A parallel plate capacitor is charged by a battery. Which of the following quantities remains UNCHANGED when a dielectric slab is inserted while the battery remains connected?
Answer and explanation
Correct answer: B. Potential difference between the plates
- Step 1: The terminal voltage of the battery dictates the potential difference across the capacitor plates as long as it remains physically connected.
- Step 2: Therefore, the potential difference is fixed and remains completely unchanged.
- Step 3: In contrast, capacitance increases (), charge increases (), and stored energy increases ().
Answer
Potential difference between the plates.
Why not the others: Electric field decreases inside the dielectric if charge is fixed, or stays constant only if is constant and , but potential difference is the direct invariant; Charge increases by factor ; Stored energy increases by factor .
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