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

 

Machs nichts across a resistor, but polarity becomes very significant relative to a sensitive component like a transistor, diode or polarized capacitor.

 

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.

 

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

The "+" corresponds to the point of higher potential; whereas the "-" corresponds to the point of lower potential - with respect to the component.

Dave

 

And for us grunt techs potential is another word for voltage. Engineers

 

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

 

I think you've cleared it up for me. Thanks!

/Ulf

 

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

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