# What is infinite resistance?

Discussion in 'General Electronics Chat' started by Gdrumm, Feb 9, 2009.

1. ### Gdrumm Thread Starter Distinguished Member

Aug 29, 2008
684
36
I'm trying to solve a series circuit question from my DC Circuits class homework, and I can't seem to recall what infinate resistance means.

Here is the info I have on the circuit.
E=40v, R1=5ohms, R2=10ohms, R3= Infinate ohms.

I see the answer in the back of the book, but I don't know how they got it.

I'm solving for E Total, I Total, R Total, and P Total.

I'm guessing that infinate resistance means there is a short?
Thanks, Gary

2. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,047
295
Nope...infinite resistance means the component (resistor) does not exist. You may safely remove it from your schematic with no danger of punishment

3. ### Gdrumm Thread Starter Distinguished Member

Aug 29, 2008
684
36
Thanks,
But I'm still curious, because in the answer section of my workbook, it shows Total I=0 amps, meaning that R3 in effect neutralized R1 and R2.

So, does this look accurate?
ET = 40v
IT = 0A
RT = 00 ohms
PT = 0 watts

What does "fail open" mean?
I found that on this site, Vol 1, Chapter 5/7.
It implies that a resistor might "fail open", increasing it to near infinate levels.
Thanks, Gary

Last edited: Feb 9, 2009
4. ### mik3 Senior Member

Feb 4, 2008
4,846
63
If the resistors are connected in series then no current will flow due to the infinite resistance (open circuit).

if the resistors are connected in parallel then current will flow only through R1 and R2.

5. ### flat5 Active Member

Nov 13, 2008
403
17
"fail open" means resistor has been destroyed. It has failed.
In this case, "fail open", it does not pass any current anymore.
It is a dead resistor. Don't try to return it to the store where you bought it.

See "Monty Python Dead Parot Sketch".

6. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
6
I=E/R, so as R increases, I diminishes. As R increases without bound, I approaches zero. Once R is a few zillion yotta-Ohms, I is a few zillionths of a yocto-Ampere.

7. ### blhoward New Member

Feb 4, 2009
5
0
Infinite resistance is open circuit (burnt resistor in real life) no current will flow, zero ohms is short circuit.
Lets not confuse.
Brian