Electric fields and net charge

  • Thread starter caljuice
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  • #1
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Main Question or Discussion Point

If a sphere has a net charge of zero, then it experiences no electric field right? But if you bring a + charged rod it, the electrons experience a field and all move towards it. But the net charge for the sphere is still zero since same number and electrons cancelling out. So do we say the electric field of the sphere is still zero when the electrons clearly experience a field?

Also if an charged object is in several electric fields, but the forces cancel out (static equilbrium), do we still say that object experiences an electric field?

Thanks.
 

Answers and Replies

  • #2
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The E field inside the sphere is still zero when placed in an external field , The induced surface charges will make it cancel inside . But the polarized conducting sphere will alter the E field outside . On your second question We would say it doesn't experience an E field, It would be like being inside a hollow spherical conducting charged sphere .
 
  • #3
If a sphere has a net charge of zero, then it experiences no electric field right? But if you bring a + charged rod it, the electrons experience a field and all move towards it. But the net charge for the sphere is still zero since same number and electrons cancelling out. So do we say the electric field of the sphere is still zero when the electrons clearly experience a field?

Also if an charged object is in several electric fields, but the forces cancel out (static equilbrium), do we still say that object experiences an electric field?

Thanks.
Charge is relative, not absolute.
 
  • #4
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Assuming that it's a conducting sphere, when you bring the positively charged rod near the sphere, negative charges will accumulate on the surface of the sphere facing toward the rod, and positive charges will accumulate on the surface of the sphere facing away from the rod. Outside the sphere but near it, on the side facing the rod, an electric field vector E will point toward the sphere, and on the side facing away from the rod an electric field vector will point away from the sphere.

Your phrase about whether the sphere "experiences an electric field" is unusual and I don't know what it means. Do you mean "experience a force" as a result of being in the place where there is a field? The charges within in the sphere do experience such a force, and that is why they have moved to the locations on the surface where they have moved to.
 

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