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Caclulate capacitance

i have capacitors Cx and C1 (in parallel) and then i have capacitor C2 in series with the (Cx and C1). If C1=4.2 and C2=7.3 what must be the capacitance Cx if the ratio V0 / V1 is 93?
V1 is the voltage accross C1.

c_hockland

ASKER

solution i have tried :

since Cx and C1 are in parallel then the V0 (the V of the circuit ) = V1 = Vx

ozo

I think there must be an unstated assumption.
Cx could be anything and you could sill make V0 / V1 anything you want my putting an appropriate charge between Cx/C1 and C2

c_hockland

ASKER

so , any ideas how i could start??

ozo

I think you need another assumption. for example that you started with V0 = V1 = 0 and then applied V0 to the circuit, in which case the ratio
( 1/(Cx+C1) + 1/C2) / (1/(Cx+C1)) = V0 / V1

JR2003

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Capacitors/ParSeriesCap.html

The capacitance of the parallel part of the circuit is C1 + Cx
We know the following facts:
Q = C/V
Q1 = Q2
V0 = V1 + V2

so we know that
(C1+Cx)/V1 = C2/V2

I take it you don't actually mean that V0/V1 = 0.93 as V0 is bigger than V1?
I'll asume you really mean that V1/V2 = 0.93?
so
V1/V2 = (C1 + Cx)/C2
so
Cx = C2(V1/V2) - C1

c_hockland

ASKER

well JR 2003 , "the question just states that the Ratio V0/V1 is to be 93" . I guess it means that V0 =93V1 . Does anything changes in the solution ?

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JR2003

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c_hockland

ASKER

great! Thanks so much JR2003