JEE MAIN - Physics (2019 - 9th April Morning Slot - No. 21)

A system of three charges are placed as shown in the figure :

JEE Main 2019 (Online) 9th April Morning Slot Physics - Electrostatics Question 171 English If D >> d, the potential energy of the system is best given by :
$${1 \over {4\pi {\varepsilon _0}}}\left[ { {{{q^2}} \over d} + {{qQd} \over {{D^2}}}} \right]$$
$${1 \over {4\pi {\varepsilon _0}}}\left[ { - {{{q^2}} \over d} - {{qQd} \over {2{D^2}}}} \right]$$
$${1 \over {4\pi {\varepsilon _0}}}\left[ { - {{{q^2}} \over d} - {{qQd} \over {{D^2}}}} \right]$$
$${1 \over {4\pi {\varepsilon _0}}}\left[ { - {{{q^2}} \over d} + {2{qQd} \over {{D^2}}}} \right]$$

Explanation

Utotal = Uself of dipole + Uinteraction

= $$ - {{k{q^2}} \over d} - \left( {{{kQ} \over {{D^2}}}} \right)qd$$

$$ = - k\left[ {{{{q^2}} \over d} + {{qQd} \over {{D^2}}}} \right]$$

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