A current of 0.01 mA passes through the potentiometer wire of a resistivity of `10^(9)Omega` cm and area of cross-section `10^(-1) cm^(-2)` . The potential gradient is

Options

A. `10^(9) V/m`
B. `10^(11) V/m`
C. `10^(10) V/m`
D. `10^(8) V/m`

Answer

D

Explanation

Potential gradient is given by
`k=(V)/(l)=(lR)/(l) " " (because V = lR)`
`= (l xx rho l// A)/(l) " " (because R = (rho l)/(A))`
`therefore k = (0.01xx10^(-3)xx10^(9)xx10^(-2))/(10^(-2)xx10^(_4))=10^(8) V//m`