Member • Nov 30, 2010
Series and parallel circuits
why cant it be sum of their individual capacitance as in case of resistors and inductors?
Plz explain this contrary in terms of Parallel circuits too....
Member • Nov 30, 2010
Member • Nov 30, 2010
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Member • Dec 2, 2010
Superb Explanation !reachrkataThere are 2 ways to understand this -
1) Consider the voltage equation of a cap V = 1/C * (integral) i.dt. if there are 2 caps in series you have V1 = 1/C1 * (integral) i.dt and V2 = 1/C2 * (integral) i.dt. Total voltage V = V1+V2 = (1/C1+1/C2) * (integral) i.dt. Now if we have an effective cap Ceff such that the same current i flows through it, V = 1/Ceff * (integral) i.dt. Equating these two you get 1/Ceff = 1/C1 + 1/C2.
2) Adding capacitors in series is like having a single cap with the same plate area as the individual caps and distance between plates as sum of distances of individual caps. That is if C1 = EA/d1, C2 = EA/d2, Ceff = EA/(d1+d2) where E = dielectric constant.
Solve th above equations and you again get 1/Ceff = 1/C1 + 1/C2
For paralle circuits, instead of adding voltages you have to add currents (I = CdV/dt) and you get Ceff = C1+C2.
-Karthik
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