Browse Definitions:
Definition

ohm

The ohm is the standard unit of electrical resistance in the International System of Units ( SI ). Ohms are also used, when multiplied by imaginary numbers, to denote reactance in alternating-current ( AC ) and radio-frequency ( RF ) applications. Reduced to base SI units, one ohm is the equivalent of one kilogram meter squared per second cubed per ampere squared (1 kg times m 2 · s -3 · A -2 . The ohm is also the equivalent of a volt per ampere (V/A).

In a direct-current ( DC ) circuit, a component has a resistance of one ohm when a potential difference of one volt produces a current of one ampere through the component. In AC and RF circuits, resistive ohms behave the same as they do in DC circuits, provided the root-mean-square ( rms ) AC voltage is specified. In AC and RF circuits, reactance exists only when there is a net capacitance or inductance . Capacitive reactances have negative imaginary ohmic values; inductive reactances have positive imaginary ohmic values. The reactance of a particular capacitor or inductor depends on the frequency.

Resistances and reactances are sometimes expressed in units representing power-of-10 multiples of one ohm. A kilohm is equal to one thousand (10 3 ) ohms. A megohm is equal to one million (10 6 ) ohms. Fractional prefix multiplier s are seldom used for resistance or reactances; rarely will you hear or read about a milliohm or a microhm. Extremely small resistances and reactances are usually referred to in terms of conductance.

Also see conductance , Ohm's Law , prefix multiplier s, resistance , reactance , siemens , and International System of Units ( SI ).

This was last updated in March 2010

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

SearchSecurity

  • Web application firewall (WAF)

    A Web application firewall (WAF) is a firewall that monitors, filters or blocks traffic to and from a Web application. WAFs are ...

  • MD5

    The MD5 hashing algorithm is a one-way cryptographic function that accepts a message of any length as input and returns as output...

  • identity theft

    Identity theft, also known as identity fraud, is a crime in which an imposter obtains key pieces of personally identifiable ...

SearchHealthIT

SearchDisasterRecovery

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

  • mass notification system (MNS)

    A mass notification system is a platform that sends one-way messages to inform employees and the public of an emergency.

  • disaster recovery as a service (DRaaS)

    One approach to a strong disaster recovery plan is DRaaS, where companies offload data replication and restoration ...

SearchStorage

  • secondary storage

    Secondary storage is used to protect inactive data written from a primary storage array to a nonvolatile tier of disk, flash or ...

  • VRAM (video ram)

    VRAM (video RAM) is a reference to any type of random access memory (RAM) used to store image data for a computer display.

  • ZFS

    ZFS is a local file system and logical volume manager created by Sun Microsystems to control the placement, storage and retrieval...

SearchSolidStateStorage

  • SSD RAID (solid-state drive RAID)

    SSD RAID (solid-state drive RAID) is a methodology commonly used to protect data by distributing redundant data blocks across ...

  • Tier 0

    Tier 0 (tier zero) is a level of data storage that is faster, and perhaps more expensive, than any other level in the storage ...

  • PCIe SSD (PCIe solid-state drive)

    A PCIe SSD (PCIe solid-state drive) is a high-speed expansion card that attaches a computer to its peripherals.

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close