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Two capacitors of capacities 2C and C are joined in parallel and charged up to potential V. The battery is removed and the capacitor of capacity C is filled completely with a medium of dielectric constant K. The potential difference across the capacitors will now be:

1. V / (K + 2)
2. V / K
3. 3V / (K + 2)
4. 3V / K

Correct answer: 3V / (K + 2)

Solution

When the capacitor with capacity C is filled with a dielectric, its capacitance increases to K*C. The total capacitance of the parallel combination becomes 2C + K*C. The charge remains constant after the battery is removed, and the new potential across the capacitors can be calculated using the formula V = Q/C_total, leading to the result of 3V / (K + 2).

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