JEE Advance - Physics (2011 - Paper 2 Offline - No. 1)
Which of the following statement(s) is/are correct?
If the electric field due to a point charge varies as $${r^{ - 2.5}}$$ instead of $${r^{ - 2}},$$ 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 $$\left( {{V_B} - {V_A}} \right).$$
설명
Gauss's law is valid only if Coulomb's law holds, i.e. if $$E \propto {r^{ - 2}}$$. Hence, choice (a) is wrong. Gauss's law cannot be used to calculate a non-uniform field distribution around an electric dipole. So choice (b) is also wrong.
Choice (c) is correct because the directions of electric fields are opposite at a point between two similar charges.
Work done $${W_{A \to B}} = q({V_B} - {V_A}) = ({V_B} - {V_A})$$ ($$\because$$ $$q = + \,1\,C$$)
Hence, choice (d) is correct.
So the correct choices are (c) and (d).