[Physics Class Notes] on Conductivity of Water Pdf for Exam

Conductivity is inversely proportional to resistance. This is the property of a metal to conduct current when voltage i.e, potential difference is passed through it. Here, resistance is measured in ohms whereas conductivity in mhos. As such, ohm becomes mho because of the applied condition.

 

What is Conductivity?

Electric metals and solutions of ionic salts in water are good conductors. Even though the human body has high resistance, it still conducts electricity, so we get electric shock.

Simply, the Ohm’s law can define Conductivity as:

V=IR

Where,

R is resistance,

I is current and

V is voltage present in a material

From the above formula, conductivity depends on the number of charge carriers (electrons) in the material and their mobility. In metal, it is assumed that all outer electrons are free to carry charge. Further, impedance for flow of charge is mainly due to electrons bumping each other. Hence, for metal, as the temperature increases, the resistance of the material increases. Here, electrons bump into each other more as they move faster.

 

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Insulators are tightly bound electrons so that nearly no electrons flow occurs; as a result, they offer a high resistance to charge flow. Free electrons are required for conductance.

The below diagram shows how conductivity of conjugated polymers like polyacetylene can vary from being an insulator to a conductor:

 

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Conductivity Formula

The formula for conductivity is the inverse of the resistivity that is:

σ=1/ρ​

Here

σ = refers to electrical conductivity

ρ = refers to resistivity

 

Water Conductivity Units

The ability of the substance to conduct or transmit heat, electricity, or sound is known as conductivity. Its SI unit is Siemens per meter

S/m

S/m, U.S customary unit is milliohms per centimeter

mmho/cm, and is denoted by k or s.

Siemens per meter (S.m−1) is conductivity unt. It is also referred to as mho- that is reciprocal of Ohm, and this is incidental by spelling Ohm backwards.

Also, conductance is reciprocal of resistance, and one Siemens is equivalent to reciprocal of one Ohm.

 

Conductivity of Water

The measurement of the ability of water to pass electrical flow through it is known as conductivity of water. It directly depends on the concentration of conductive ions present in water. The sources of origin for conductive ions are the inorganic material, such as chloride, carbonate, alkalis and sulfide compounds and dissolved salts.

Conductivity of water is also known as the degree to which water conducts or transmits electricity or heat or sound in it, and is denoted by s or k.

Multiple units can be used to measure the conductivity of water, some of which are mentioned below.

 

Units

 

Conductance and Conductivity

1. Conductance

One must first understand the resistance of an object to understand conductance. Resistance is an elemental property that works in areas of electronics & electricity.. The resistance of a substance tells us how hard it is for an electrical current to flow through it. Also, electrical conductance is considered as a property of the component itself.

2. Conductivity

There are various things upon which the resistance of a component depends like the conductor’s length, area of conductor, and the conductor’s material. The conductivity of a material is reciprocal to resistivity and is denoted by the Greek letter σ. Conductivity is a specific property of the material at a given temperature.

 

Electrical Conductivity of Water

The ability of water to conduct an electric current is known as EC or Electrical conductivity of water. Chemicals or salts break down and dissolve in the water as positive and negative charged ions and these free ions in water conduct electricity. As a result, water electrical conductivity depends upon the concentration of ions. 

To calculate the EC of water salinity and total dissolved solids are used, it helps to indicate the water’s purity. The conductivity is less for purer water. For example, distilled water acts as an insulator, whereas saltwater is a very efficient electrical conductor.

 

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Sodium, potassium, calcium, and magnesium are major positively charged ions that affect the conductivity. Similarly, chloride, carbonate, sulfate, and bicarbonate are major negatively charged ions. 

Whereas, nitrates and phosphates are minor contributors to conductivity, but are important biologically. Rain, geology, and evaporation are natural impacts of EC in water. Human impacts include road salt, septic/landfill leachate, impervious surface runoff, and agricultural runoff.

Water Conductivity’s Importance

A number of measures must be kept to properly ensure that fish and other species in the water remain healthy. Water conductivity, which refers to the degree to which water can carry electricity, is one of these measures. How well electricity can travel through water determines the conductivity of electricity in the water. If you try to carry electricity through pure water, you will not be able to since pure water contains very few ions. Water conductivity is increased when there are large numbers of ions present.

Water conductivity is important for a variety of reasons. In fact, while attempting to determine the quality of water, it is one of the most typical measurements done. In most cases, conductivity measurements are used to calculate total dissolved solids and salinity in water. Conductivity measurements are done on a regular basis in many bodies of water to ensure that the water quality is maintained and that the plants and animals in the water are not harmed. When conducting conductivity measurements on a regular basis, the results should be generally constant. However, once excessive levels of pollution enter the water, evaporation happens, or natural floods occur, these measurements may fluctuate significantly. These occurrences can have a significant impact on the overall water quality.