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A change variable is a physical variable - or a change process is a process - with instantaneous values that have a periodic time course with a vanishing equivalent value.

The term has a special meaning in electrical engineering when used as alternating voltage and alternating current . The term is treated in more detail under these key words. In acoustics and sound engineering, alternating quantities occur, for example, as sound pressure and sound .

The periodically repeated fluctuations in time of alternating quantities in a system are referred to as oscillations ; they are by no means tied to the sinusoidal shape .

In contrast to the alternating variable, there is the constant variable with a time-constant course and an equivalent value that is not necessarily zero; see DC voltage , DC current .


Many electrical engineering textbooks, for example

  • Karl-Heinz Locher, Hans Müller, Thomas Harriehausen, Dieter Schwarzenau: Moeller basics of electrical engineering. Vieweg + Teubner, 2011, p. 293
  • Wilfried Weißgerber: Electrical engineering for engineers 2. Springer-Vieweg, 2013, p. 1
  • Ralf Kories, Heinz Schmidt-Walter: Pocket book of electrical engineering. German, 2008

Individual evidence

  1. DIN 5483-1 Time- dependent quantities - designation of the time-dependency. 1983, no.2.1