Electrostatics 7 Question 14

14. Two point charges +q and q are held fixed at (d,0) and (d,0) respectively of a xy co-ordinate system. Then

(1995, 2M)

(a) the electric field E at all points on the x-axis has the same direction.

(b) work has to be done in bringing a test charge from to the origin.

(c) electric field at all point on y-axis is along x-axis.

(d) the dipole moment is 2qd along the x-axis.

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Answer:

Correct Answer: 14. (c)

Solution:

  1. The diagramatic representation of the given question is shown in figure.

The electrical field E at all points on the x-axis will not have the same direction.

For dxd, electric field is along positive x-axis while for all other points it is along negative x-axis.

The electric field E at all points on the y-axis will be parallel to the x-axis (i.e. i^ )

[option (c)]

The electrical potential at the origin due to both the charges is zero, hence, no work is done in bringing a test charge from infinity to the origin.

Dipole moment is directed from the q charge to the +q charge (i.e. i^ direction).



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