# What Is Alternating Current?

Alternating current is a type of electric current characterized by changing over time, either in intensity or in direction, at regular intervals.

The voltage varies between the maximum and minimum values ​​cyclically, the voltage value is positive half the time (positive half cycle or positive half period) and negative the other half. This means that half the time the current flows in one direction, the other half of the time in the other direction.

The most common form of undulation follows a sine-like trigonometric function, since it is the most efficient and practical way of producing electrical energy using alternators. However, there are certain applications in which other waveforms are used, such as the square wave or the triangle wave.

In general, the electric current is distributed in the form of alternating current at 50 Hz (50 changes per second).

## What is the frequency and period in an alternating current?

The frequency denotes the number of oscillations of a periodic process in relation to the time interval to which this number applies. It is expressed in the Hertz unit with the Hz unit symbol.

A period is the smallest local or temporal interval after which the process repeats. This interval is called a period. For an alternating current, a period is p. B. a successive positive and negative half wave. The period T is equal to the reciprocal of the frequency f.

The best known AC frequency is 50 Hz, the frequency of the public electricity supply network in the European Union. This alternating current has a period of

For an overview of power supply in other countries, see Country overview of connector types, line voltages, and frequencies. Angular frequency is preferred for theoretical calculations, such as for complex calculations of AC w ​​used:

At an alternating current with a frequency of 50 Hz

The lowest alternating current frequency, which is used to some extent in Germany, Austria, Switzerland, Sweden and Norway, is found in the pulling current at 16.7 Hz. The highest frequency for alternating current is given by the possibilities and requirements in radio technology and is of the order of 300 GHz.

## What are coaxial cables and what are they for?

Coaxial cables consist of a conductor arranged along the axis of the cable covered by a tube-shaped screen separated by a dielectric layer. At frequencies above 1 GHz (gigahertz), unprotected conductors lose too much emitted energy as an electromagnetic field, so coaxial cables are used.

The current flowing in the inner conductor is equal and opposite to that flowing in the screen (the outer part of the cable). The electromagnetic field is completely stored in the cable and no energy is released outside of it.

Coaxial cables have significantly less loss for frequencies up to 20 GHz. For microwave frequencies above 20 GHz, the losses (mainly due to the dielectric spread factor) become too great. So the waveguides are already in use.

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Published: March 15, 2017
Last review: March 27, 2020