The current in the primary circuit of a potentiometer wire is 0.5 A. Specific resistance of wire is `4 xx 10^(-7) Omega` m and area of cross section of wire is `8 xx 10^(-6) m^(2)`. The potential gradient on the wire would be

Options

A. 2.5 m V/m
B. 25 mV/m
C. 25 V/m
D. 10 V/m

Answer

B

Explanation

25 mV/m
Potential gradient `sigma = (I rho)/(A) = (0.5 xx 4 xx 10^(-7))/(8 xx 10^(-6))`
`therefore sigma = 0.25 xx 10^(-1) = 25 xx 10^(-3)`
`therefore sigma = 25 ` m V/m