Question 836: Electrostatics & Capacitance

Question

The figures below depict two situations in which two infinitely long static line charges of constant positive line charge density $\lambda $ are kept parallel to each other. In their resulting electric field, point charges $q$ and $-q$ are kept in equilibrium between them. The point charges are confined to move in the $x$ direction only. If they are given a small displacement about their equilibrium positions, then the correct statement(s) is (are)

Accepted Answer

$E = {\lambda  \over {2\pi {\varepsilon _0}r}}$
Case 1 : If q is shifted towards right by x, we get
$F = {F_2} - {F_1} = {{\lambda q} \over {2\pi {\varepsilon _0}}}\left( {{1 \over {{d \over 2} - x}} - {1 \over {{d \over 2} + x}}} \right)$ (towards left)
Case 2 : If $-$q is shifted towards right by x
$F = {F_2} - {F_1} = {{\lambda q} \over {2\pi {\varepsilon _0}}}\left( {{1 \over {{d \over 2} - x}} - {1 \over {{d \over 2} + x}}} \right)$ (towards right)
Thus, +q exhibits SHM while $-$q continues to move towards rightwards.

Answer

Both charges execute simple harmonic motion

Answer

Both charges will continue moving in the direction of their displacement

Answer

Charge $+q$ executes simple harmonic motion while charge  $-q$ continues moving in the direction of its displacement

Answer

Charge $-q$ executes simple harmonic motion while charge $+q$ continues moving in the direction of its displacement

Electrostatics & Capacitance

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