JEE MAIN - Physics (2019 - 11th January Morning Slot - No. 13)
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 :
_11th_January_Morning_Slot_en_13_1.png)
$${{ - q} \over {1 + \sqrt 2 }}$$
+ q
$$-$$ 2q
$${{ - \sqrt 2 q} \over {\sqrt 2 + 1}}$$
Explanation
_11th_January_Morning_Slot_en_13_2.png)
U = K$$\left[ {{{{q^2}} \over a} + {{Qq} \over a} + {{Qq} \over {a\sqrt 2 }}} \right] = 0$$
$$ \Rightarrow $$ q = $$-$$ Q$$\left[ {1 + {1 \over {\sqrt 2 }}} \right]$$
$$ \Rightarrow $$ Q = $${{ - q\sqrt 2 } \over {\sqrt 2 + 1}}$$
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