1. Electric Charges and Fields
normal

Two point charges $+q$ and $-q$ are held fixed at $(-d, 0)$ and $(d, 0)$ respectively of a $x -y$ coordinate system. Then

A

the electric field $E$ at all points on the axis has the same direction

B

work has to be done in bringing a test charge from $\infty $ to the orgin

C

electric field at all points on $y-$ axis is along $x-$ axis

D

the dipole moment is $2qd$ along the $x-$ axis

Solution

If we take a point $M$ on the $X-$ axis as shown in the figure, then the net electric field is in $X-$ direction.

$\therefore $ Option $(a)$ is incorrect.

If we take a point $N$ on $Y-$ axis, we find net electric field along $+X$ direction. The same will be true for any point on $Y-$ axis. $(c)$ is a correct option.

${W_{ \propto 0}} = q({V_ \propto } – {V_0}) = q(0 – 0) = 0$

$\therefore $ $(b)$ is incorrect. The direction of dipole moment is from $-ve$ to $+ve$. Therefore $(d)$ is incorrect.

Standard 12
Physics

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