Question

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is then slipped between the plates, which results in:

• A. Reduction of charge on the plates and increase of potential across the plates
• B. Increase in the potential difference across the plates,reduction in stored energy, but no change in the charge on the plates
  
• C. Decrease in the potential difference across the plates reduction in stored energy, but no change in the charge on the plates
  
• D. None of the above

Answer 1

The correct option is C

Decrease in the potential difference across the plates reduction in stored energy, but no change in the charge on the plates

The charge on the plates does not change as the capacitor is disconnected from the battery. The presence of dielectric slab increases the capacitance, which decreases the potential difference. Thus, the energy stored is reduced.