

[Defennder]

No, that is not the total resistance between B and C. They are both in parallel. What is the formula for resistance connected in parallel?