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 rockreid 25th January 2020 05:02 PM

Electrical Dummy current question

Ok, incorporating a new piece of gear into my 10A breaker home 120v circuit. This new piece of gear consumes 1A from its 5.7V power supply. I am wary of overloading my home 10A circuit and first need to know how much current this new piece of gear is actually going to draw from it. Basic electrical question I know but still would like to verify before the new gear is delivered and I risk blowing my breaker just plugging it in.

 Jay Rose 25th January 2020 06:16 PM

You can't know for sure, since power supply circuits (and even wall warts) differ. All you know is that its output is 5.7 V, 1 A... or ~6 watts.

But understand this: anything the power supply consumes that doesn't turn into the ~ 6 w needed by the circuit has to be turned into some other form of energy*. Usually that's heat, but it could also be sound or light. So unless the supply runs incredibly hot (or bright), I wouldn't expect it to draw much more than 100 mA from a 110v wall outlet.

If you want to know for sure, invest in a Kill A Watt or similar plug-in meter. They run about \$25, and every studio and/or homeowner should have one.

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* Or mass. E=mc^2. ; )

 Philbo King 10th February 2020 06:24 PM

Here's how to do this:

1 Amp x 5.7 V = 5.7 Watts

5.7 Watts / 110 V = 0.0518 Amps

So, at the 110V level, it will draw an additional 0.05 (or 1/20 of an amp) if you exclude the power that is wasted as heat by the wall wart, which should be neglible.

I wouldn't sweat it too much, just plug it in, you'll be fine.