Calculating Electric Potential at Sphere and Shell

[jromega3]

Homework Statement

A conducting sphere with radius a = 0.31 m has a net charge Qa = +4 µC. A thin, non-conducting spherical shell of radius b = 0.86 m surrounds the sphere and is concentric with it. This shell has a net charge Qb = +1.5 µC distributed uniformly over its surface. The electric potential at infinity is zero.

(a) Calculate the electric potential at a radial distance of 0.4 m outside of the thin shell.
(b) Calculate the potential at the thin shell.
(c) Find the electric potential mid-way between the surface of the sphere and the surrounding shell.
(d) Find the potential at the surface of the sphere.
(e) Find the potential at the center of the sphere.

Homework Equations

The Attempt at a Solution

These are driving me crazy. My work gives me the following answers...
a) 9*10^9 (4*10^-6+1.5*10^-6/1.57)
b) 9*10^9(4*10^-6+1.5*10^-6/0.215)
c) 9*10^9(4*10^-6/0.585+1.5*10^-6/0.86)
d) 9*10^9(4*10^-6/0.31+1.5*10^-6/0.86)
e) 9*10^9(4*10^-6/0.31+1.5*10^-6)

which aren't right when I'm typing them in.

 

[LowlyPion]

What is Gauss Law?
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/gaulaw.html#c2

 

[thomate1]

As a scientist, it is important to double-check your calculations and make sure your units are correct. It appears that your calculations may be correct, but your units may be causing issues when you are inputting them into the system. Make sure to use the correct units for charge (Coulombs) and distance (meters) when solving for electric potential. Additionally, it is important to note that the electric potential at infinity is zero, so you can use that information to check your solutions. If you are still having trouble, it may be helpful to review the equations and units for calculating electric potential.