1.

Consider the circuit consisting of two capacitors having capacitances `3 mu F` and `6 mu F` and an ideal battery of emf e = 4 volts as shown. The switch S is open for a long time and then closed. After the switch is closed. The work done by the battery is : A. 16 m JB. 32 m JC. 64 m JD. 128 m J

Answer» Correct Answer - C
Initial charge on 6 mF capacitor
`= (3 xx 6)/(3+6) xx 4 = 8 mC`
final charge on 6mF capacitor `= 6 xx 6 = 25 mC` charge passing through cell (in direction aided by cell) `= q_(f) -q_(i) = Dq = 24 - 8 = 16 mC` work done by cell = Dqe `= 16 xx 4 = 64 mJ`


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