KVL loop: Example wrong, or did I misunderstand?

  • Thread starter Thread starter EngnrMatt
  • Start date Start date
  • Tags Tags
    Example Kvl Loop
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
3 replies · 2K views
EngnrMatt
Messages
34
Reaction score
0
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.
 
Physics news on Phys.org