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If specific resistance of a potentiometer wire is 10⁻⁷ Ω m and current flow through it is 0.1 A, cross-sectional area of wire is 10⁻⁶ m² then potential gradient will be

Asked in CBSE AIPMT 2001 · Potentiometer

• (1) 10⁻² V/m
• (2) 10⁻⁴ V/m
• (3) 10⁻⁶ V/m
• (4) 10⁻⁸ V/m

Step-by-step solution

Why the other options are wrong

• (2) No single slip gives 10⁻⁴ V/m; it is a hundred times below ρ I/A.
• (3) No single slip gives 10⁻⁶ V/m; it is just the area's own power of ten, not a gradient.
• (4) Is ρ I alone; the division by the area 10⁻⁶ m² has been left out.

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