Electrostatics Question 109

Question: A body of capacity 4μF is charged to 80V and another body of capacity 6μF is charged to 30V. When they are connected the energy lost by 4μF capacitor is [EAMCET 2001]

Options:

A) 7.8 mJ

B) 4.6 mJ

C) 3.2 mJ

D) 2.5 mJ

Show Answer

Answer:

Correct Answer: A

Solution:

Initial energy of body of capacitance 4 mF is Ui=12×(4×106)(80)2=0.0128J

Final potential on this body after connection is V=4×80+6×304+6=50V.

So final energy on it Uf=12×4×106(50)2=0.005J

Energy lost by this body =UiUf= 7.8mJ



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