# Homework Help: Capacitance, unbalanced wheatstone.

1. May 27, 2015

### Suraj M

1. The problem statement, all variables and given/known data

Find capacitance across AB
So i divided the current into q1 and q2 as shown. then i assumed that q₂>q₁.

2. Relevant equations
$C=\frac{Q}{V}$
I dont know anything after KVL KCL and loop law.

3. The attempt at a solution
So i split the current at T into q₃ and q₂-q₃
by the diagram, i used Loop law for UPQTU and QRSTQ.
this gave me a relation between q₁,q₂ and q₃.
i got
$$q₁= 15q₃$$
$$q₂=16q₃$$
$$q₁ = \frac{15}{16} q₂$$
using these, i used the equation..
$$C_{AB} = \frac{q₂ +q₁}{\frac{q₁}{5} + \frac{10}{q₁+q₃}}$$
so i got $$C_{AB} = \frac{155}{23} µF$$
Is this right.? because i doubt it.

2. May 27, 2015

### ehild

You work with charges instead of currents. The net charge should be zero at junctions Q and T.

3. May 27, 2015

### Suraj M

can't we do it by this method? KCL necessary? I will try.

4. May 27, 2015

### ehild

You can, but write charge instead of current. And take into account that the net charge on the connected plates is zero, and the charges on the opposite plates of a capacitor are of opposite sign.

Show your work in detail. Otherwise I can not decide if you got the correct result or not.