Calculating Net Charge on a Metal Sphere with Added Electrons

[osulongboard]

Homework Statement

A Metal sphere has a charge of +6uC. What is the net charge after 1*10^14 electrons have been placed on it?

Homework Equations

Single Electron - -1.6*10^-19

The Attempt at a Solution

1st. Convert +6uC to 1.6*10^-6 (is this right?)
2nd. (-1.6*10^-19)(1*10^14)=1.6*10^-5
3rd. (6*10^-6)+(1.6*10^-5)= 2.2*10^-5 (?)


I don't think this is a very hard problem but i want to make sure I am doing the basics right. Thanks in Advance!

 

[mikelepore]

1st. Convert +6uC to 1.6*10^-6 (is this right?)

No. Changing "micro" to 10^-6 is like moving a decimal point, without changing the digits. You can't change the 6 to a 1.6

 

[tomcue]

Your calculations are correct. To double check, you can also calculate the net charge using the formula Q = Ne, where Q is the net charge, N is the number of electrons, and e is the charge of a single electron. In this case, Q = (1*10^14)(-1.6*10^-19) = -1.6*10^-5 C, which is equivalent to -16 uC. This matches your answer of 2.2*10^-5 C, since +6 uC and -16 uC give a net charge of -10 uC. Overall, your approach and calculations are correct.