Two capacitors are connected parallel to each other and connected to the battery

Question

Two capacitors are connected parallel to each other and connected to the battery with voltage 30V . Let C1 = 9.1?F ,C2 = 4.6?F be their capacitances. Suppose the charged capacitors are disconnected from the source and from each other, and then reconnected to each other with plates of opposite sign together.

Part A

By how much does the energy of the system decrease?

Express your answer using two significant figures.

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Two capacitors are connected parallel to each other and connected to the battery with voltage 30V . Let C1 = 9.1?F ,C2 = 4.6?F be their capacitances. Suppose the charged capacitors are disconnected from the source and from each other, and then reconnected to each other with plates of opposite sign together.

Part A

By how much does the energy of the system decrease?

Express your answer using two significant figures.

SubmitMy AnswersGive Up

Explanation / Answer

in first case voltage will remian same as V=30 V across both capacitors

Q1=C1V=9.1*10-6*30

Q2=C2V=4.7*10-6*30

in parallel net capacitance=(9.1+4.7)=13.8*10-6 F

U1=CV2/2=13.8*10-6*302/2=6210*10-6 J

total charge Q=Q1+Q2=414*10-6 C

in second case

when capacitiros are in series

net capacitance=(9.1+4.7)/(9.1*4.7)=0.302*10-6 F

charge on each capacitor=Q/2=207*10-6 C

U2=Q2/2C=(207*10-6)2/(2*0.302*10-6)=342*10-6 J

U2-U1=loss in energy=(6210-342)*10-6=5868*10-6 J

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