Question

The resistivity of a potentiometer wire is 40 × 10^–8Ωm and its area of cross section is 8 × 10^–6m². If 0.2 amp. Current is flowing through the wire, the potential gradient will be

• A. 10^–2volt/m
• B. 10^–1volt/m
• C. 3.2 × 10^–2volt/m
• D. 1 volt/m

Answer 1

Answer: (A)

10^–2volt/m

Answer 2

Potential gradient $= \frac{V}{L} = \frac{iR}{L} = \frac{i\rho L}{AL} = \frac{i\rho}{A}$

$= \frac{0.2 \times 40 \times 10^{- 8}}{8 \times 10^{- 6}} = 10^{- 2}V ⥂ /m$