> You are correct that a battery can in fact be damaged by to much amperage. > But this damage is only because it wasn't trickle charged (low amperage) but > instead quick charged (high amperage). But then again that doesn't stop many > manufactures from making such chargers. As far as the diode, you half > correct. A diode can in fact be damaged by over amperage since it's a > component that does run inline of a wire. But the truth of that is only if it > flows that much. Now to flow that much current there must be something > drawing that much on the other end and it's overloading it's ability. > > So, lets make an example, a simple circuit if you will. Imagine an AC power > supply, say supplying a 12v 2amp signal. On both power leads a diode (cathode > and anode pointing in opposite directions on either pole) and a LED in > parallel to the supply (hope that makes sense), anyway, if the LED is rated > at a minute 50ma, it's using that full 50ma supplied by the supply even > though the supply is capable of flowing 2A. So what will the diodes see, > exactly, 50ma across both. Ok, lets say the diode has a 1A threshold and > instead of a LED you use a 2A lamp, then the diodes will see a 2A load which > after time will burn them out. So anyway, I've still made my point. Amperage > pull will only be what is used, not what the battery or supply can produce. > And as long as you design your circuit correctly (with the correct parts for > the demands), you won't have to deal with blown diodes for example. > > Jake
I don't want to clog this list with a lengthy tutorial on electricity, but I also want to save you from trashing any more Powerbooks. It's my occupation to educate, so here goes one last try (sorry, listers; I can't help it!). You're confused about several fundamental concepts, but let's just look at one. Yes, if you have two power supplies, each, say, 12V, but rated for different maximum currents, the same load connected to each will in fact draw the same current. That's what you probably meant by devices drawing what they will. That's because the current drawn by an element is a function of the voltage you apply across it (as in ohm's law, which applies to resistors), not of the label printed on the side of the power supply indicating its maximum current capability. All absolutely true, and all *absolutely irrelevant* to why you (probably) fried your Powerbook. Unlike this example, you *didn't* apply the rated voltage. You in fact applied a much *bigger* voltage. That's a different situation altogether. And then your Powerbook stopped working after a bit. No surprise there. It's okay not to have a very good grasp of electrical fundamentals (nobody knows everything, and electronics sure is more complicated than a lot of other subjects), but it's less ok that you think you understand much more than you actually do (to the point that you want to debate about it). Please think about why it is that power supplies come in a variety of voltages. It has to do with the fact that electrical devices in fact don't "know" what the "right" current is for them. Do think about that the next time you risk blowing up a perfectly fine Powerbook. :-( And please don't test out your theories by comparing the buzz you get on your tongue with a 9V battery, versus what you get with 120V line power! -- Prof. Thomas H. Lee Center for Integrated Systems, CIS-205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu 650-725-3709 voice, -3383 fax -- PowerBooks is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> PowerBooks list info: <http://lowendmac.com/lists/powerbooks.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/powerbooks%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
