Question

The capacitance of an air capacitor is `15 muF` te separation between the parallel plates is `6 mm`. A copper plate of `3 mm` thickness is introduced symmetrically between the plates. The capacitance now becomes
A. `5 muF`
B. `7.5 muF`
C. `22.5 muF`
D. `30 muF`

Answer 1

Correct Answer - D
By using `C_(air) = (epsilon_(0)A)/(d), C_(medium) = (epsilon_(0)A)/(d - t+(t)/(K))`
For `K = oo C_(medium) = (epsilon_(0)A)/(d - t)`
`rArr (C_(m))/(C_(a)) = (d)/(d - t) rArr (C_(m))/(15) = (6)/(6 - 3) rArr C_(m) = 30 muC`