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Electrostatics

Section: Physics

Question : 43 of 59

Marks: +1, -0

If the electric field due to a point charge varies as $r^{-2.5}$ instead of $r^{-1}$ , then the Gauss law will still be valid.
The Gauss law can be used to calculate the field distribution around an electric dipole.
If the electric field between two point charges is zero somewhere, then the sign of the two charges is the same.
The work done by the external force in moving a unit positive charge from point A at potential $V_A$ to point B at potential $V_B$ is $(V_B - V_A)$ .

Solution:

• According to Gauss’s law:

\oint \vec{E} \cdot \vec{dA}

\frac{q_{\text{in}}}{\varepsilon_0}

that is, it is constant with respect to a distance from a point charge. That is, the electric flux from a point charge is directly proportional to

\frac{1}{\sqrt{r}}

(in new conditions and which is not constant). Hence, option (A) is not correct.

• Gauss’s law is for finding the flux, but not used for finding the field the distribution. Hence, option (B) is not correct.

• If there are two charges, then option (C) is correct.

• The work done by electrostatic force to move a point charge from

V_A

V_B

V_B - V_A

. Hence, option (D) is correct.

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