A parallel-plate capacitor with air between its plates is charged by connecting it to a DC power supply, and is then disconnected.
The plates of the capacitor are then pulled further apart so that their separation is doubled.
Which of the following statements is correct?
The capacitance of the capacitor doubles.
The electric field strength between the plates doubles.
The energy stored by the capacitor doubles.
The potential difference across the plates is halved.
