The plates of a parallel plate capacitor are charged up to 200 V. A dielectric slab of thickness 4 mm is inserted between its plates. Then, to maintain the same potential difference between the plates of the capacitor, the distance between the plates increased by 3.2 mm. The dielectric constant of the dielectric slab is

Options

A. 1
B. 4
C. 5
D. 6

Answer

( c)

Explanation

`C_(0)= C`
`epsilon_(0)A/d = epsilon_(0)A/d' - t +t/k`
`rArr d' - d = t - 1/k `
`rArr d' - d = t(1 - 1/k)`
`rArr 3.2 = 4(1 - 1/k)`
`rArr 4k = 5k - 5`
`:. ` k = 5