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02-02-2011, 04:24 PM
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#1 | | RS controls my life!
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| Simple electronics question
I'm a bit confused. Please help.
1. A battery is made from three 2V cells connected in series. If one of the cells is "dead," what is the voltage of the battery? Note that a voltmeter connected to a dead cell reads 0V.
2. A battery is made from three 2V cells connected in parallel. If one of the cells is "dead," what is the voltage of the battery? Note that a voltmeter connected to a dead cell reads 0V.
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02-02-2011, 04:57 PM
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#2 | | Head Moderator
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Series = 4v
Parallel = 2v
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02-02-2011, 05:12 PM
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#3 | | I have named my kids VIC and VLS
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parrallel only adds additional current, series add the voltage
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02-02-2011, 05:12 PM
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#4 | This title intentionally left blank MOD
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What he said. That's really basic ohms law.
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02-02-2011, 05:29 PM
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#5 | | Rs has made me the woman i am today!
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"dead" at time does not equate to 0V...2V cell does not necessarily equate to 2V, usually a little bit higher...
series, gets you the sum of the voltage
parallel, gets you the average of the voltages
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02-02-2011, 07:31 PM
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#6 | | HELP ME PLS!!!
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2nd one will probably be 0 as the dead one will bring the the 2 good ones down.
first one could be 4 or 0. depends if the dead battery is shorted or open cct.
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02-02-2011, 07:35 PM
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#7 | | I WANT MY 10 YEARS BACK FROM RS.net!
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*sigh*
If the "dead" battery is merely drained, it would appear as an open circuit - first example would read 0V, second would read 2V.
If the battery has failed internally and "shorted" (very rare), the first instance would read 4V, second would read 0V, as the dead battery would have drained the good ones, same as shorting a wire across them.
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02-02-2011, 09:22 PM
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#8 | | Rs has made me the woman i am today!
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lol. i think OP is just as confused as he was before.
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02-02-2011, 10:04 PM
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#9 | | Head Moderator
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Originally Posted by Soundy *sigh*
If the "dead" battery is merely drained, it would appear as an open circuit - first example would read 0V, second would read 2V.
If the battery has failed internally and "shorted" (very rare), the first instance would read 4V, second would read 0V, as the dead battery would have drained the good ones, same as shorting a wire across them. | Are you talking about the original question or my comment about a dead cell not conducting?
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02-02-2011, 10:23 PM
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#10 | | I WANT MY 10 YEARS BACK FROM RS.net!
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I was replying to the OP.
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02-02-2011, 10:24 PM
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#11 | | I WANT MY 10 YEARS BACK FROM RS.net!
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| Quote:
Originally Posted by Alatar What he said. That's really basic ohms law. | Kirchhoff's Law, actually.
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02-02-2011, 11:06 PM
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#12 | | Head Moderator
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Originally Posted by Soundy I was replying to the OP. | Ah crap. I'm not sure what I was thinking when I first replied. Some how the bit stating the voltmeter reading the dead cells at 0v didn't sink in...
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02-02-2011, 11:27 PM
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#13 | | I WANT MY 10 YEARS BACK FROM RS.net!
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Originally Posted by Lomac Ah crap. I'm not sure what I was thinking when I first replied. Some how the bit stating the voltmeter reading the dead cells at 0v didn't sink in... | A dead cell would read 0V whether it was shorted or just drained, so it works out the same either way. If it's simply drained, though, it would appear as an "open" circuit to the other cells, and you'd get no current flow at all with them in series. Then only way you'd get a reading is if the cell was shorted internally, which is rare, but I have seen it happen.
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