# calculating needed electrons to give a specific charge

1 vote
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I have a neutral object, and the question is asking how many electrons needed to be added to it to give it a charge of -1 C.

After looking at my notes, I was thinking of using the Qnet equation (#e-)(-e) = -1C

so to get (#e-) I plug in 1.602 10^-19C and divide -1C by that, to get -1.602 10^-19 for number of electrons.

I know this is probably wrong, but I was hoping someone could help clear my confusion. I tried researching this problem and saw a similar question on yahoo answers, but the explanations just answered instead of explaining in detail, and my book doesn't have answers that are quite as similar. I thought the concept was clear enough but the numbers just seem a little weird so I was hoping can someone please clear this confusion?

1 vote

You are almost correct. Your calculation is upside down. It should be

$N_e=\frac{-1C}{-e}$.

You should be expecting an answer which is a large number, because electrons are small so the charge on them is small. A number of electrons of $1.6 \times 10^{-19}$ is very much less than 1, so it cannot be correct.

answered Jun 7, 2017 by (27,556 points)