GATE-2018 (24) :Wyllie – Time average equation

GATE-2016

17. A wenner array with 60m spacing between current electrodes is placed over an in homogeneous  ground. If the measured potential difference and current flow in subsurface are 10mV and 5mA, respectively, the apparent resistivity will be......ohm m

Solution;

In wenner configuration the current and potential electrode pairs have a common mid-point and the distance between adjacent electrodes are equal.

Apparent resistivity (ρ_a) = 2*Π*a (ΔV/ I) -----------------(1)

Total Electrode spacing 3a = 60 m

a= 20 m

a- electrode spacing

ΔV= voltage = 10 mV

I = current = 5 mA

substitute above values in eq(1)

ρ_a = 2* 3.14* 20* (10/ 5)

     = 251.2 Ωm