Talk:Volt-ampere

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Why does the article claim that the unit's use is restricted to AC circuits when it is perfectly meaningful for DC or any other current flow? 68.238.80.80 19:57, 26 July 2006 (UTC)

Because for Direct Current, we just use watts. A volt is one joule [of energy] per coulomb [of charge]. An ampere is one coulomb per second. Therefore, a volt-ampere (DC) is one joule per second, which is a watt.

The dynamics of Alternating Current, however (which I don't fully understand, and probably never will!), are far more complex. Apparently because current (in AC circuits) often doesn't track voltage directly (for capacitive loads, the current rises and falls ahead of the voltage; for inductive loads, the change in current lags behind it), you can't just multiply volts times amperes to get watts, because the volts and amps don't "line up." So volt-amperes are used instead of watts. See the article on AC power for more information. 24.6.66.193 21:42, 17 August 2006 (UTC)

[edit] Standard watthour meter

I just about understand the difference between a Watt and a Volt Amp. What I am curious about, is is whether a normal domestic electricity meter measures Watt hours or Volt Amp hours. I am finding, in some cases, a factor of six difference between the two statistics on some appliances.

The standard household electrical meter presently measures kWh (energy in kilowatthours) although some of the more advanced meters can also record other quantities such as kilovarhours, peak kVA demand, demand interval data, etc. Industrial and commercial facilities are often billed on VA demand in addtion to kWh. Nearly all households today are billed solely on kWh.

Rcdugan 17:42, 23 June 2007 (UTC)