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CBSE Class 12 Physics 2023 Delhi Set 3 Paper

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Question : 10 of 14
Marks: +1, -0
Three points charges Q,qQ, q and −q-q are kept at the vertices of an equilateral triangle of side LL as shown in figure. What is
(i) theelectrostatic potential energy of the arrangement? and
(ii) the potential at point DD ?
Solution:     👈: Video Solution
Potential energy of the system =U=14πε0=U=\frac{1}{4\pi\varepsilon_0}
[(+q)(−q)L+(+q)QL+(−q)QL]\left[ \frac{(+q)(-q)}{L} + \frac{(+q)Q}{L} + \frac{(-q)Q}{L} \right] =−14πε0q2L=\frac{-1}{4\pi\varepsilon_0}\frac{q^2}{L}
Potential at D:
Distance from QQ to D=32LD=\frac{\sqrt{3}}{2}L
VD=K[Q3L2+−qL2++qL2]V_D=K\left[ \frac{Q}{\frac{\sqrt{3}L}{2}} + \frac{-q}{\frac{L}{2}} + \frac{+q}{\frac{L}{2}} \right]
=2KQ3L=\frac{2KQ}{\sqrt{3}L}
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