Question

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

• `4/7  "pF"`

• 1 pF

• 2 pF

• `7/4  "pF"`

Answer 1

The minimum value of effective capacitance that can be obtained by combining 3 capacitors of capacitances 1 pF, 2 pF and 4 pF is `4/7  "pF"`.

Explanation:

Effective capacitance will be minimum when all three capacitors are connected in series.

`therefore 1/"C"_"s" = 1/"C"_1 + 1/"C"_2 + 1/"C"_3`

`therefore 1/"C"_3 = 1/1 + 1/2 + 1/4`

`therefore "C"_"s" = 4/7  "pF"`