Browse Definitions:
Definition

# volt-ampere (VA)

Contributor(s): Guillermo Cardenas

Volt-ampere (VA) is a measurement of power in a direct current ( DC ) electrical circuit. The VA specification is also used in alternating current ( AC ) circuits, but it is less precise in this application, because it represents apparent power , which often differs from true power .

In a DC circuit, 1 VA is the equivalent of one watt (1 W). The power, P (in watts) in a DC circuit is equal to the product of the voltage V (in volt s) and the current I (in ampere s):

P = VI

In an AC circuit, power and VA mean the same thing only when there is no reactance . Reactance is introduced when a circuit contains an inductor or capacitor . Because most AC circuits contain reactance, the VA figure is greater than the actual dissipated or delivered power in watts. This can cause confusion in specifications for power supplies. For example, a supply might be rated at 600 VA. This does not mean it can deliver 600 watts, unless the equipment is reactance-free. In real life, the true wattage rating of a power supply is 1/2 to 2/3 of the VA rating.

When purchasing a power source such as an uninterruptible power supply ( UPS ) for use with electronic equipment (including computers, monitors, and other peripherals), be sure the VA specifications for the equipment are used when determining the minimum ratings for the power supply. The VA figure is nominally 1.67 times (167 percent of) the power consumption in watts. Alternatively, you can multiply the VA rating of the power supply by 0.6 (60 percent) to get a good idea of its power-delivering capability in watts.

Also see current , voltage , power , reactance , and watt .

This was last updated in March 2011

#### Join the conversation

Send me notifications when other members comment.
600VA mean Watts.. This one correct orb wrong
Cancel

I want to purchase a less expensive AC adaptor than the one the manufacturer advertises for a blood pressure monitor.

The input rating for the manufacturers adaptor is 100-240V 50/60Hz 15VA.  No output rating is given.

Input: 100-240V 50/60Hz 0.3A

Output: 6V = 2000mA

Can I use this adaptor safely?

Cancel
Can i input DC 12volt. in a audio system which has 9volt ----mA power input.?
will that be ok?
Cancel

## SearchCompliance

• ### risk map (risk heat map)

A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces.

• ### internal audit (IA)

An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

• ### pure risk (absolute risk)

Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...

## SearchSecurity

• ### FIDO (Fast Identity Online)

FIDO (Fast ID Online) is a set of technology-agnostic security specifications for strong authentication. FIDO is developed by the...

• ### cryptanalysis

Cryptanalysis is the study of ciphertext, ciphers and cryptosystems with the aim of understanding how they work and finding and ...

• ### Trojan horse (computing)

In computing, a Trojan horse is a program that appears harmless, but is, in fact, malicious.

## SearchHealthIT

• ### HITECH (Health Information Technology for Economic and Clinical Health) Act of 2009

The HITECH (Health Information Technology for Economic and Clinical Health) Act of 2009 is legislation that was created to ...

• ### Epic Systems

Epic Systems is one of the largest providers of health information technology, used primarily by large U.S. hospitals and health ...

• ### accountable care organization (ACO)

An accountable care organization (ACO) is an association of hospitals, healthcare providers and insurers in which all parties ...

## SearchDisasterRecovery

• ### business continuity and disaster recovery (BCDR)

Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

• ### business continuity plan (BCP)

A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

• ### call tree

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

## SearchStorage

• ### SSD TRIM

SSD TRIM is an Advanced Technology Attachment (ATA) command that enables an operating system to inform a NAND flash solid-state ...

• ### cloud storage service

A cloud storage service is a business that maintains and manages its customers' data and makes that data accessible over a ...

• ### cloud hosting

Cloud hosting is the process of outsourcing an organization's computing and storage resources to a service provider that offers ...

## SearchSolidStateStorage

• ### hybrid hard disk drive (HDD)

A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.

Close