1 Reply Latest reply on Oct 15, 2020 1:11 AM by michaelkellett

# Resistors in parallel

I know this seems simple, it probably is. But I keep getting told that the first two resistors in this circuit (namely the 10k and 15k resistors) are in parallel and I just don't see it. The def of a parallel resistor is one that is attached across another resistors in a way that the both have the same voltage drop. The 10k is going to get a different voltage than the 15k because the 10k is in series with the source. Any help would be great.

• ###### Re: Resistors in parallel

It's because a voltage source has an impedance or resistance of zero. So for impedance analysis you can set it to zero.

Thevenin's theorem also states that you can replace a voltage source in series with a resistor with a current source in parallel with that resistance (or vice versa) - and everything works the same.

There is a Wiki article (and lots of other stuff on the web Google Thevenin Theorem and Norton Theorem and Kirchoff for the full set of key linear circuit theorems).

But you are correct - the resitors are NOT in parallel, it is that the combination of voltage source and resistors can replaced by a single resistor (value = the two in parallel) and a voltage source (which will have a different voltage from the original source).

I can't draw diagrams from here but there are lots on the web.

MK