Examples of Electrical Conductivity
We explain the examples of electrical conductivity. Why does copper conduct electricity better than water? After reading this tutorial you will surely not ask yourself this question anymore! Next we explain electrical conductivity and we will study, among other things, its formulas and unit of measurement.
What is electrical conductivity? Simple explanation
Conductivity, or electrical conductivity, is in short a quantity of physics that describes how well a given material is capable of conducting electricity. electrical conductivity examples
Examples of Electrical Conductivity
The electrical conductivity is the physical property by which a material is capable of transporting an electrical current through it . It occurs to a greater extent in transition metals and in aqueous solutions of ionic substances, because there are electrons available in them that can help the movement of charges. electrical conductivity examples
Units of conductivity electrical conductivity examples
Electrical conductivity is represented by the Greek letter sigma σ, and is unique for each substance according to its chemical constitution. Units that are handled are the Siemens each meter (S / m). Sometimes the actually measured values are generally very small, so their submultiples are used, such as:
- MicroSiemens / centimeter (mS / cm), which is equal to 1 * 10 -6 Siemens every centimeter.
- MilliSiemens / centimeter (ms / cm), which is equal to 1 * 10 -3 Siemens every centimeter.
Electrical conductivity in substances
All matter that has electrical conductivity is called an electrical conductor . The flow of electrical energy through a conductor is due to the transport of electrons . Depending on how this transport is carried out, this material can be of two types:
- Metallic or electronic conductor
- Ionic or electrolytic conductor
A metallic or electronic conductor is a metal whose internal structure has electrons arranged to transport a charge. The transition metals meet this characteristic, so are suitable: the best conductors are gold, silver and copper. Due to its economy, copper is the most widely used for electrical installations; it is transformed into thin wires and covered with an insulator to make electricity available to humanity.
The ionic or electrolytic conductors are mixtures of water with an ionic compound, ie, aqueous solutions such as salt water table. In them, the conductivity depends directly on the concentration of dissolved solids , therefore, the higher the concentration, the higher the conductivity. If in that case more salt is added to the water, the conductivity of the mixture will be higher. electrical conductivity examples
Conductivity in solutions is also affected by temperature . When the mixture is cold, below room temperature (20 ° C to 25 ° C), the particles are more ordered and the ions will be accessible for the electric current to travel through them. On the other hand, if the solution is hot, its particles will be agitated and will obstruct the flow of the current. It is not only about connecting a source such as a battery, but also regulating the temperature.
How is electrical conductivity measured?
There are specialized devices for measuring electrical conductivity called conductivity meters . The conductivity meters have a sensor, a panel and a digital display that will show the value of conductivity in a substance, especially in aqueous solutions. electrical conductivity examples
- The sensor is tubular in shape and has a membrane at its tip. The latter will come into contact with the aqueous solution and will detect the concentration to relate it to a conductivity value. If several measurements are made, it is always essential to wash the sensor body with distilled water, so that each time it starts from a “blank” and the measurement is authentic.
- The board offers keys for power on, calibration options, change of units (μS / cm to mS / cm), among other more specific commands such as transferring data to a USB memory. electrical conductivity examples
- The digital display will show the conductivity reading in the units that are set before starting. Since it takes time to stabilize the measurement, you will have to wait a few seconds and shake the solution a little so that the membrane assimilates the concentration that is there. The value in the reading will fluctuate until it remains fixed.
Examples of electrical conductivity
- Distilled water: 0.5 μS / cm
- Domestic water: between 500 and 800 μS / cm
- Sea water: 56 mS / cm or 56,000 μS / cm
- Deionized water: 5.5 * 10 -6 S / m
- Maximum value for drinking water: 1,055 mS / cm or 1,055,000 μS / cm.
