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# Two identical metallic spherical shells A and B having charges $+4\; Q$ and $10\; Q$ are kept a certain distance apart. A third identical uncharged sphere C is first placed in contact with sphere A and then with sphere B, then spheres A and B are brought in contact and then separated. Find the charge on the spheres A and B.

$\begin{array}{1 1}(A)\;Q \\(B)\;-Q\\(C)\;2Q \\(D)\;0 \end{array}$

When C and A are placed in contact, charge of A equally divides in two spheres.
Therefore charge on each A and $C = +2Q$
Now, C is placed in contact with B, then charge on each B and becomes
$\qquad=\large\frac{2Q+(-10Q0)}{2}$$=-4Q When A and B are placed in contact then charge on each A and B becomes \qquad=\large\frac{2Q+(-4Q)}{2}$$=-Q$
Hence B is the correct answer .