# Experiment DC amps to AC watts Conversion



## budgetprepp-n (Apr 7, 2013)

Hi,
I am thinking of doing an experiment with an, inverter, and a light bulb 

I can measure watts when it's in the form of 120 volts AC

I can measure amps when it's in the form of 12 volts DC 

I was thinking of checking the watts of a light bulb using straight 120 volt AC --

Then checking the amp draw using 12 volt DC with an inverter with the same bulb 
if you can convert amps to watts we can see how much is really lost when using an inverter.

Also I would like to do this with a 400 watt inverter and then with a 1500 watt inverter 
to see if inverter size matters 

And if I get all this junk out for an experiment might as well see what the amp draw is on an inverter 
if it's just sitting there "on" but not powering anything. 

To get a more accurate calculation on power loss measurement would I be better off using a true 75 watt
bulb that draws 75 watts rather than a energy saving bulb that only pulls 18 watts?

I can measure 12 volt amps down to 1/10 of an amp 

Will the formula for amps to watts work if your mixing AC and DC?

Would anyone be interested in the results from this?


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## HuntingHawk (Dec 16, 2012)

A 100watt bulb is going to draw 100watts no matter what the power source.


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## budgetprepp-n (Apr 7, 2013)

HuntingHawk said:


> A 100watt bulb is going to draw 100watts no matter what the power source.


yes I agree %100 ,,, But will it take any extra watts to go from a 12 DC battery through an inverter and then to the bulb? 
What I want to know is the amount of watts total being pulled from a 12 volt battery to run that 100 watt bulb
you may be right. It might be a fair exchange of power. 
Will it cost any watts to convert DC to AC? I don't know. I have read a little about it but I like see for myself sometimes.

I don't like to say "I think" I would rather say "I know for sure"


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## HuntingHawk (Dec 16, 2012)

Yes, there is a loss converting DC to AC. Type inverter makes a difference in the percentage.


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## dwight55 (Nov 9, 2012)

If you are going to do this and want to have results you can bank on, . . . ditch the light bulbs, . . . get ceramic resistors. They will have a more dependably uniform ohm resistance and impedance than you will get from run of the mill light bulbs.

You also can put them in a drawer, . . . drag em out every time you want to do calculations, . . . and KNOW you are starting out with the same question every time, . . . whereas bulbs can be broken, burn out, etc.

Here's a link that may also be interesting for you: TheBackShed.com - 200w dump load

May God bless,
Dwight


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## PaulS (Mar 11, 2013)

Volts times amp is always watts - it doesn't matter if it is AC or DC.

Inverters can lose as much as 20% in changing the DC to AC.

All 100 watt bulbs do not use 100 watts - the "watt" rating has become a method to demonstrate the luminosity (brightness) of bulbs. (called watt equivalency)

Even with the old light bulbs the different manufacturers used different voltages to rate their bulbs - GE was infamous for building bulbs rated upon 110 VAC and Sylvania used 120 VAC to rate their bulbs. That is why the GE bulbs didn't last as long as the Sylvania bulbs.


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