| Three charges \[Q,+q\]and \[+q\] are placed at the vertices of a right-angle isosceles triangle as shown below. The net electrostatic energy of the configuration is zero, if the value of Q is- [JEE Main 11-Jan-2019 Morning] |
 |
A) \[+q\]
B) \[-2q\]
C) \[\frac{-\sqrt{2}q}{\sqrt{2}+1}\]
D) \[\frac{-q}{1+\sqrt{2}}\]
Correct Answer: C
Solution :
| [c] Let a be the length of two equal sides of the triangle. |
| The net electrostatic energy of the system Is zero |
| \[k\left( \frac{Qq}{a}=\frac{{{q}^{2}}}{a}+\frac{Qq}{\sqrt{2}a} \right)=0\]\[\Rightarrow \]\[Q=-\frac{\sqrt{2}}{\sqrt{2}+1}q\] |
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