# Finding the Net charge

#### sheri1987

1. Homework Statement

A metal sphere has a charge of +8.0 µC. What is the net charge after 9.00 *10^13 electrons have been placed on it?

2. Homework Equations

q=Ne where q is the charge, N is the number of electrons, and e is given as 1.6*10^-19

3. The Attempt at a Solution

Well the problem gives us a charge, q, and the N, number of electrons, so I figure somehow I need to use this equation. I am not sure where to start though, could someone get me started? Thanks!

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#### Kurdt

Staff Emeritus
Gold Member
The electrons have a negative charge. That charge will be given by the product of the number of electrons and the charge of the electrons. Since the sphere starts with a positive charge the net charge will be the initial positive charge plus whatever charge all the electrons have. Be careful with signs here.

#### sheri1987

I'm still having trouble...what number needs to be negative?

#### Kurdt

Staff Emeritus
Gold Member
Electrons have a negative charge.

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