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

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Quizplus · Accepted Answer

Using Kirchhoff's Voltage Law (KVL), we can write: - V_B + V_A - I*R = 0 where R is the resistance of the segment U1B1BS1U1. Since the current I is flowing from U1 to B1, the potential at U1 (relative to B0) is higher than at B1, so we can write V_A = +10V. Similarly, the potential at B1 (relative to B0) is higher than at S1, so we can write V_B = -10V. The resistance R can be found using Ohm's Law: R = V/I = (-20V - (+10V))/2.0 A = -15V/2.0 A = -7.5 ohms Since resistance cannot be negative, we made a mistake somewhere in our calculations. The most likely error is assuming that the current I is flowing from U1 to B1, when in fact it is flowing in the opposite direction. Reversing our current direction and repeating the calculations gives: - V_B + V_A + I*R = 0 V_A = +10V (as before) V_B = -10V (as before) R = - V/I = (-10V - (+10V))/(-2.0 A) = 0 ohms So the correct answer is C) -10V.

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