Electromagnetism - Capacitor

Two capacitors of capacitance 1.0 microfarad and 2.0 microfarad are each charged by being connected across a 5.0-volt battery. They are disconnected from the battery and then connected to each other with resistive wires so that plates of opposite charge are connected together. What will be the magnitude of the final voltage across the 2.0-microfarad capacitor?
A. 0V
B. 0.6V
C. 1.7V
D. 3.3V
E. 5.0V

(GR9677 #62)

Solution:
Fig 1: Initial configuration.

The charges stored at each capacitor when they are connected across 5.0-V battery:



Fig 2: At the instant after reconnection (the plates of opposite charge are connected together)


Fig 3: In equilibrium

A short time later after reconnection, the net charge is conserved but redistributed between the two capacitors until the potential across them reaches equilibrium (the same).

Thus, the net charges on the upper and lower plates are:



And,


To find ,take the upper plate:




Answer: C