Electrostatics Question 782
Question: Three identical metallic uncharged spheres A, B and C each of radius a, are kept at the corners of an equilateral triangle of side d(d»a) as shown in Fig. The fourth sphere (of radius a), which has a charge q, touches A and is then removed to a position far away. B is earthed and then the earth connection is removed. C is then earthed. The charge on C is
Options:
A) $ \frac{qa}{2d}( \frac{2d-a}{2d} ) $
B) $ \frac{qa}{2d}( \frac{2d-a}{d} ) $
C) $ -\frac{qa}{2d}( \frac{d-a}{d} ) $
D) $ -\frac{2qa}{d}( \frac{d-a}{2d} ) $
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Answer:
Correct Answer: C
Solution:
[c] $ \frac{kq _{1}}{a}+\frac{kq}{2d}=0 $
$ \text{or }q _{1}=\frac{-qa}{2d} $
$ \frac{kq _{1}}{a}+\frac{kq}{2d}+\frac{kq _{1}}{d}=0 $
$ \text{or }q _{2}=\frac{-qa}{2d}( \frac{d-a}{d} ) $
BETA
