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Glossary of electrical terms

Glossary of electrical terms

Electrician deals with installation, repair and maintenance of electrical systems. This profession requires not only mastering the ability to design according to technical standards, perform inspections of equipment or operate it, but also to learn basic terms. Here is an electrical dictionary that introduces selected topics in this field.

Electric current

Electric current refers to the orderly movement of electric charges – carriers that produce an electric field. Charges can be either positive or negative. They move in different directions. A current only flows when a lower potential is applied to a conductor with a higher potential.

AC current

AC current is alternating current, a type of alternating current with specific periodicity and variation in the direction of flow. In commonly used electrical systems its waveform is sinusoidal, e.g. in domestic systems.

DC current

DC current is a direct current generated by a constant voltage source – one that does not change over time. In this case, the electrons travel at a constant speed that depends on the magnitude of the voltage and the resistance of the circuit.


An ampere is the basic unit of electric current, denoted by the symbol [A]. In the SI system, it is defined by taking a specific numerical value of the elementary charge.


A watt is a unit of power and flux, denoted in the SI system by the symbol W. One watt represents the power at which work will be done in one second. This unit is named after the British inventor and engineer, James Watt.


An ohmmeter is a measuring instrument that is used to measure resistance. These devices make use of Ohm’s law, i.e. the relationship between current and voltage on a selected element of the system. The unit used in this case is ohm, denoted by [Ω].


An inverter is a device that converts direct current to alternating current with a controllable output frequency. Inverters are used in various types of converters, allowing to connect equipment powered by alternating current.

Power demand

The power demand is a value that determines the electricity demand of a building or part of a building. This parameter is determined based on the power balance, i.e. the sum of the power of all the installed electricity receivers multiplied by the simultaneity coefficient – which defines the probability of simultaneous use of all these receivers. The type of protective devices used, as well as the amount of fixed electricity charges, depend on the value of the power required.


IK is a parameter determining impact resistance, which is a value characterizing devices and elements of electrical systems – e.g. enclosures of electrical switchboards. This classification allows the rating of resistance to mechanical effects, including impact, pressure or drop. The IK parameter is completed with a number from 0-10 range, where IK00 means no impact resistance at all and IK10 means highest impact resistance.


IP stands for International Protection. This code is used to mark electrical equipment units for information purposes, as it allows to determine the level of tightness of their enclosures. The IP scheme consists of a sequence of at least two digits and in some cases an additional two letters. The first digit indicates dustproofness, and the second one waterproofness of the enclosure, so the least protected are marked as IP00, while the highest degree of protection is IP68.

Protection class

The protection class is a conventional designation for the electric shock safety of electrical equipment and components. There are four classes – 0, I, II and III. The lowest value means the least effective protection, protecting only against direct contact. Class III, on the other hand, refers to the greatest protection, in the form of a so-called touch voltage reduced in relation to the mains voltage of the current (below 50 V for alternating current and below 120 V for direct current).

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