Four capacitors and a battery are connected as shown in the figure. If the potential difference across the `7 mu F` capacitor is 6 V, then which of the following statement is incorrect ?

Options

A. The potential drop across the `12 muF` capacitor is `10 V`.
B. The charge in the `3 muF` capacitor is `42 muC`.
C. The potential drop across the `3 muF` capacitor is `10 V`
D. The emf of the battery is `30 V`.

Answer

A, B, D

Explanation

Equivalent capacitance of network is `C_(eq)=4 muF`.
.
Charge `Q=C_(eq) V=4 V muC`
The charge on the `7 muF` or `3 muF` capacitor is
`Q_(2)=(7muF)(6 V)=42 muC`
`Q_(2)/(2.1 muF)=Q_(1)/(3.9 muF)` or `Q_(1)=(42 muC)((3.9 muF))/((2.1 muF))=78 muV`
`Q=Q_(1)+Q_(2)=(78 muC+42 muC)=120 muC=4 V muC`
Emf of the battery is `V=30 V`
The potential drop across `12 muF` capacitor is
`Q/(12 muF)=(120 muC)/(12 muF)=10 V`.