Question

The middle plate is given a charge $+Q$, Switch $S_1$ and $S_2$ are initially open, and the first and third plates are initially charge neutral. Now after closing the switch $S_1$ and $S_2$ remains open, find out the final charge on the left side of the middle plate.

• A. $-Q/2$
• B. $0$
• C. $+Q$
• D. $+Q/2$

Answer 1

The correct option is C $+Q$

After closing the switch, charge on outers surface of the left plate will become zero. According to Gauss law, charge on outer plate of rightmost plate will also become zero. Since rightmost plate is not connected to ground and initially it was uncharged, so charge on inner surface of this plate will also become zero. Total charge of the middle plate will appear on its left surface.

So, charge on the left side of the middle plate is $+Q$.