If R = 4.0 kΩ, C = 3.0 mF, ε = 15 V, Q = 12 mC, and I = 2.0 mA, what is the potential difference Vb − Va?
A)+3.0 V
B)−19 V
C)−3.0 V
D)+27 V
E)+21 V

Question

If R = 4.0 kΩ, C = 3.0 mF, ε = 15 V, Q = 12 mC, and I = 2.0 mA, what is the potential difference Vb − Va? 
A)+3.0 V 
B)−19 V 
C)−3.0 V 
D)+27 V 
E)+21 V

Quizplus · Accepted Answer

The potential difference Vb − Va can be calculated using the formula:
Vb − Va = ε − IR − Q/C

Substituting the given values:
Vb − Va = 15 V − (2.0 mA)(4.0 kΩ) − (12 mC)/(3.0 mF)
Vb − Va = 15 V − 8 V − 4 V
Vb − Va = 3.0 V

Therefore, the potential difference Vb − Va is -3.0 V, or choice C.

If R = 40 KΩ, C = 3