An difríocht idir athruithe ar: "Friotaíocht agus seoltas leictreach"
Content deleted Content added
No edit summary |
No edit summary |
||
Líne 63:
seoltóirí éagsúla: Mar shampla, tá seoltacht [[fluarapolaiméir]] shintéiseach 'Teflon' thart ar 10<sup>30</sup> uair níos ísle ná seoltacht chopair. Cén fáth a bhfuil a leithéid de dhifríocht ann? De gnáth, bíonn líon mór leictreon "dílogánaithe" ag miotal nach bhfuil greamaithe in aon áit amháin, ach saor chun bogadh trasna achar mór, cé go mbíonn, i inslitheoir (cosúil le Teflon), gach leictreon ceangailte go docht le móilín amháin, agus tá fórsa mór ag teastáil chun é a aistharraingt. Luíonn [[Leathsheoltóir|Leathsheoltóirí]] idir an dá dhála.
Athraíonn an friotachas le teocht. I leathsheoltóirí, athraíonn an friotachas freisin nuair a dhíritear solas air. Pléitear iad seo thíos.
==Friotaíocht a thomhas==
Tugtar an t-ainm [[óm-mhéadar]] ar an ghléas a úsáidtear le haghaidh na friotaíochta a thomhas. Níl óm-mhéadiar shimplí in ann friotaíocht íseal a thomhas go cruinn, toisc go gcuireann fiotaíocht na sreang thomais sa bhfeiste tomhais, a bhíonn freagrach as tim voltais, isteach ar an tomhas. Mar sin, úsáidtear gléasanna níos baichte, a leithéid agus [[gléasanna braite ceithre-theirminéal]].
==Friotaíochtaí tipiciúla==
{| class="wikitable"
|-
|'''Comhábhar'''
|'''Friotaíocht''' (Ω)
|-
|1 méadar de shreang chopair<br>le trastomhas 1mm
|0.02<ref>Tá friotachas copair 1.7×10<sup>-8</sup>Ωm. See [http://hypertextbook.com/facts/2004/BridgetRitter.shtml].</ref>
|-
|1 km [[líne chumhachta lastuas| línte cumhachta lastuas]]<br>''(tipiciúil)''
|0.03<ref>''Electric power substations engineering'' by John Douglas McDonald, p 18-37, [http://books.google.com/books?id=e__hltcUQIQC&pg=PT363 google books link]</ref>
|-
|[[Cadhnra AA]] ''friotaíocht inmheánach''<br>(tipiciúil)
|0.1<ref>[http://data.energizer.com/PDFs/BatteryIR.pdf] For a fresh Energizer E91 AA alkaline battery, the internal resistance varies from 0.9Ω at -40°C, to 0.1Ω at +40°C.</ref>
|-
|[[Bolgán solais ghealbhruthacha]]<br>filiméid ''(tipiciúil)''
|200-1000<ref>A 60W light bulb in the USA (120V [[mains electricity]]) draws RMS current 60W/120V=500mA, so its resistance is 120V/500mA=240 ohms. The resistance of a 60W light bulb in Europe (230V mains) would be 900 ohms. The resistance of a filament is temperature-dependent; these values are for when the filament is already heated up and the light is already glowing.</ref>
|-
|Corp an duine
|1000 to 100,000<ref>100,000 ohms for dry skin contact, 1000 ohms for wet or broken skin contact. Other factors and conditions are relevant as well. See [[electric shock]] article for more details. Also see: {{cite web|url=http://www.cdc.gov/niosh/docs/98-131/overview.html|accessdate=2008-08-16|title=Publication No. 98-131: Worker Deaths by Electrocution|publisher=[[National Institute for Occupational Safety and Health]]}}</ref>
|}
{{Fréamh an Eolais}}
| |||