# How to calculate Potential Difference between 2 random points in a circuit? [closed]

This might be a very easy question to solve for a lot of you but I was having an extremely hard time evaluating the potential difference between points A and B. Thats why I decided to just post this question.

Consider the circuit shown in the figure -

(A) The current in the $$5 \Omega$$ resistor is $$2A$$

(B) The current in the $$5 \Omega$$ resistor is $$1A$$

(C) The potential difference $$V_A - V_B$$ is $$7V$$

(D) The potential difference $$V_A - V_B$$ is $$5V$$

For finding the current through the $$5 \Omega$$ resistor I just found the net resistance and then used $$I = {V \over R}$$ (Ohm's Law). For PD I tried using the Voltage division rule on both points A and B. However, that technique didn't work. I saw the solution of this question and my book used KVL to solve it. I don't want to use that method to solve the question unless I HAVE to. So, can anybody show how to solve this; preferably using Voltage Division Rule? (I'm open to other ways too)

## 1 Answer

Voltage division applies when you know the voltage at the ends of two series resistors and finds the voltage at the node between them. You have to simplify the circuit to contain such a form before you can use it. I.e. you need to simplify the circuit until it looks like this.

Now, you can reuse your knowledge of the current through the resistors on the left. Find the voltage at B and the node above B, and A will be somewhere in between by division.