Two air capacitors A and B having capacities 1 `muF` and `4muF` respectively are connected in series with a 35 V source. A medium of dielectric constant K=3 is introduced in between the plates of A. what is the change in the charge on the combined capacitor?

Options

A. `32 mu C`
B. `16 muC`
C. `60 muC`
D. `28 muC`

Answer

A

Explanation

`(1)/(C_(s)) = (1)/(1) + (1)/(4) = (5)/(4)` or `C_(s) = (4)/(5) mu F`
`q = C_(s) xx V = (4)/(5) mu F xx 35 V = 28 mu C`
When a medium of dielectric constant K = 3 is introduced in A, its capacity becomes `1 xx 3 mu F`
`:. (1)/(C._(s)) = (1)/(3) + (1)/(4) = (7)/(12)` or `C._(s) = (12)/(7) mu F`
`q. = C._(s) xx V = (12)/(7) mu F xx 35 V = 60 mu C`
`q. - q = 60 mu C - 28 mu C = 32 mu C`