Question for electricians

[Tank_Guy#3]

We are on an electricity unit in my PC Troubleshooting class. While testing the currents of various wires inside the case, the subject of negative voltage came up. The teacher was also unsure about it.

So my question to you is: What (in lamens terms) is negative voltage?

 

[Perfection]

Voltage is a measure of how much energy is released when a quantity of charge is moved from terminal A to terminal B in on a device. If it is negative then energy is absorbed instead of released.

One should note that if the voltage from A to B is positive then the voltage from B to A is negative. So the physical meaning of negative voltage and positive voltage are only a matter of what sign convention one chooses on using.

I'm very surprised your teacher didn't know this, it's one of the most elementary electronics concepts.

 

[Leifmk]

I might elaborate a bit: Voltage is a measure of the difference in electric potential between two points. Usually when working with a circuit or other system we choose a common reference point (such as the ground) but there is generally nothing to prevent some other point from having a lower potential.

 

[History_Buff]

Yeah, Perf sums it up pretty good. The thing to remember is that when you go around a complete loop of a circuit, the sum of voltage rises and drop along that path will always be zero.

 

[Perfection]

I might elaborate a bit: Voltage is a measure of the difference in electric potential between two points.

Indeed, that's a more proper broader definition, but I think it's a smidge too abstract for one without basic physics knowledge.