# Shorted Resistor Problem

Discussion in 'Homework Help' started by yan500, Jul 24, 2011.

1. ### yan500 Thread Starter Member

Jul 12, 2011
48
0
Hi all, I'm having an issue with Question 33 on this worksheet: http://www.allaboutcircuits.com/worksheets/dc_sp.html

I understand why the effects occur in R1, R3 and R4 but why does the voltage dropped across R2 decrease? Isn't the voltage in a parallel circuit equally dropped? So if Vr3 increases and Vr4 decreases doesn't that balance out and leave Vr2 unaffected or at least increased voltage dropped?

Help is much appreciated.

2. ### praondevou AAC Fanatic!

Jul 9, 2011
2,939
489
R2 is in parallel with R4 and R3 which are in series. So the same voltage drop you have on R3 - R4 you have on R2. Decreasing the resistance by shorting R4 will decrease the total voltage drop on R3 - R4, therefore decrease the voltage drop on R2.

You increase the current through R1 but this current is then divided into to branches, so this does not balance out.

I think the easiest is to put real values in the circuit and then calculate what happens.

yan500 likes this.
3. ### yan500 Thread Starter Member

Jul 12, 2011
48
0
Thanks a lot! The reason I didn't put real values into the circuit was due to the problem being a test of qualitative analysis.