Question

The drawing shows two fully charged capacitors (C1 = 7 µF, q1 = 4 µC; C2 = 16 µF, q2 = 4 µC). The switch is closed, and charge flows until equilibrium is reestablished (i.e., until both capacitors have the same voltage across their plates). Find the resulting voltage across either capacitor

Answer 1

you have 8microC total charge.

You have 23microF capacitance.

Voltage= Qtotal/C=8/23 volts.

on C1, q=C1*8/23=7micro*8/23=56/23 micro F
on C2, q=16micro*8/23=128/23 microC

adding q1+q2, 184/23 microF=8microF

Answer 2

Depending on which way they are wired:assume they are wired positive plate to negative plate of each other.

Then Qeff=16*4-7*4=36uC.(If wired positive plate to positive plate then charges will add up)

This charge will get redistributed.

Applying conservation of charge:

Qeff=(C1+C2)Vfinal

Vfinal=1.56v

Answer 3

The first answer is correct...final voltage will be: Qtotal/(C1+C2)=0.347