say i use a 9 volt battery to power a small 12volt fan that draws 0.10amps, is there any way to tell about how long the battery would last, i know nothing about Ohms law or whatever so i thought i would ask.
say i use a 9 volt battery to power a small 12volt fan that draws 0.10amps, is there any way to tell about how long the battery would last, i know nothing about Ohms law or whatever so i thought i would ask.
Depends. You aren't running the fan at 12V, so chances are the fan will actually draw LESS current during operation. Worst case scenario, you can probably assume 100mA anyway. Current draw with motors isn't exactly linear, but I didn't really train too much with motors to know for sure.
Also, what's the capacity of the battery? I believe the standard capacity of a standard 9V is around 925mAh. So you'll probably get ABOUT 9 hours of life.
That's a rough estimation, because (1) the fan probably won't draw the full 100mA and (2) once you start draining the battery at a higher rate its effective capacity falls.
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