I have two questions, please help i really need to get this done properly!(adsbygoogle = window.adsbygoogle || []).push({});

The electric field inside a NONCONDUCTING sphere of radius R containing uniform charge densiy is radially directed and has magnitude of

E = qr / 4 pi epsilon0 R^3

where r is the distance from the centre

and R is the radius

q is the charge on the sphere

a) Find potential V inside the sphere taking V=0 @ r = 0

Since V = Integral E dr

Then V = qr^2 / 8 pi epsilon0 R^3

then if r = 0 then V = 0

am i correct here?

Show that the potential at distance r from the centre where r <R is given by V = q (3R^2 - r^2) / 8pi epsilon R^3

It looks like it has been integrated from r to (root 3) R. But i dont understand why??

Another problem is

A geiger counter has a metal cylinder of 2.10 dimater with a wire stretched along it's axis whose diamtere is 1.34 x 10^-4 cm in dimater. If 855 V is applied between these two what is the electric field at the surface of the wire and the cylinder??

lets say lambda = Q / L

then flux = EA = E 2 pi r L = 4 pi k Qenc = 4 pi k lambda L

so 2 k lambda / r = E

then i integrate because V = integrate E dr

so that V = 2k lambda Log r

But now i m stumped as to how to proceed please help!!

thanks a lot

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Help with electric potential!

**Physics Forums | Science Articles, Homework Help, Discussion**