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Conductivity

The ability to pass electrical charge by water is measured by conductivity. Conductivity thus is possible only if the water has dissolved inorganic salts in it which facilitates the exchange of ions across the medium. The dissolved anions (negative charged ions) and cations (positive charged ions) help in carrying the charges to their respective electrodes. 

Temperature plays a big role as well in conductivity as warmer the water temperature better the conduction. Organic substances do not conduct electrical charges as there are no free ions to carry these ions.

Related Calculators
Thermal Conductivity Calculator
 

Water Conductivity

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Water being a mixture of many substances dissolved in it which includes minerals, metals and salts helps in conduction as it plays the role of a solvent while the rest as solutes. The combination of both makes the solution.

The solutes create ions which are nothing but atoms which are charged and help in moving the electricity through water. The water conductivity measure is thus a good way of gauging how pure a water sample could be as the more solutes are dissolved in, the better and faster the electric charges move through it.

Conductivity of Water

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The conductivity will respond to only ionic compounds of the solution. The conductivity is thus a strong function of the composition of the waters. The conductance of sea water in dilute solutions is larger than the values of rivers as the conductance of Na+ and Cl- are larger than other salts of Mg2+, Ca2+ or HCO3- which are major components of rivers.

The conductivity measurements at 25oC on the waters collected from the lake and sea water shows that conductance depends on free ions available in water. More the number of free ions in water the faster the conductance in water.

Thermal Conductivity

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The thermal conductivity measurement was used a perfect tool for all kinds of lattice defect investigation as well as to detect the defects or imperfections in solids. In addition to this there is opportunity to investigate exciting and path breaking physical phenomenon as well as other technological advances. The conductivity of materials with both extremes of high and low thermal conduction is technologically intriguing and important to prepare greater combinations of alloys and precision instruments like thermostats as well as chipsets.

High thermal conductivity materials like diamonds or silicon are studies extensively as they are potentially important for applying electronics management in thermal conductions, low thermal conducting material like skutterudites and clathrates. Thermal energy could be transmitted through solids by using electrical carriers like electrons, lattice waves, electromagnetic waves, spin waves or any other excitations. In any metals electrical carriers would carry the majority of the heat while the insulators lattice waves are the dominant heat transporter.

Hence the total thermal conductivity K could be written as a sum of all the components which represents the various excitations

K = $\sum_{\alpha} K_{\alpha}$
 
Where, $\alpha$ denotes excitations.

The thermal conductivities of solids might vary in magnitude and temperature but this might depend from one material to another. These are caused by differences in sample sizes for single crystals or grain sizes for all kinds of polycrystalline samples, lattice defects or imperfections, or dislocations.

The great variety of process makes the thermal conductivity a very interesting is of theoretical as well as experimental study.

Electrical Conductivity

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The electrical conductivity of substances is usually defined as the reciprocal of electrical resistivity and this resistivity of a section of the substance 1 cm2 in cross section and one cm long. The units of electrical resistivity are ohm cm and hence the units of electrical conductivity are ohm-1 cm-1.

The atomic conductance is the conductivity of a block of a substance 1 cm2 in cross section but long enough to contain one mole of atoms of the element.

Categories of conductivity
  • Metals are good conductor of electricity with atomic conductance greater than 10-3 ohm-1 cm-4. This conductivity fall slowly as the temperature rises.
  • Metalloids are considered to be poor conductors of electricity with atomic conductance usually lower than 10-3 and at the same time more than 10-5 cm-4. The metalloid conductivity increases as the temperature rises and is also considerably get affected due to impurity present in these.
  • Non-metals are non-conductors or insulators and their atomic conductance is usually less than 10-10 ohm-1 cm-4

Conductivity Meter

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For any electrolytic conductivity meters with the function to display the conductance cell constant. For electrolytic conductivity meters without function of displaying conductance cell’s constant the standard conductivity Gso is selected which is equal to or close to the upper limit value of the being verified range as the input.

The corresponding standard conductivity Ka = KcellR Gs

The electrolytic conductivity meter measurement value KM is followed before calculating the electric unit.

For any electrolytic conductivity meter without constant adjustment function or the constant is not displayed then it is exempted from calculation.

$\frac{\Delta K}{K_{F}}$ = $\frac{K_{M} - K_{a}}{K_{F}}$ X 100 %
 
For any conductivity value if the meter is not giving proper reading, the batteries, proper calibration solution or fresh calibration solution needs to be checked.

Conductivity Units

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Various units are used in thermal properties but before SI system the common units for thermal conductivity used were
$\frac{Cal}{cm^o c}$ and the $\frac{BTU in}{ft^{2} h^{o} F}$

The SI unit for conductivity is $\frac{W}{m k}$ while the unit for diffusivity is the $\frac{M^{2}}{s}$
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