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The value of electric potential at a distance of 9 cm from the point charge 4×10⁻⁷ C is [Given 1/(4πε₀)=9×10⁹ N m² C⁻²]:

Asked in Re-NEET 2024 · Potential of point charges

(1) 4×10² V
(2) 44.4 V
(3) 4.4×10⁵ V
(4) 4×10⁴ V

Answer: (4) 4×10⁴ V

Step-by-step solution

V=(kq)/r=(9×10⁹×4×10⁻⁷)/(9×10⁻²).

V=4×10⁴ V.

Why the other options are wrong

(1) Two powers of ten low: takes the distance as 9 m instead of 0.09 m.
(2) No single slip gives 44.4 V; it is about 900 times too small.
(3) No single slip gives 4.4×10⁵ V; the 9 in k and the 9 cm cancel exactly, leaving 4×10⁴ V.

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