# Voltage between two points

1. Dec 10, 2012

### tomkoolen

A battery has a voltage of 107.5 V. We denote this battery with point B. Point C is the point after two resistors, which are parallel to one another. Immediately after point C we get one more resistor. Calculate the voltage between B and C.

I calculated the total resistance between B and C and from there, I calculated the voltage. However my teacher says that I should take resistor 3, which is situated after point C. Is it just me, or is he wrong?

2. Dec 10, 2012

### CWatters

It's hard to interpret what your circuit looks like from the description but it looks like

Battery +ve --- Point B --- 2 resistors in parallel --- Point C ---- one resistor --- Battery -ve

If that is correct..

Step 1 Convert the two resistors in parallel to one..

Battery +ve --- Point B --- one resistor(R1) --- Point C ---- one resistor(R2) --- Battery -ve

Then the voltage at point C with respect to the battery -ve can be calculated using the potential divider rule..

Vc = Vbat * R2/(R1+R2)

The voltage requested Vb-Vc = Vbat - Vc = Vb - (Vbat * R2/(R1+R2))