CBSE Class 12 · 2011 · CapacitanceShort Answer

Net capacitance of three identical capacitors in series is

1 μ F

. What will be their net capacitance if connected in parallel? Find the ratio of energy stored in the two configurations if they are both connected to the same source.

Answer: Parallel capacitance $= 9 μ F$ ; ratio of energy stored (series : parallel) $= 1 : 9$ .

Solution

For three identical capacitors

C

in series:

\frac{1}{C _{s}} = \frac{3}{C} = \frac{1}{1 μ F}

C = 3 μ F

In parallel:

C_{p} = 3 C = 9 μ F

At the same source voltage

V

, energy

U = \frac{1}{2} C V^{2} \propto C

, so:

\frac{U _{s}}{U _{p}} = \frac{C _{s}}{C _{p}}

\frac{U _{s}}{U _{p}} = \frac{1}{9}

CBSE Class 12 Board · 2011 · Subjective

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