The conducting plates of a parallel plate capacitor are separated by 2 cm from each other. A dielectric slab (k =5) of thickness 1 cm is inserted between the two plates. The distance between the plates is now so changed that the capacitance of the capacitor remains the same. What will be the new distance between the plates?

Explanation

Let the present distance between the plates be d. According to the question,
`(in_0 alpha)/(2)= (in_0 alpha)/([d-t+(t)/(k)]) [t = " thickness of the dielectric slab " = 1 cm, k=5]`
or `(1)/(2)= (1)/([d-1+(1)/(5)])" or "2 = [d-1+(1)/(5)] = d-(4)/(5)`
or `d= (14)/(5) = 2.8` cm