Current Electricity - Result Question 107

112. If specific resistance of a potentiometer wire is $10^{-7} \Omega m$, the current flow through it is $0.1 A$ and the cross-sectional area of wire is $10^{-6} m^{2}$ then potential gradient will be

[2001]

(a) $10^{-2}$ volt $/ m$

(b) $10^{-4} volt / m$

(c) $10^{-6} volt / m$

(d) $10^{-8}$ volt $/ m$

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Answer:

Correct Answer: 112. (a)

Solution:

  1. (a) Potential gradient $=$ Potential fall per unit length.

In this case resistance of unit length.

$R=\frac{\rho l}{A}=\frac{10^{-7} \times 1}{10^{-6}}=10^{-1} \Omega$

Potential fall across $R$ is

$V=I . R=0.1 \times 10^{-1}=0.01 volt / m$.

$=10^{-2}$ volt $/ m$