CHEMISTRY GLOSSARY

electrical current    →   električna struja

Electrical current is a flow of electric charges. The SI unit of electric current is the ampere (A).

ionic current    →   ionska struja

Ionic current is an electric current with ions as charge carriers

diffusion current    →   difuzijska struja

Diffusion current (i_d) is a current which is limited by the speed of particle diffusion in an electrolyte solution.

resistivity    →   električna otpornost

Electrical resistivity, or specific resistance (ρ) is the electric field strength divided by the current density when there is no electromotive force in the conductor. Resistivity is an intrinsic property of a material. Materials with low resistivity are good conductors of electricity and materials with high resistivity are good insulators.

For a conductor of uniform cross section with area A and length L, and whose resistance is R, the resistivity is given by

The SI unit is Ω m.

electric cell    →   električni članak

Electric cell (battery) is a device that is capable of changing some form of energy, such as chemical, nuclear or radiant energy, into electricity. A solar cell, for example, consists of a semiconductor junction that converts sunlight directly into electricity. A dry cell battery converts chemical energy into electricity.

resistance    →   električni otpor

Electrical resistance (R) of a given object is the opposition to the passage of an electric current through that object. The SI unit of electrical resistance is the ohm, represented by the Greek letter omega (Ω). Resistance is the electric potential difference divided by the current when there is no electromotive force in the conductor. This definition applies to direct current. For a conductor of uniform cross section with area A and length L, and whose resistivity is ρ, the resistance is given by

electric field    →   električno polje

If a small amount of charge experience a force, there is an electric field in the vicinity. Electric field E is defined in terms of electrostatic force F that would be exerted on positive test charge q_p placed in the field:

SI unit for electric field is N C^-1, or V m^-1.

The electric field due to a point charge q at distance r from it given by:

where ε₀ is permittivity constant, and is ε_o=8.85×10^-12 C² N^-1 m^-2.

electrical double layer    →   električni dvosloj

Electrical double layer is the structure of charge accumulation and charge separation that always occurs at the interface when an electrode is immersed into an electrolyte solution. The excess charge on the electrode surface is compensated by an accumulation of excess ions of the opposite charge in the solution. The amount of charge is a function of the electrode potential. This structure behaves essentially as a capacitor. There are several theoretical models that describe the structure of the double layer. The three most commonly used ones are the Helmholtz model, the Gouy-Chapman model, and the Gouy-Chapman-Stern model.

laminar flow    →   laminarno strujanje

Laminar flow is a smooth, uniform, non-turbulent flow of a gas or liquid in parallel layers, with little mixing between layers. It is characterised by small values of the Reynolds number.

aluminium    →   aluminij

Aluminium was discovered by Friedrich Wöhler (Germany) in 1827. The origin of the name comes from the Latin word alumen meaning alum. It is soft, lightweight, silvery-white metal. Exposed surfaces quickly form protective oxide coating. Metal reacts violently with oxidants. Third most abundant element in the earth’s crust. Aluminium is the most abundant metal to be found in the earth’s crust, but is never found free in nature. Aluminium is obtained by electrolysis from bauxite. Used for many purposes from airplanes to beverage cans. Too soft in its pure form so less than 1 % of silicon or iron is added, which hardens and strengthens it.