- #1

Arman777

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## Homework Statement

A metallic sphere of radius a is placed concentrically with a metallic spherical shell with inner radius b and outer radius c. The sphere has a total charge of 2Q and the shell has a total charge of 3Q.

(a) What is the charge distribution? Specifically, what is the charge density in the interior of the metals and at each surface (at r = a, b and c)?

(b) Use Gauss’ law to ﬁnd the electric ﬁeld at every point.

## Homework Equations

Gaussian Law

## The Attempt at a Solution

[/B]Part (a) The charge density of the interior of A is ##ρ=\frac {3(2Q)} {4πa^3}## and for other sphere

##ρ=\frac {3(3Q)} {4π(c^3-b^3}##

The surfaces charge density should be zero.I think like that cause.Electrons cannot pass air.

Electric field will be zero inside the small sphere ##(E=0 , r<a)## then its ##E=\frac {2Q} {4πr^2}## , ##a<r<b## then again zero inside the outer sphere ##(E=0, b<r<c)## then its ##E=\frac {5Q} {4πr^2}## , ##c<r##

Is this true ?