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Physics · PYQ NEET UG 2024
हिन्दीGiven below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: The potential \( (V) \) at any axial point, at 2 m distance \( (r) \) from the centre of the dipole of dipole moment vector \( \vec{P} \) of magnitude, \( 4 \times 10^{-6} \text{ C m} \), is \( \pm 9 \times 10^3 \text{ V} \). (Take \( \frac{1}{4\pi\varepsilon_0} = 9 \times 10^9 \text{ SI units} \)) Reason R: \( V = \pm \frac{2P}{4\pi\varepsilon_0 r^2} \), where \( r \) is the distance of any axial point, situated at 2 m from the centre of the dipole. In the light of the above statements, choose the correct answer from the options given below:
Correct answer · Option 1
A is true but R is false.
Explanation
Electric potential on the axis of a dipole is \( V = \pm \frac{1}{4\pi\varepsilon_0} \frac{P}{r^2} = \pm 9 \times 10^9 \times \frac{4 \times 10^{-6}}{2^2} = \pm 9 \times 10^3 \text{ V} \). So Assertion A is true. Reason R claims \( V = \pm \frac{2P}{4\pi\varepsilon_0 r^2} \), which is incorrect because the factor of 2 applies to electric field, not potential. Thus, A is true but R is false.
