## Why does the apparent resistivity depends on the electrode configuration used?

The apparent resistivity is affected by material at increasingly greater depths (hence larger volume) as the electrode spacing is increased. Because of this effect, a plot of apparent resistivity against electrode spacing can be used to indicate vertical variations in resistivity.

**What are the three electrode arrays used in electrical resistivity survey?**

The electrical resistivity method was used to infer the subsurface soil layer by use of three types of arrays, namely, the pole–dipole, Wenner, and Schlumberger arrays.

**What are the methods of electrode configuration in electrical resistivity survey?**

The three main methods of electric resistivity surveys are vertical electric sounding (VES), electric profiling, and electric imaging. Each of these utilize one of the array configurations mentioned above.

### What is the difference between resistivity and apparent resistivity?

Apparent resistivity is equal the earth’s true resistivity only when the earth is a uniform halfspace. When the earth is more complicated, the measured apparent resistivity will lie between the maximum and the minimum of the true resistivities.

**What are the types of electrode configuration?**

Usual configurations comprise two current electrodes and two potential electrodes whose separations are known and defined by a geometric factor. Common configurations include the dipole–dipole, Schlumberger, square, and Wenner arrays.

**What is the geometric factor for Schlumberger array?**

The geometric factor for the three main electrode configurations are: dipole–dipole, Kg = πn(n + 1)(n + 2)p; Schlumberger, Kg = (πp2/q)(1 – q2/4p2); Wenner, Kg = 2πp, where p and q are defined for each case.

#### What is the relationship among V i and r?

The relationship between voltage, current, and resistance is described by Ohm’s law. This equation, i = v/r, tells us that the current, i, flowing through a circuit is directly proportional to the voltage, v, and inversely proportional to the resistance, r.

**How does the size of the electrode array affect resistivity?**

To investigate changes in resistivity with depth, the size of the electrode array is varied. The apparent resistivity is affected by material at increasingly greater depths (hence larger volume) as the electrode spacing is increased.

**What is an electrode array?**

An electrode array is a configuration of electrodes used for measuring either an electric current or voltage. Some electrode arrays can operate in a bidirectional fashion, in that they can also be used to provide a stimulating pattern of electric current or voltage.

## What are the different methods of measuring resistivity?

Resistivity Methods 1 Apparent Resistivity. Wherever these measurements are made over a real heterogeneous earth, as distinguished from the fictitious homogeneous half-space, the symbol ρ is replaced by ρa for apparent resistivity. 2 Schlumberger Array. 3 Wenner Array. 4 Dipole-dipole Array. 5 Depth of Investigation.

**What determines the minimum and maximum spacings of an electrode array?**

For either type of electrode array, minimum and maximum spacings are governed by the need to define the asymptotic phases of the apparent resistivity curve and the needed depth of investigation.