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

CSIR-NET 2014

105. If an electric field of strength 100 mV/km is injected in the ground and the strength of the recorded magnetic field is 1500 gamma, the corresponding apparent resistivity at time period 1000s , is

a) 0.9 ohm m

b) 15ohm m

c) 100 ohm m

d) 5 ohm m

Solution:

Electrical field strength = 100 mV/km

magnetic field = 1500 gamma

time period = 1000 s

The relation between the apparent resistivity, electrical field, magnetic field and time period is

ρ_a = 0.2 *T *(|E/H|)² ---------------------------(1)

ρ_a =(0.2 * 1000 (|100/1500|)² )

ρ_a = 0.88 Ωm

Therefore, apparent resistivity ρa= 0.9 Ωm