A parallel-plate capacitor containing a dielectric slab is connected to a cell. The slab is then taken out of the capacitor slowly. Disregard the forces of gravity and friction. For this process, which of the following statements is incorrect?
(a) The external agent pulling the slab out will have to perform some work.
(b) The potential energy of the capacitor will decrease.
(c) The cell will receive some energy.
(d) The work done on or by the external agent will be equal to the energy supplied or absorbed by the cell.
