why power adapters all over-voltage?

You can cream asparagus, but you can't pea soup.

Huh? What's this supposed to mean?

I like Jake's quickie from 2.5 Men: "Two muffins are baking in the oven. One muffin says, "Boy, sure is hot in here." The other muffin says, "Oh, my God! A talking muffin!""

Wanna hear the world's worst joke?

Q: Why do cows wear bells? A: Because their horns don't work.

Cheers! Rich

"Rich Grise"

Well, she was out standing in her field ...

.... Phil

I went to a museum and asked how old the d "Well, I've been working here for 13 years, and when I started they told me those bones were 65 million years old."

-Bill

Your keyboard is obviously a racing keyboard. That's why there is no NASCAR key. Eric

No, these things have capacitors which charge to a peak voltage, which is what you're measuring with your high-impedance multimeter.

You're forgetting about peak versus RMS voltages.

For instance, to make a 12V wall bug, we will take a 10:1 transformer, which gives us 12V AC RMS. This will rectify to a fluctuating DC, which is also 12V RMS.

That fluctuating DC will charge the internal capacitor to about 17V: its peak voltage (12 / 0.707).

The wall bug would have this behavior even if it were made up out of superconductive components. It contains reactances; it is not a battery with an internal resistance. That model does not apply.

The internal resistance of a battery-like voltage source will reduce voltage in proportion to the current demand (Ohm's law).

The wall bug's voltage drop is different. With increasing loads, the average of its increasingly rippling voltage will go down toward the RMS value, but near the RMS value, it should stiffen up and show a different voltage drop behavior from there toward zero ohms.