1. A parrallel plate capacitor contaqins a ice sheet (thickness 0.5*10^-3m). The dielectric constant of mica is 8 and that of the fibre is 2.5. Assuming that the fibre breaks down when subjected to electric field 6.4*10^6V/m. Find the maximum safe voltage that can be applied to the capacitor .                

 

2.The distance between the plates of a parralel plate capacitor is 0.5m. A field of 3*10^4V/m is established between the plates. It is then disconnected from the battery and an uncharged metal plate of thickness 0.01mis inserted into the capacitor parallel to its plates.Find the potential difference between the plates.  (a)before the induction of the metal plate                                                          (b) after its introduction. What would be the potential difference if a plate of dielectric constant K = 2 is introduced in place of metal plate.?

 

3. The capacitence of a variable ratio capacitor can be changed from 50pF by turning the dial from 0degree to 180degree. Withthe dial set at 180degree,the capacitor is connected to a 400V battery. After charging, the capacitor is disconnected from the battery and the dial is turned to 0degree.                  

(a) What is the potential difference between across the capacitor when the dial read 0degree.

(b)How much work is required to turn the dial if friction is neglected?