Separation between the plates of parallel plate capacitor is 5 mm. this capacitor, having air as the dielectric medium between the plates, is charged to a potential difference 25 V using a battery. The battery is then disconnected and a dielectric slab of thickness 3mm and dielectric constant K=10 is placed between the plates as shown. potential difference between the plates after the dielectric slab has been introduced is-

Options

A. 18.5 V
B. 13.5 V
C. 11. 5 V
D. 6.5 V

Answer

C

Explanation

As the charge remain constant, hence
`Q = CV = C_(1) V_(1)`
`Q = (epsilon_(0) A)/(d ) V = (epsilonA)/( d- t+ (t)/(K ) ) V_(1)`
`(epsilon_(0)A)/(0.005 ) (25 ) = (epsilon_(0)A)/(0.002+(0.003)/(10))(V)`
V = 11.5 V