# Thread: calculate the net charge.

1. ## calculate the net charge.

A metal sphere has a charge of +7.0 µC. What is the net charge after 8.00 1013 electrons have been placed on it?
in µC

anyone able to help me with this one please.

2. Originally Posted by rcmango
A metal sphere has a charge of +7.0 µC. What is the net charge after 8.00 1013 electrons have been placed on it?
in µC

anyone able to help me with this one please.
You mean 8.00 x 10^13 electrons?

Well the charge of a single electron is -1.6 x 10^-19 C. So 8 x 10^13 electrons has a charge of...

-Dan

3. Originally Posted by rcmango
A metal sphere has a charge of +7.0 µC. What is the net charge after 8.00 1013 electrons have been placed on it?
in µC

anyone able to help me with this one please.
Well here's a start: How many coulomb is 8.00 1013 electrons? (You might need to refer to your class notes for the conversion). This NEGATIVE charge is added to +7.0 µC.

4. Originally Posted by topsquark
You mean 8.00 x 10^13 electrons?

Well the charge of a single electron is -1.6 x 10^-19 C. So 8 x 10^13 electrons has a charge of...

-Dan

So couldn't be just -1.6 x 1^-19 C * 8 x 10^13?

then add that to 7uC?

i'm getting confused from sig figs i think.

5. Originally Posted by rcmango
So couldn't be just -1.6 x 1^-19 C * 8 x 10^13? Mr F says: Yes.

then add that to 7uC? Mr F says: Yes.

i'm getting confused from sig figs i think. Mr F says: You wouldn't be the first.
..

6. thanks got it, -5.72 uC

7. ## Still need helpI'm working on the same problem

Except I have
A metal sphere has a charge of +8.0 µC. What is the net charge after 8.00 x 10^13 electrons have been placed on it

Everytime I try doing

(-1.6x10^-19) x (8.00x10^13) + 8 = 7.9999872

But thats not the correct answer.

Why is that not working???

,

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### a metal sphere has a charge of

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