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Using a battery, a 100 pF capacitor is charged to 60 V and then the battery is removed. After that, a second uncharged capacitor is connected to the first capacitor in parallel. If the final voltage across the second capacitor is 20 V, its capacitance is

Asked in JEE Main 3rd April 2nd Shift 2025 · Redistribution of charge

Answer: (3) 200 pF

Step-by-step solution

Initial charge on the first capacitor: Q=C₁V₀=100×60=6000 pC, and this total is conserved because the battery has been removed.

In parallel the two capacitors share a common final voltage, and we are told it is 20 V.

Charge left on the first: q₁=100×20=2000 pC, so the charge that moved to the second is q₂=6000-2000=4000 pC.

C₂=(q₂)/V=(4000)/(20)=200 pF.

Why the other options are wrong

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