An iron arrowhead has an initial charge of 2.100e-6 C. How many electrons are required to give it a charge of −2.82 μC?(adsbygoogle = window.adsbygoogle || []).push({});

I know that e (the elementary charge) = +/- 1.602E-19 C

And N is the number (or excess charge)

I tried solving this problem 2 ways. The first way:

(2.100E-6 - 2.82E-6)/1.602E-19

I got 4.45E12 electrons

The second way I did:

2.100E-6-1.602E-19 * N = -2.82E-6

-1.602E-19 * N = -2.82E-6 - 2.100E-6

N =-4.92E6/-1.602E19

N= 3.05E25 electrons

However, my homework says it's wrong I tried typing them in with a negative sign, it's wrong. I tried rounding to the nearest electrons, still wrong.

What am I doing wrong? I really have no idea!

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# Homework Help: Electrostatics: Creating Charged Objects

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