Three capacitors each of capacitance 9pF are connected in series.
(a) What is the total capacitance of the combination?
(b) What is the potantial difference across each capacitor if the combination is connected to a 120 V supply?

Explanation

(a) Effective capacitance for the series combination `(C_(s))` of three capacitors of capacitances `C_(1),C_(2) and C_(3)` can be calculated as:
`(1)/(C_(S))=(1)/(C_(1))+(1)/(C_(2))+(1)/(C_(3))`
`(1)/(C_(S))=3xx(1)/(9xx10^(-12))`
`rArr C_(s)=3xx10^(-12)F=3pF`
(b) As all three capacitors are identical, the potential difference across each capacitor will be same, and can be calculated as `(V)/(3)=(120)/(3)V=40V`