Hertz

''For the radio pioneer, see Heinrich Rudolf Hertz. For other uses, see Hertz (disambiguation).

The hertz (symbol: Hz) is the SI unit of frequency. In English, hertz is used as both singular and plural.

Definition

One hertz is defined as the reciprocal second.

1 Hz = 1 s⁻¹

SI multiples

Explanation

One hertz simply means "one per second" (1 / s); 100 Hz means "one hundred per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. Frequency of aperiodic events, such as radioactive decays, is expressed in becquerels.

To avoid confusion, periodically varying angles are typically not expressed in hertz, but rather in an appropriate angular unit such as radians per second. A disc rotating at 1 revolution per minute (RPM) can thus be said to be rotating at 0.105 rad/s or 0.017 Hz, where the latter reflects the number of complete revolutions per second.

History

The hertz is named after the German physicist Heinrich Rudolf Hertz, who made important scientific contributions to electromagnetism. The name was established by the IEC in 1930 ^*. It was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples, primarily kilocycles (kc) and megacycles (Mc). Hertz largely replaced cycles in common use by 1970.

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Definition

SI multiples

Explanation

History

See also