Question

Five identical plates are connected across a battery as shown. If the charge on plate 1 be +q, then the charges on the plates 2, 3, 4 and 5 are:

• A. $-q,+q,-q,+q$
• B. $-2q,+2q,-2q,+q$
• C. $-q,+2q,-2q,+q$
• D. $noneoftheabove$

Answer 1

The correct option is B $-2q,+2q,-2q,+q$

As the plate 2 is common plate for two capacitors and connected to the negative terminal of battery so its charge should be $-(q+q)=-2q$.
Similarly plate 3 is also common plate between two capacitors and connected to the positive terminal of battery so its charge should be $+(q+q)=+2q$.
Similarly for plate 4, charge on it $=-(q+q)=-2q$
Plate 5 is not common plate between two capacitors and connected to positive end of battery. Thus its charge $=+q$