Trading voltage for current

[electronpower03]

1.

If you want 20V at 5A, then you must provide 5V at 20A (not counting losses due to inefficiency). In other words, to get 100W out, you must put 100W in.

Small batteries cannot provide that many watts.
I believe a string of 4 D batteries might be able to provide over 10 A at 5V.

2.

The Ehow page has a misstatement or two.
You can get more AC current through a capacitor by increasing its Farad value, but for that to happen, the AC source needs to be able to provide that much current.

As for DC, the capacitor blocks DC as soon as it has charged sufficiently.



It claims that a diode will increase current. This works in the sense that an AC waveform has a zero net average value..., however when you take one half of it (by rectifying it), then it gives you a waveform which can do things that AC cannot. You're taking either the positive or negative power and that is 50 percent of the original.

Roger that.


So, Wikipedia's page on USB says 5A can be drawn.

https://en.wikipedia.org/wiki/Universal_Serial_Bus

It says, for charging specs only.

So, do you know how to configure a plug for such? I've tested a few... so 0.2, 0.5, others 1.5... and a surprising 3A burst draw!!

Clearly, different plugs are configured for different max current draw.

How does one go about it? Or is the information on the Wikipedia page wrong?