21. Consider an ideal parallel plate capacitor that is charged. If the capacitor
plates are slightly pulled apart, which of the following statements is correct
during the process? (A) The electric field strength inside the capacitor
decreases. (B) The energy density inside the capacitor increases. (C) The
potential difference between the capacitor plates remains unchanged. (D) The
energy stored in the capacitor increases. (E) The capacitance of the capacitor
increases.