Question

Four identical capacitors are joined in series, across a battery of \(20\ \text{V}\). The capacitors are separated and then connected in parallel. The potential difference across the parallel combination is

• A. \(20\ \text{V}\)
• B. \(10\ \text{V}\)
• C. \(5\ \text{V}\)
• D. \(15\ \text{V}\)

Hint:

In series each capacitor gets an equal share of 20 V. When reconnected in parallel with like plates together, the common potential is the same as each capacitor's own.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
Four identical capacitors in series share the supply equally, so each has \(\dfrac{20}{4}=5\ \text{V}\) and charge \(q=5C\).

Step 2: Parallel connection
After they are separated and joined in parallel (like plates together), the total charge is \(4q\) and the total capacitance is \(4C\).

Step 3: Calculation
\(V=\dfrac{4q}{4C}=\dfrac{q}{C}=5\ \text{V}\)

Final Answer:
The potential difference across the parallel combination is 5 V. \[ \boxed{\text{(C) }5\ \text{V}} \]