What is the difference between watts (volts X amps) and volt amps (volts X amps)?

Answer 1

volt-amperes do not equal watts always. The true formula for watts is VAcos(phase); (phase is the angle between V and A) The number cos(phase) is also called the power factor. Electric machinery is often rated in volt-amperes because the source of power has to be able to supply that much current, regardless how little power is actually drawn. Electric companies do no like loads with low power factor, because they charge for watts (kilowatt-hrs), which may be low, but their circuits and power lines have to carry the full amount of current. The power losses in these parts due to resistance increase with current drawn regardless of the watts used.

Answer 2

Sometimes Watts = VA, sometimes they are different. When you apply voltage to a purely resistive load (heater, light bulb, etc), then the voltage and current are always in phase. In that case the Watts = VA = volts x amps. When you have inductance or capacitance in a circuit, the volts and amps will be out of phase so the actual power is Watts = volts x amps x sin(phase difference), whereas VA is still just volts x amps. In that second case Watts < VA.

Answer 3

In the strictest sense, a volt-amp and a Watt are the same. I expect they are not used to mean the same thing in AC electronics. It would seem that the volt-amp refers to the maximum power flow, while the Watt refers to a time-averaged power flow.
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1 joule = the energy generated when 1 ampere of electrical current, passes through an electrical potential drop of 1 volt. Energy = Volts x Current.

1 watt = 1 joule/second.

So joules is a quantity of energy, and watts is the RATE of generation of energy. Watt = Energy / second.
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VA in AC circuits is "reactive power" and has nothing to do with real power. Loads such as induction motors, do not act as pure resistors, but like inductors. Inductors and capacitors draw AND supply power back into their power source. Induction motors supply current BACK into the power grid every half cycle. These currents tend to somewhat cancel out, but are still there. If I supply 10 amps on a wire for 1 second, then reverse the polarity and try again, the net current flow from end to end was zero, but 10 amps were flowing for 2 seconds.

Answer 4

There is a big difference. If we start with volt - amps, this is the rms voltage times the rms amps. For example 240v x 10amps = 2400 va. This is how most generators and transformers are rated because these parameters are easily measure.
Watts is different because watts is the power input or power output. There is no guarantee that the current peaks at the same time as the voltage, infact can easily peak later or earlier. That is why many motors have a condensor on them, so the current peak occurs closer to the voltage peak. I think they call it phase, and this changes depending on the type of loading.
Power = v x a x phase.

Answer 5

Volt-amp refers to the maximum power flow that happens. Watt is the averaged power flow over a span of time.

It's important to note that AC power changes as the function sin(t). With t being time. Where as DC power is constant. Because of this, a volt-amp would be the same thing as a watt on DC, but would not for AC.

Answer 6

Watts are power. Volt amps are apparent power. Apparent power in inductive loads comes from the current lagging the voltage in that inductive load.It is the additional power required by the inductive load from it's power source, and the resulting stress placed on the power source.

Answer 7

Volt Amps also nown as VA is Watts

Answer 8

In DC power they are same. In AC Watt is averaged power.

Answer 9

Nomenclature. Watt is the correct unit of measure.