- Copper: 59.6 * 10 6 S / m
- Graphene: 98.7 * 10 6 S / m
- Silver: 63 * 10 6 S / m
- Gold: 45.5 * 10 6 S / m
- Iron: 15.6 * 10 6 S / m
- Nickel: 14.3 * 10 6 S / m
- Aluminum: 37.8 * 10 6 S / m
- Tungsten: 18.2 * 10 6 S / m
- Palladium: 9.5 * 10 6 S / m
- Zirconium: 2.36 * 10 6 S / m
- Carbon: 2.80 * 10 4 S / m
- Silicon: 1.60 * 10 -5 S / m
- Germanium: 0.0220 S / m
- Quartz: 1.33 * 10 -18 S / m
- Paraffin: 3.37 * 10 -17 S / m
There are three different symbols to represent electrical conductivity: σ (Greek: sigma), K (kappa), and γ (gamma). In this tutorial, we use the Sigma symbol. The formula for electrical conductivity, also called specific conductance , is as follows:
You can calculate the resistance R of a conductor with its parameters with: electrical conductivity examples
Where the resistance R is therefore equal to the specific resistance multiplied by ρ times the length of the conductor l through the cross-sectional area A.
If you now want to express this formula using the specific conductance ( σ ), it is useful to know that the conductance G of a conductor is given by:
If we add the specific conductance σ and the conductance G in the above formula, then the following is obtained:
With a deeper reorganization of the previous formula, the expression is obtained: electrical conductivity examples
Electric current density
With the help of electrical conductivity you can also understand the important relationship between current density and electric field strength with the expression:
The unit in the International System of electrical conductivity σ is:
How was this unit of measure obtained?
This unit is derived from the following formula:
If you solve for sigma from the above formula, you will get
From the conductance G the unit of measurement is:
If you now substitute all the units in the formula you will get
Electrical conductivity of metals
Depending on how many free-moving electrons are available, one material conducts better than another . In principle, any material is conductive, but for example, the current that flows through insulators is negligible, which is why they are called non-conductors. electrical conductivity examples
With metallic bonds, the valence electrons, that is, the outermost electrons of the atom, move freely. These are in the so-called conduction band. electrical conductivity examples
If a voltage is now applied to a metal, the valence electrons move slowly toward the positive pole, because they are attracted to it.
In this formula, n is the number of electrons, e is the charge on the electron, m is the mass of the electron, and τ is the average travel time of an electron between two pulses.
Electrical conductivity table
Electrical conductivities are already determined for most materials. Some of them can be found in the table below.
All values in this table are for ambient temperature, that is, 25 ° C.
|Group||Material||Electrical conductivity σ in S / m|
|Driver||Silver||62 10 6|
|Driver||Copper||58 10 6|
|Driver||Gold||45.2 10 6|
|Driver||Aluminum||37.7 10 6|
|Driver||Tungsten||19 10 6|
|Driver||Brass||15.5 10 6|
|Driver||Iron||9.93 10 6|
|Driver||Stainless steel (WNr. 1.4301)||1.36 10 6|
|Semiconductor||Germanium (doping <10-9)||two|
|Semiconductor||Silicon (doping <10-12)||0.5 10 -3|
|Electrolyte solution||Seawater||approx. 5|
|Electrolyte solution||Drinking water||approx. 0.05|
|Electrolyte solution||Distilled water||5 10 -6|
|Insulating||Typical insulator||<10 -8|
Specific conductance is strongly temperature dependent, so the values only apply at 25 ° C.
With increasing temperature, the vibration of the web in the material becomes higher. This disturbs the electrons as they flow and therefore the electrical conductivity decreases with increasing temperature. electrical conductivity examples
We have divided the table into conductor, semiconductor, electrolyte and insulator groups.
It can be seen that copper has the second highest electrical conductivity , this is why copper wires are used very often in electronics. Silver has an even higher conductivity, but it is much more expensive than copper.
The comparison between seawater and distilled water is also interesting. Here the electrical conductivity is due to the ions dissolved in the water. Sea water has a very high percentage of salt, which dissolves in water. These ions transfer the current. There are no dissolved ions in distilled water, so the current can hardly flow. Therefore, the electrical conductivity of seawater is much higher than that of distilled water.