- #1

popo902

- 60

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## Homework Statement

What are (a) the charge (in C) and (b) the charge density on the surface of a conducting sphere of radius 0.21 m whose potential is 290 V (with V = 0 at infinity)?

## Homework Equations

v = kq/r

[tex]\sigma[/tex] = q/SA

SA of a sphere = 4[tex]\pi[/tex]r^2

## The Attempt at a Solution

so this is what i did

i used the first equation and solved for q = Vr/k

i plugged in the numbers

v= 290, r is the same as the radius because its only the surface r = 0.21,

k = 1/(4[tex]\pi\epsilon[/tex])

I got 5.5e11

the right answer is 6.8E-9

Then for the charge density,

i put the numbers in too

but this is also wrong for sure because it uses my q value

I got 9.9e11

the right answer is 1.2e-8

I don't know how i got that far off