Question

Two capacitors of $2\mu F$ and $3\mu F$ are charged to $150volt$ and $120volt$ respectively. The plates of capacitor are connected as shown in the figure. A discharged capacitor of capacity $1.5\mu F$ falls to the free ends of the wire. Then :

• A. charge on the $1.5\mu F$ capacitors is $180\mu C$
• B. charge on the $2\mu F$ capacitor is $120\mu C$
• C. positive charge flows through $A$ from right to left
• D. positive charge flows through $A$ from left to right

Answer 1

Answer: (A), (B), (C)

charge on the $1.5\mu F$ capacitors is $180\mu C$
charge on the $2\mu F$ capacitor is $120\mu C$
positive charge flows through $A$ from right to left

Charge in $2\mu F$ Capacitor $=300\mu C$

Charge in $3\mu F$ Capacitor $=360\mu C$

when $1.5\mu F$ falls on the circuit ends, Re-distribution of charge now will be:

Charge in $2\mu F$ Capacitor $=300-x\mu C$

Charge in $3\mu F$ Capacitor $=360-x\mu C$

Charge in $1.5\mu F$ Capacitor $=x\mu C$

By Kirchoff Voltage Law:

$\frac{x}{1.5}=\frac{300-x}{2}+\frac{360-x}{3}$

which gives $x=180\mu C$

Therefore Answers are A, B & C