# Calculate power $P=V \times I$

I have an adapter which mentions like this...

Input: 100-240V~1.8A
50-60hZ


So how much power does it really consume?

I just knew Power = Volts X Current. But not sure how to apply the value since the volts is mentioned as 100-240V the value.

Sorry for a very basic question....

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It's impossible to deduce the actual avarage power consumption from these specification. –  leftaroundabout Jun 14 '12 at 10:35

Take whatever your wall supplies (110V, 220V, etc.), and multiply it by 1.8A. Note that this is maximum power usage, not constant.

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110V or 220V is rms, not peak –  Mark Eichenlaub Dec 23 '12 at 16:42
$$V(t)=V\sin(\omega t), I(t)=I\sin(\omega t)$$ thus, $P=V(t)\times I(t)=V\times I\times \sin(\omega t)^2$, where $V$ and $I$ are the r.m.s. values.
Accordingly using $V_{rms}=\frac{V_{given}}{1.414}$ and similarly for $I$, and putting $\omega = 2 \pi\times f$, where $f$ represents the frequency.