# Equivalent Capacitance in a circuit

## Homework Statement

In the circuit shown in the figure the voltage of the battery is 15.0 V, and the capacitors have the following capacitances: C1 = 2.32 mF, C2 = 2.25 mF, C3 = 4.85 mF, C4 = 4.89 mF
What is the equivalent capacitance of the four capacitors?

http://tinypic.com/r/24dn5oi/8
Two sets of series capacitors that are parallel to each other

## Homework Equations

Ceq=(1/C1+1/C2+1/C3...)^-1 ---- series
Ceq=(C1+C2+C3...) --- parallel

## The Attempt at a Solution

Ceq=(C1+C3)(C2+C4)/(C1+C2+C3+C4)
=(7.17)(7.14) / 14.31
= 3.58 mF

According to online hw system, it's wrong. Is my equation incorrect?

phinds
Gold Member
I think you've got the series/parallel actions backwards. Do capacitors add directly when in series or when in parallel?

CWatters
Homework Helper
Gold Member
Perhaps show us how you got...

Ceq=(C1+C3)(C2+C4)/(C1+C2+C3+C4)

CWatters
Homework Helper
Gold Member
I think you've got the series/parallel actions backwards. Do capacitors add directly when in series or when in parallel?

I don't think that's his problem because his relevant equations..

Ceq=(1/C1+1/C2+1/C3...)^-1 ---- series
Ceq=(C1+C2+C3...) --- parallel

... are correct. Capacitors add in parallel.

phinds
Gold Member
... are correct. Capacitors add in parallel.

Right, which is what led me to wonder how he got a term (c1+c3)

Is the answer near 3.13 mF

NascentOxygen
Staff Emeritus