Introduction: Calculating Power (Interactive!)


Watch the video to learn more about how to calculate power in a circuit using a simple equation to work out the power consumed in Watts. Apply it to any device or circuit.

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ThomasK19 (author)2016-06-24


Sutty5 (author)ThomasK192016-06-24

I'm not sure what your question is here?

ThomasK19 (author)Sutty52016-06-24

The video shows the formula P=IV. This is wrong. I is the symbol for current, and A (Ampere) is the unit. V (Volt) is the unit of voltage but the symbol for voltage is U. P is the symbol for power and its unit is W (Watt) or VA (Volt Ampere). So you either need to write P=UI or 1W = 1V*1A.

Sutty5 (author)ThomasK192016-06-24

I understand that many europeans use U as the symbol for voltage. But most use the SI Unit; V. The aim of my videos is to keep it simple, and explaining the differences between symbols can cause confusion. Perhaps a separate video for this in the future. All-in-all, the calculation works the same whether you use a U or V to represent voltage. P=UI is the same as P=IV. I think it's unfair to state that it's wrong, It's just a matter of preference and how you were taught.

ThomasK19 (author)Sutty52016-06-24

I was not aware of the SI system (probably like most US people are not aware of a metric system). But then this system states the symbol for current is A and for wattage its W (always the same as the unit: and So if you reference the SI system you would need to specify W = VA.

Sutty5 (author)ThomasK192016-06-24

Again, this is a matter of where you were taught and your preferences.

This is the SI Notation system I was taught:

If you prefer to use those symbols, I have no issues with that. But as I said, it's not really acceptable to state that either method is wrong given that there are many acceptable variations of notation.

ThomasK19 (author)Sutty52016-06-24

Well, that now makes the confusion perfect. A system where you can choose amongst a variety of symbols to denote a physical size? The site you reference is simply wrong. You need to cite NIST in that place: and they use W for wattage.

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