Why DC current Cannot be used in conductivity measurements?

All conductance measurements are done by alternating current (AC) and not by direct current (DC). If DC is used, electrolysis will occur and concentration of the solution will change with time. A a result, the observed conductance will be erroneous.

Why DC is not used in conductivity cell?

If you apply DC voltage to the cell the positive ions will be attracted to the negative plate and the negative ions to the positive plate. This will cause the composition of the electrolyte to change while measurements are being made. Application of AC voltage to the plates will prevent this from happening.

How is DC conductivity measured?

Calculate the electrical conductivity from the resistance, length and area of the current. The resistivity is given as p = RA/l where p is the resistivity, R is the resistance, A is the area and l is the length. The conductivity is s = 1/p where s is the conductivity.

Why is AC current used instead of DC in measuring the electrolytic conductance?

Using DC causes polarisation of the electrodes and electrolyte which leads to error in measured conductance values over a period of time. In AC there is no polarisation due to non-continuous flow of current, hence,AC is used.

Why we can use KCL solution for determination of cell constant?

Hello, It is generally limited to the measurement of ultrapure water, the conductivity of which is very low. Determination of the cell constant required to convert conductance readings into conductivity results.

Why is AC used in conductivity meter?

Since conductivity is an indicator of how easily current passes through a solution, it is dependent on the quantity of ions and their mobility in that solution. To prevent this, an alternating voltage (AC voltage) is applied when measuring conductivity, commercial power sources of 50 Hz or 60 Hz usually being used.

Can you measure conductivity?

Conductivity is measured with a probe and a meter. Voltage is applied between two electrodes in a probe immersed in the sample water. Conductivity can be measured in the field or the lab.

Why is AC used for measuring resistance of an electrolytic solution?

Why is alternating current used for measuring resistance of an electrolytic solution? Answer: Alternating current is used in electrolysis so that concentration of ions in the solution remains constant and exact value of resistance is measured.

Why KCl is used for calibration of conductivity meter?

KCl is used for calibration of conductivity meter because it is very stable. KCl or potassium chloride is product of reaction between a strong acid and a strong base, so it is strongly bonded because of high electropositive nature of potassium and high electronegative nature of chlorine.

Which one of the following concentration of KCl is not used for the determination of cell constant?

(d) Saturated solution of KCl cannot be used to determine the value of cell constant.

How to test the conductivity of a DC Circuit?

It may be possible to reverse the polarity of the DC while limiting the amount of time the DC is applied. This will minimize the interference of the current which is occurring outside of the test circuit. This is of course effectively creating an AC test scenario. Look at soil resistivity meters as an example of a good way to test conductivity.

What is the main problem in measuring liquid conductance?

A general problem faced with electrical measurements of liquid conductance is that the derived conductance value ( G) does not tell us much about the liquid itself, because that measurement depends just as much on the geometry of the plates (their area A and separation distance d) as it does on the ionic activity of the liquid solution.

Is it possible to reverse the polarity of the DC current?

In this instance the use of DC will not result in a correct conductivity measurement. It may be possible to reverse the polarity of the DC while limiting the amount of time the DC is applied. This will minimize the interference of the current which is occurring outside of the test circuit.

When is conductivity measurement meaningful?

Therefore, conductivity measurement is meaningful only when we have prior knowledge of the particular ionic species present in the solution (or when the purpose is to eliminate all ions in the solution such as in the case of ultra-pure water treatment, in which case we do not care about types of ions because our ideal goal is zero conductivity).