A2 Daily A Level Physics question
In a lab, a parallel‑plate capacitor is connected to a constant 9 V DC supply. A thin plastic sheet is slid fully into the gap so it fills the space between the plates. Which statement must be true immediately after the sheet is in place?
Answer
The correct answer is C.
Correct: C — The charge on the plates increases while the potential difference stays the same. A battery fixes the potential difference; inserting a dielectric increases the capacitance so more charge flows on at the same voltage. A The battery fixes the voltage, and increased capacitance means more (not less) charge is stored. B With the voltage fixed, increasing capacitance makes the stored energy increase, not decrease (since energy depends on capacitance at constant voltage). C With a constant‑voltage supply, a larger capacitance requires a larger charge to maintain the same potential difference. D The supply fixes the potential difference, so it does not increase when the dielectric is inserted.