# Find the charge on the outer surface

## Homework Statement ## Homework Equations

##E=\frac{kQ}{r^2}##

## The Attempt at a Solution #### Attachments

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BvU
Homework Helper
2019 Award
Hello Fatima,

PF is not intended for stamp-approvals. If you convince yourself that -9 nC is the right answer, then that IS your answer for this exercise !

And why shouldn't it be the right answer ?

BvU
Homework Helper
2019 Award
Yeah, well...

Hello Fatima,

PF is not intended for stamp-approvals. If you convince yourself that -9 nC is the right answer, then that IS your answer for this exercise !

And why shouldn't it be the right answer ?
I was not pretty sure. Just wanted to confirm my answer. Sorry for multiple questions but my exam is after hours. I wish I have not broken the forum rules. Thanks

Last edited:
BvU
Homework Helper
2019 Award
Best of luck for your test! • Fatima Hasan
ehild
Homework Helper

## Homework Statement

View attachment 223911

## Homework Equations

##E=\frac{kQ}{r^2}##

## The Attempt at a Solution

View attachment 223912
You wrote that Q=1 nC and then that Q=-10+1 =-9 nC. These are wrong, although the answer "A" is correct. Pay more attention!

• BvU
You wrote that Q=1 nC and then that Q=-10+1 =-9 nC. These are wrong, although the answer "A" is correct. Pay more attention!
##Q_0=-10+1=-9nC##

ehild
Homework Helper
##Q_0=-10+1=-9nC##
-10+1 is not -9 nC . Write out the units at both sides of an equation.

• Fatima Hasan