If R = 2.0 kΩ, C = 4.0 mF, ε = 8.0 V, Q = 20 mC, and I = 3.0 mA, what is the potential difference V_b − V_a? A) +7.0 V B) +19 V C) +9.0 V D) −3.0 V E) −14 V

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Quizplus · Accepted Answer

Using the formula V = Q/C, we can find the voltage across the capacitor: Vc = Q/C = (20 mC)/(4.0 mF) = 5 V. Using the formula for the voltage across a resistor in a circuit with a capacitor: Vs-VR = Vc, we can find the voltage across the resistor: VR = Vs - Vc VR = ε - Vc VR = 8 V - 5 V VR = 3 V Since the voltage drop across the resistor is from left to right, the potential difference between the left and right sides of the circuit (V_b - V_a) is the voltage drop across the resistor, which is 3 V. Therefore, the answer is (C) +9.0 V.

If R = 20 KΩ, C = 4