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*R*

_{1},

*R*

_{2}each carry a total charge

*Q*. What is the electric field between the two shells?

I don't know what kind of answer they are expecting. Do I just describe it? Here's my attempt:

The field lines from the inner shell will point away from the inner shell towards the outer shell. The field lines from the outer shell will point away from the outer shell towards the inner shell. Since the outer shell has the same total charge as the inner shell, but it is spread out more over the larger surface area, the point where the field lines meet will be closer to the outer shell.

[tex]\frac{{4\pi r_1^2 }}{{4\pi r_2^2 }} = \frac{{r_1^2 }}{{r_2^2 }}[/tex]

So the field lines from the inner sphere will be [tex]\frac{{r_1^2 }}{{r_2^2 }}[/tex]

stronger than from the outer sphere. So the distance is [tex]

\frac{{\frac{{r_1^2 }}{{r_2^2 }}}}{{1 + \left( {\frac{{r_1^2 }}{{r_2^2 }}} \right)}}

[/tex] times the distance between the spheres, closer to the outer sphere.

Is this right? Is this even the way I should express the answer?