Electrostatics Question 614

Question: Two identical capacitors, have the same capacitance C. One of them is charged to potential V1 and the other to V2 . The negative ends of the capacitors are connected together. When the positive ends are also connected, the decrease in energy of the combined system is [IIT-JEE (Screening) 2002]

Options:

A) 14C(V12V22)

B) 14C(V12+V22)

C) 14C(V1V2)2

D) 14C(V1+V2)2

Show Answer

Answer:

Correct Answer: C

Solution:

Initial energy of the system

Ui=12CV12+12CV22

When the capacitors are joined, common potential V=CV1+CV22C=V1+V22

Final energy of the system

Uf=12(2C)V2=122C(V1+V22)2=14C(V1+V2)2

Decrease in energy = UiUf=14C(V1V2)2



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