AskDefine | Define hertz

Dictionary Definition

Hertz

Noun

1 the unit of frequency; one Hertz has a periodic interval of one second [syn: Hz, cycle per second, cycles/second, cps, cycle]
2 German physicist who was the first to produce electromagnetic waves artificially (1857-1894) [syn: Heinrich Hertz, Heinrich Rudolph Hertz]
3 German physicist who with James Franck proved the existence of the stationary energy states postulated by Bohr (1887-1975) [syn: Gustav Hertz, Gustav Ludwig Hertz]

User Contributed Dictionary

English

Etymology

Named after the German physicist Heinrich Rudolf Hertz.

Pronunciation

Noun

  1. In the International System of Units, the derived unit of frequency; one (period or cycle of any periodic event) per second. Symbol: Hz

Translations

  • Chinese: (hè), 赫兹 (hèzī)
  • Finnish: hertsi
  • French: hertz (a preceding vowel is not elided; p: hertz)
  • Italian: hertz (p: hertz)
  • Japanese: ヘルツ (herutsu)
  • Polish: herc
  • Russian: герц (gerts)
  • Spanish: hercio , hertz (p: hertz)
  • Swedish: hertz

See also

French

Pronunciation

  • lang=fr|/ɛʁts/
  • SAMPA: /ERts/

Noun

  1. hertz
  2. plural of hertz

Related terms

Italian

Noun

hertz (plural: hertz)
  1. hertz
  2. plural of hertz

Related terms

Spanish

Noun

hertz (plural: hertz)
  1. hertz
  2. plural of hertz

Synonyms

Swedish

Noun

hertz (plural: hertz)
  1. hertz (singular and plural)

Extensive Definition

''' The hertz (symbol: Hz) is the International System of Units (SI) base unit of frequency. The definition of the hertz is based upon that for the second, namely: the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9 192 631 770 hertz, \nu (hfs Cs) = 9 192 631 770 Hz.
Its base unit is cycle/s or s-1 (also called inverse seconds, reciprocal seconds). In English, hertz is used as both singular and plural. As any SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 103 Hz), MHz (megahertz, 106 Hz), GHz (gigahertz, 109 Hz) and THz (terahertz, 1012 Hz).
One hertz simply means one cycle per second (typically that which is being counted is a complete cycle); 100 Hz means one hundred cycles 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. The frequencies of aperiodic events, such as radioactive decay, are 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 60 revolutions per minute (RPM) can thus be said to be rotating at ≈6.283 rad/s or 1 Hz, where the latter reflects the number of complete revolutions per second. The conversion between a frequency f measured in Hertz and an angular frequency ω measured in radians/s are: \omega = 2\pi f and f = \omega/(2\pi) \, .

History

The hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1930. It was adopted by the General Conference on Weights and Measures (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 per second (kc/s) and megacycles per second (Mc/s). The term cycles per second was largely replaced by hertz by the 1970s.''
The term "gigahertz", most commonly used in computer processor speed and radio frequency (RF) applications, can be pronounced either /ˈgigaˌhɝts/, with a hard /g/ sound or /ˈʒɪgaˌhɝts/ or /ˈdʒɪgaˌhɝts/, with a soft /ʒ/ sound at the beginning of the word. The prefix "giga-" is derived directly from the Greek "" and hence the preferred pronunciation is /ˈgɪga/. Some electrical engineers use /ˈdʒɪga/, by analogy with "gigantic".

Applications

Vibration

Sound is a traveling wave which is an oscillation of pressure. Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 16 Hz to 20,000 Hz; the average human can hear sounds between 20 Hz and 16,000 Hz. The range of ultrasound, infrasound and other physical vibrations such as molecular vibrations extends into the megahertz range and well beyond.

Electromagnetic radiation

Electromagnetic radiation is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz.
Radio frequency radiation is usually measured in kilohertz, megahertz, or gigahertz; this is why radio dials are commonly labeled with kHz, MHz, and GHz. Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz. Electromagnetic radiation with frequencies in the low terahertz range, (intermediate between those of the highest normally-usable radio frequencies and long-wave infrared light), is often called terahertz radiation. Even higher frequencies exist, such as that of gamma rays, which can be measured in exahertz. (For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)

Computing

In computing, most central processing units (CPU) are labeled in terms of their clock speed expressed in megahertz or gigahertz (109 hertz). The number of megahertz refers to the frequency of the CPU's master clock signal ("clock speed"). This signal is simply an electrical voltage which changes from low to high and back again at regular intervals. Hertz has become the primary unit of measurement used by the general populace to determine the speed of a CPU, but many experts have criticized this approach, which they claim is an easily manipulable benchmark. For home-based personal computers, the CPU has ranged from approximately 1 megahertz in the late 1970s (Atari, Commodore, Apple computers) to nearly 4 GHz in the present. This can be increased even further by increasing the frequency of the CPU in the BIOS or other software.
Various computer buses, such as memory buses connecting the CPU and system random access memory (RAM), also transfer data using clock signals operating at different frequencies in the megahertz ranges (for modern products).

Order of magnitude

Frequencies not expressed in hertz

Even higher frequencies are believed to occur naturally, in the frequencies of the quantum-mechanical wave functions of high-energy (or, equivalently, massive) particles, although these are not directly observable, and must be inferred from their interactions with other phenomena. For practical reasons, these are typically not expressed in hertz, but in terms of the equivalent energy.
hertz in Arabic: هرتز
hertz in Asturian: Herciu
hertz in Min Nan: Hz
hertz in Bosnian: Herc
hertz in Breton: Hertz
hertz in Bulgarian: Херц (единица)
hertz in Catalan: Hertz
hertz in Czech: Hertz
hertz in Danish: Hertz
hertz in German: Hertz (Einheit)
hertz in Estonian: Herts
hertz in Spanish: Hercio
hertz in Esperanto: Herco
hertz in Basque: Hertz
hertz in Persian: هرتز
hertz in French: Hertz
hertz in Galician: Hertz
hertz in Korean: 헤르츠
hertz in Hindi: हर्ट्ज़
hertz in Croatian: Herc
hertz in Indonesian: Hertz
hertz in Interlingua (International Auxiliary Language Association): Hertz
hertz in Italian: Hertz
hertz in Hebrew: הרץ
hertz in Latvian: Hercs (mērvienība)
hertz in Lithuanian: Hercas
hertz in Hungarian: Hertz
hertz in Macedonian: Херц
hertz in Malay (macrolanguage): Hertz
hertz in Dutch: Hertz (eenheid)
hertz in Japanese: ヘルツ
hertz in Norwegian: Hertz
hertz in Norwegian Nynorsk: Hertz
hertz in Polish: Herc
hertz in Portuguese: Hertz
hertz in Romanian: Hertz
hertz in Russian: Герц (единица измерения)
hertz in Albanian: Herci
hertz in Simple English: Hertz
hertz in Slovak: Hertz (jednotka)
hertz in Slovenian: Herc
hertz in Serbian: Херц
hertz in Finnish: Hertsi
hertz in Swedish: Hertz
hertz in Thai: เฮิรตซ์
hertz in Vietnamese: Hertz
hertz in Turkish: Hertz (birim)
hertz in Ukrainian: Герц
hertz in Urdu: ہرٹز
hertz in Contenese: 赫茲
hertz in Chinese: 赫兹
Privacy Policy, About Us, Terms and Conditions, Contact Us
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2
Material from Wikipedia, Wiktionary, Dict
Valid HTML 4.01 Strict, Valid CSS Level 2.1