The minimum value of effective capacitance that can be obtained by combining 3 capacitors of capacitances 1 pF, 2 pF and 4 pF is

Options

A. `(7)/(4)pF`
B. `(4)/(7)pF`
C. 1 pF
D. 2pF

Answer

B

Explanation

`C_(1) = 1 pF, C_(2) = 2 pF` and `C_(3) = 4 pF`
The combined capacitance is least when all the capacitors are connected in series combination. The effective capacitance C will be,
`(1)/(C)= 1+ (1)/(2)+ (1)/(4)= (7)/(4)` or `C'= (4)/(7)pF`