# Confusion about the "+ v -" notation

Discussion in 'General Electronics Chat' started by Ulfalizer, Jan 16, 2009.

1. ### Ulfalizer Thread Starter New Member

Jun 29, 2005
5
0
Hi,

How exactly does the "+ v -" notation for specifying the voltage across a component (e.g. a resistor) work? Is the + side always oriented towards the + side of the voltage source, so that it's just a mnemonic for remembering what direction current goes in, or is there some deeper meaning? Will exchanging + and - result in a nonsensical schematic?

/Ulf

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
Machs nichts across a resistor, but polarity becomes very significant relative to a sensitive component like a transistor, diode or polarized capacitor.

3. ### mik3 Senior Member

Feb 4, 2008
4,846
63
For batteries and power sources the positive side is the side where the current goes out of the battery or power source. For resistors and other components (active or passive) the positive side will be on the side where the current enters the component. Take care of capacitors and inductors because sometimes they act like sources and sometimes like passive components.

Last edited: Jan 16, 2009
4. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
The "+" corresponds to the point of higher potential; whereas the "-" corresponds to the point of lower potential - with respect to the component.

Dave

5. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
And for us grunt techs potential is another word for voltage. Engineers

6. ### italo New Member

Nov 20, 2005
205
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A [+] does not signify a higher-lower anything but is does imply a current flow direction mainly electrons as opposed to holes.

7. ### Ulfalizer Thread Starter New Member

Jun 29, 2005
5
0
I think you've cleared it up for me. Thanks!

/Ulf

8. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Which is a function of the potential and is a notation dependant on whether current is defined in terms of conventional or electron flow. Defining it in terms of flow direction of electrons and holes is nonsensical in the case of many passive devices. Remember the OP is asking about the + and - notation for voltage specification across a component; I think you are think about the + or - notation sometimes applied to certain active devices.

IMO it is a clumsy notion, but some (still) use it.

Dave