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

Answer

B

Explanation

`C_(S)=(1xx4)/(1+4)=(4)/(5)muF`
As A and B are connected in series,
Charge `q=C_(S)xxV=(4)/(5)muFxx35=28muC`
When a medium of dielectric constant K=3 is introduced between the plates of A, its capacity becomes `3C_(1)=3muF` since A and B are joined in eries, their resultant capacity is given by `C_(S)'=(3xx4)/(3+4)=(12)/(7)muF` and the charge q' on ,
them will be `q'=C_(S)'V=(12)/(7)xx35=60muC`
`therefore`Change in the chage on the combined capacitor
`=60-28=32muC`