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## Homework Statement

A hollow spherical shell (B) with inner radius R2 and esternal radius R3 is negatively charged with Q.

A spherical conducter (A) with radius R1 is placed within the the shell. A is charged with Q.

The centers of both shells coincide.

Then a negative point charge q is placed at R3.

Tasks:

1. Calculate the electric field genrated by the spheres at any point.

2. Calculate the force on the charge q

3.Calculate the work done by an external agent to bring q to infinity

2. Homework Equations

2. Homework Equations

Gauß-Law

## The Attempt at a Solution

(Non-native English speaker here but my lectures are in English so excuse any grammar or spelling mistakes, ok?)

First of all I tried to imagine how the charges on the spherical shell would redistribute.

The positive charge Q on the surface of A can't exactly escape so it has to stay there^^

I then thought that the charge -Q of B would arange along R2 on the inner surface of the shell.

Then there is no charge left on the outside surface of B.

So the object is seen as neutral when looked at from a distance r>R3, or isn't it?

1. According to Gauß law there is no E-field at a distance r<R1 since no charge is enclosed.

At R2<r<R1 the E-field should be

equal to ## \frac{1}{4\pi\epsilon}*\frac{Q}{r^2} ##

At r<R2 I think I can use the super position principle, adding the E-Field of both spheres

but since the charges have the same value (one negative one positive)

My E-field should be zero here....

but if this is true I don't get the second question...

since the force should be ## F=E*q ##

and the Field is equal to zero at R3 the force should be zero as well?

I really don't understand this task so please help....