Question

If the potential difference between the plates of a charged and isolated parallel-plate condenser of capacitance 1 μF changes from 12 V to 4 V when a dielectric slab of dielectric constant K is introduced to fill the entire space between the plates, then

• A. The change in the charge on the capacitor is 8 µC
• B. The change in the capacity is 3 µF
• C. The electric field in the capacitor increases by 100 %
• D. The value of K is 3

Answer 1

The correct option is D

The value of K is 3

In isolated condenser the charge is conserved. Introducing the dielectric increases the capacity from C to KC, decreases the potential from V to V/K. The electric field decreases from E to E/K