Written by Adeel Abbas
Electrical conductivity depends on the nature of the material. The higher the electrical conductivity the greater the number of ions (charged particles) in the substance.
Ions in a metal are usually the most electrically conductive because they are bound to the metal atoms, and not as mobile as those in a non-metal. Conductivity is measured in terms of the ohm (an international unit of measure for resistance).
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One ohm is equivalent to one volt/ampere, so 1 ohm = 1 V/A. For a given length of wire, the smaller the diameter of the wire the less voltage it will carry. The resistivity of a substance is measured in units called megaohms per meter (1MΩ/m). As conductivity and resistivity increase, the volume of the substance decreases.
Conductivity is determined by two factors: the number of free electrons present, and the movement of these electrons. The more free electrons, the more conductivity and hence the less resistance. This is known as the electronic conductivity.
The movement of the electrons can be affected by the number of crystal defects within the structure, which results in an increase in resistance. This is known as the ionic or lattice conductivity.
Electrical conductivity is measured using a device called an Ohmmeter which measures the resistance of a substance to the flow of current. Resistance to the flow of electricity is proportional to the conductivity of the substance. Resistance of a substance is determined by the number of ions in the material and how close the ions are to the surface.
High conductivity materials are used to carry electric current, and to insulate wires, cables and conductors. Insulation of an electrical circuit is necessary to prevent the flow of unwanted currents. A high resistance material, such as wood, is used for the insulation of a circuit and prevents a short-circuit.
Electrical conductivity is also used to measure the quality of certain chemicals. If a chemical solution has high conductivity, this means that the dissolved ions (such as sodium chloride) are easily dissolved into the liquid and that the molecules are moving freely.
This means the chemical is a good solvent and is a good conductor of electricity. On the other hand, a poor conductor would have low conductivity, and a good insulator would have low conductivity.