CBSE Class 12 Physics 2023 Delhi Set 3 Paper

Question : 10 of 14

Marks: +1, -0

Three points charges

Q, q

and

-q

are kept at the vertices of an equilateral triangle of side

L

as shown in figure. What is

(i) theelectrostatic potential energy of the arrangement? and
(ii) the potential at point

D

Solution:

Potential energy of the system

=U=\;{1}/{4 π ε_0}

[\;{(+q)(-q)}/{L}+\;{(+q) Q}/{L}+\;{(-q) {\Q}}/{L}]

=\;{-1}/{4 π ε_0} \;{q^2}/{L}

Potential at D:

Distance from

{\Q}

{\D}=\;{{√{3}}}/{2} L

V_D\;=K [\;{Q}/{{{√{3}} L}/{2}}+\;{-q}/{{L}/{2}}+\;{+q}/{{L}/{2}}]

\;=\;{2 K Q}/{{√{3}} L}

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