KVL loop: Example wrong, or did I misunderstand?

[EngnrMatt]

In my circuit analysis textbook, there is an example problem using a KVL loop. Though it seems relatively simple, I cannot understand the answer.

the loop consists of 3 voltages: -8, 12, and the unknown, Vr2. The polarities (clockwise) around the loop are respectively +,-,+.

The answer given is 4V for Vr2. I can see this being the case if the 8 wasn't negative, but if I apply algebra, the equation comes out as:

+ (-8) - (12) + Vr2 = 0

where Vr2 = 20

Am I treating the -8 wrong? Because if it were positive 8, I could understand Vr2 being 4, however, I am given to understand negative voltage is different from positive voltage.

 

[SteamKing]

A circuit diagram would be helpful.

 

[Simon Bridge]

One of those is a voltage source while the other two are the volt drops over resistances huh?

 

[CWatters]

Post the circuit diagram otherwise we are guessing what might be wrong.

 

[rezeew]

I would say that it is possible that the example problem in your textbook is incorrect or there may be a misunderstanding on your part. It is important to carefully check the values and polarities of the voltages used in the KVL loop before solving the equation. In this case, it appears that the -8 voltage may have been mistakenly written as positive, leading to the incorrect answer of 4V for Vr2. It is also important to note that negative voltages are indeed different from positive voltages and should be treated accordingly in the KVL equation. I would suggest double-checking the problem and potentially consulting with your instructor or a classmate for clarification.