- #1

Aleksandre

- 11

- 0

## Homework Statement

How much work should be done on a point charge of q=15 nC to bring it from infinity to a distance of 3 cm from a surface of a charged sphere? Diameter of sphere is 15 cm, its surface charge density is 12 microC/cm

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## Homework Equations

W=deltaU=q*deltaV

v=kQ/r

W=deltaU=q(kQ/Rf -kQ/Ri)

## The Attempt at a Solution

If point charge is placed in infinity then initial distance would be infinity which means kQ/Ri=0. Then we are left with equation:

W=q(kQ/Rf).

k is constant, q is known=15 nC and Rfinal=0.03 meters as given. The only uknown would be Q, e.i charged sphere. Now I have everything but have no idea how to calculate Q. Can you assist me?

Thanks.