Encyclopedia @ Vestigatio Search
Web    Encyclopedia    News    Blogs    Forums   

Ohm


The ohm (symbol: O) is the SI unit of electrical impedance or, in the direct current case, electrical resistance, named after Georg Ohm.

Definition


The ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.BIPM SI Brochure: Appendix 1, p. 144

     \Omega = \dfrac{\mbox{V}}{\mbox{A}} = \dfrac{\mbox{m}^2 \cdot \mbox{kg}}{\mbox{s}^{3} \cdot \mbox{A}^2}

The most commonly used multiples and submultiples in electrical and electronic usage are the milliohm, ohm, kilohm, and megohm.

Conversions


A measurement in ohms is the reciprocal of a measurement in siemens, the SI unit of electrical conductance. The non-SI unit, the mho (ohm written backwards), is equivalent to siemens but is mostly obsolete and rarely used.
Ohms to watts: The power dissipated by a resistor may be calculated using resistance and voltage. The formula is a combination of Ohm's law and Joule's law:
     :P={V^2 \over R}
     where P is the power in watts, R is the resistance in ohms and V is the voltage across the resistor.

     This method is not reliable for determining the power of an incandescent light bulb, resistance heater or electric short since all these devices operate at high temperatures and the resistance measured using a meter will not represent the operating resistance. For these conditions instead multiply V by current in amperes to get power in watts.

See also


Ohm's law
Resistor
Resistivity
abohm
Siemens (unit)

External links


Scanned books of Georg Simon Ohm at the library of the University of Applied Sciences Nuernberg
Official SI brochure
NIST Special Publication 811
History of the ohm at sizes.com

   
   
This section is sponsored by:

ohm
Don't just search for ohm, find results.
www.ask.com


Limited Offer
How About Take 3 Seconds to Enter Postal Address to Claim Your Free Laptop Now while you are looking for Ohm?
www.RewardLaptop.com


Ohm
Find Ohm info here!
www.dealrain.com


Better Results For Ohm
Find ohm results and other info here!
www.dealshine.com


Laptops
Find a great deal on a Laptop Computer by browsing our Laptop Computer listings.
www.LaptopComputersInfo.com


laptops
Don't just search for laptops, find results.
www.ask.com


Extreme Laptop Sale
Ultra Performance Notebook Systems Save up to $2000 on special units!
www.notebookchoice.com


Laptop
Laptop At Huge Discount! Free Shipping On Laptop.
www.insights1.com




©2008 Vestigatio