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The electric potential at a distance ______ due to the charge 4×10⁻⁷ C is 4×10⁴ V.

Asked in GSEB Board March 2022 · Potential of point charges

• (1) 9 cm
• (2) 9 mm
• (3) 9 μm
• (4) 9 m

Step-by-step solution

Why the other options are wrong

• (2) r = 0.09 m = 9×10⁻² m, which is 9 cm; 9 mm is 9×10⁻³ m, a centi-milli mix-up. At 9 mm the potential would be 4×10⁵ V.
• (3) No single slip gives 9 μm. Sanity check: at 9×10⁻⁶ m, V = (kq)/r = 4×10⁸ V, ten thousand times too large.
• (4) No single slip gives 9 m. Sanity check: at 9 m, V = (kq)/r = (3600)/9 = 400 V, not 4×10⁴ V.

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