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nichrome wire Answered

I got some nichrome wire off eBay, and it works great but when I connected it to a 9 volt battery it barley got hot, then I attached it to 4 x AA batteries and it got red hot. why is this? I don't understand because the 9 volt gives out 9 volts(duh) , but the 4x AA batteries only gives out 6 volts.



10 years ago

ok, how do amps work? is it like, more batteries = more amps?

To NachoMahma:
I used my multimeter to measure their voltages and the 9volt was just under 9 volts, and the 4x AA's pt out about 6.5 volts.

> is it like, more batteries = more amps?
. That's a pretty good rule-of-thumb.
> 9volt was just under 9 volts, and the 4x AA's pt out about 6.5 volts
. Measure under load. Both will drop. I'm guessing the 9V drops a lot more.

Would total battery volume divided by voltage be more accurate? Assuming identical chemistry...

. Current capacity divided by volume would probably be a more useful figure.

more batteries more amps ONLY if they are wired in paralelle. in series, more batteries more volts

Batteries have an internal resistance that limits the flow of current. A look at the duracell oem website shows that a 9 volt has an internal resistance of 1700 milli-ohms. a double A has an internal resistance of 81 milli-ohms, even with four batteries in series, if all else were equal, the AA's can deliver 4x the current.


10 years ago

I'm still confused, doesn't that mean that the 9 volt should make the nichrome get hotter because it has more voltage which equals more current flow? or does it mean that the 9volt has more voltage but less current flow, and the 4x AA has less voltage but more current flow to its ability?

. Battery voltage ratings are at no load. That's why I thought measuring the voltage under load might give you some insight. It appears that your 9V cannot put out the current required, whereas the 4xAA will. . If a battery cannot maintain it's voltage under load, it doesn't matter what the voltage rating is. If both batteries could put out unlimited current, the wire connected to the 9V would get hotter (or burn out faster).

in that case they gave the amperage of a AA*4. thats considerable amperage on nichrom, and the reason your system was heating up.

the nine volt probably can't put out enough amps. the AA's at a lower voltage will have a lower max amps (ohms law) but at least it'll be able to reach it.

. Check the voltage under load (with the nichrome wire hooked up). I'll bet your 9V battery is not putting out 9V.

Check the amps they put out (and were your AAs connected in series or parallel?)