Electrostatic Potential And Capacitance

Correct options: (A) and (D)

Explanation:
Step 1: When the switch is closed
- Capacitors A and B are connected in parallel to a battery with voltage .
- Each capacitor has capacitance .
- Total energy stored:

⇒ Option (A) is correct.

Step 2: When the switch is opened
- Now, both capacitors are disconnected from the battery. - A dielectric of constant is inserted into both.

Capacitor A (isolated):
- Initial charge: (remains unchanged)
- New capacitance:
- New voltage:
- Energy stored:


Capacitor B (still connected to battery during dielectric insertion):
- Voltage remains
- Capacitance becomes:
- Energy stored:


Total energy:

⇒ Option (D) is correct.

Option (B) is incorrect because capacitor B is connected to the battery and stores charge.
Option (C) is incorrect in this context, because energy in capacitor B is , but the question implies it's disconnected — which contradicts.