A `4 muF` condenser is connected in parallel to another condenser of `8 muF`. Both the condensers are then connected in series with a `12 muF` condenser and charged to `20` volts. The charge on the plate of `4muF` condenser is

Options

A. `3.3 muC`
B. `40 muC`
C. `80 muC`
D. `240 muC`

Answer

B

Explanation

Equivalent capacitance of the circuit `C_(eq) = 6 muF`
Charge supplied from source `Q = 6 xx 20 = 120 muC`
Hence charge on the plates of `4 muF` capacitor
`Q' = (4)/((4 + 8)) xx120 = 40 muC`