Induced charge on a solid metal sphere

[luhar]

All

I understand clearly that if a metal sphere is charged then the charges must reside on the surface because that is the only way there is no electric field within the metal. However if you imagine a neutral metal sphere, and let's say it is suddenly enclosed by a uniformly charged metal shell concentric with the neutral sphere (radium of shell greater than sphere). In this case will it induce charges on the surface of the neutral sphere? I cannot see how it would since if it does then these would have to reside on the sphere's surface and then the remaining charge of opposite polarity on the sphere would have no place to go! If that is true then it it is a little strange that despite the presence of an electric field on the surface of the sphere (due to the presence of the charged shell) and the free electrons within it nothing happens!

 

[cwilkins]

I suspect that either nothing will happen, or there will be a layer on top that is negatively charged, followed by a layer immediately below (on atomic scales) that is positively charged. The configuration will somehow adjust itself so that there is no field inside the bulk of sphere. (Note: I could be completely wrong.)

[Motivating source: Jackson's Classical Electrodynamics, section "Some Remarks on Idealizations in Electromagnetism"]

 

[Naty1]

no. no. [I was required to submit a least four characters...]

 

[Meir Achuz]

All
enclosed by a uniformly charged metal shell concentric with the neutral sphere

There is no E field inside a charged metal shell, so nothing will happen to the enclosed sphere.

 

[sardar]

I can confirm that the induction of charges on the surface of a neutral metal sphere in the scenario described is indeed possible. This is due to the redistribution of charges within the metal sphere in response to the external electric field created by the charged shell.

When the charged shell is placed around the neutral metal sphere, the electric field lines from the shell will penetrate the surface of the sphere and reach the interior. This will cause the free electrons within the metal to redistribute themselves in a way that creates an equal and opposite electric field within the sphere, canceling out the external field. This redistribution of charges will result in a slight excess of charges on the surface of the sphere, creating a net induced charge.

It may seem strange that despite the presence of an external electric field and free electrons within the sphere, the charges on the surface do not simply flow to the opposite side. However, this is due to the fact that metals are good conductors and the charges are able to redistribute themselves quickly to create a balanced electric field within the sphere.

In summary, the induced charge on the surface of a neutral metal sphere in the presence of an external electric field is a result of the redistribution of charges within the metal, and does not contradict the fact that there is no electric field within the metal. This phenomenon is well understood and has been observed in many experiments.