If I = 2.0 A in the circuit segment shown below, what is the potential difference VB − VA?
A)+10 V
B)−20 V
C)−10 V
D)+20 V
E)+30 V

Question

If I = 2.0 A in the circuit segment shown below, what is the potential difference VB − VA? 
A)+10 V 
B)−20 V 
C)−10 V 
D)+20 V 
E)+30 V

Quizplus · Accepted Answer

Using Kirchhoff's voltage law, we can write:

−12 + 2R + VA + 4(VA − VB) = 0

Simplifying: 
−12 + 2R + 5VA − 4VB = 0 
5VA − 4VB = 12 − 2R

Next, using Ohm's law, we know that:

VA − VB = IR

Substituting in our given values, we get:

2R − 5(IR) = 12 − 2R 
4R − 5IR = 12

Solving for IR, we get:

IR = −2.4 V

Therefore, VB − VA = −IR = −(−2.4) = −2.4 V

So the correct answer is (C) −10 V.

If I = 20 a in the Circuit Segment Shown Below, What Is