Why is there an induced EMF in a plastic ring?












4














If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal thus allowing it to collect together and form charged sides. However, plastic is an insulator so how can it have it's charges moving? It's even mentioned in the answers that due to the insulating nature of plastic no current will flow, but then how do the charges separate in the first place?



If it helps, I typically think of the Loretnz force acting on charges for electromagnetic induction.



Also with this induced emf, would there be a difference in magnitude of the emf between the metal and plastic ring?






electromagnetism electric-current voltage electromagnetic-induction







share|cite|improve this question





























    4














    If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal thus allowing it to collect together and form charged sides. However, plastic is an insulator so how can it have it's charges moving? It's even mentioned in the answers that due to the insulating nature of plastic no current will flow, but then how do the charges separate in the first place?



    If it helps, I typically think of the Loretnz force acting on charges for electromagnetic induction.



    Also with this induced emf, would there be a difference in magnitude of the emf between the metal and plastic ring?






    electromagnetism electric-current voltage electromagnetic-induction







    share|cite|improve this question



























      4












      4








      4







      If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal thus allowing it to collect together and form charged sides. However, plastic is an insulator so how can it have it's charges moving? It's even mentioned in the answers that due to the insulating nature of plastic no current will flow, but then how do the charges separate in the first place?



      If it helps, I typically think of the Loretnz force acting on charges for electromagnetic induction.



      Also with this induced emf, would there be a difference in magnitude of the emf between the metal and plastic ring?






      electromagnetism electric-current voltage electromagnetic-induction







      share|cite|improve this question















      If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal thus allowing it to collect together and form charged sides. However, plastic is an insulator so how can it have it's charges moving? It's even mentioned in the answers that due to the insulating nature of plastic no current will flow, but then how do the charges separate in the first place?



      If it helps, I typically think of the Loretnz force acting on charges for electromagnetic induction.



      Also with this induced emf, would there be a difference in magnitude of the emf between the metal and plastic ring?






      electromagnetism electric-current voltage electromagnetic-induction




      electromagnetism electric-current voltage electromagnetic-induction






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited 51 secs ago









      Qmechanic♦

      101k121831149




      101k121831149










      asked 2 hours ago









      John Hon

      321210




      321210






















          3 Answers
          3






          active

          oldest

          votes


















          2














          An electromotive force doesn't require a conductor --- it doesn't even require matter. The electromagnetic field is a local property of the vacuum, governed by Maxwell's equations. The relevant one in this case is



          $$
          vecnabla times vec E = -fracpartial{partial t}vec B
          $$



          That is, at any point in space, a changing magnitude or direction for the magnetic field is inextricably associated with an electric field with nonzero curl.
          Because electromagnetism obeys all the symmetries of special relativity, it doesn't matter whether the point of interest is stationary and the field there is changing, or if the point of interest is moving through a region of static but nonuniform magnetic fields.



          Now, a "conductor" is some material with the property of "always" having $vec E=0$ inside. Since the changing magnetic field is associated with $vec E neq 0$, then the charges in the conductor where $partialvec B/partial t neq 0$ must move to produce $vec E=0$ by superposition. You can think of that as motion due to the Lorentz force if you like. The Lorentz force,



          $$
          vec F = qleft(vec vtimesvec B + vec E right),
          $$



          implies that a charge must be moving to experience a force from a static magnetic field. However a changing magnetic field produces a nonzero $vec E$, and can therefore exert force on stationary charges.






          share|cite|improve this answer





















          • This is the correct answer. The question confuses emf and current, I think.
            – Jerry Schirmer
            21 mins ago



















          0














          Something is very funny here. "Why does an emf form?"
          As far as I understand physics it doesn't. And shouldn't
          "thus allowing it to collect together and form charged sides"
          This seems to describe something like the amber rod rubbed with wool. Only there you can have charges accumulating. Not in a metal.






          share|cite|improve this answer





























            0














            The electron shells of atoms get distorted ie move a small amount relative to the nuclei, so that electric dipoles are induced.






            share|cite|improve this answer





















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              3 Answers
              3






              active

              oldest

              votes








              3 Answers
              3






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              2














              An electromotive force doesn't require a conductor --- it doesn't even require matter. The electromagnetic field is a local property of the vacuum, governed by Maxwell's equations. The relevant one in this case is



              $$
              vecnabla times vec E = -fracpartial{partial t}vec B
              $$



              That is, at any point in space, a changing magnitude or direction for the magnetic field is inextricably associated with an electric field with nonzero curl.
              Because electromagnetism obeys all the symmetries of special relativity, it doesn't matter whether the point of interest is stationary and the field there is changing, or if the point of interest is moving through a region of static but nonuniform magnetic fields.



              Now, a "conductor" is some material with the property of "always" having $vec E=0$ inside. Since the changing magnetic field is associated with $vec E neq 0$, then the charges in the conductor where $partialvec B/partial t neq 0$ must move to produce $vec E=0$ by superposition. You can think of that as motion due to the Lorentz force if you like. The Lorentz force,



              $$
              vec F = qleft(vec vtimesvec B + vec E right),
              $$



              implies that a charge must be moving to experience a force from a static magnetic field. However a changing magnetic field produces a nonzero $vec E$, and can therefore exert force on stationary charges.






              share|cite|improve this answer





















              • This is the correct answer. The question confuses emf and current, I think.
                – Jerry Schirmer
                21 mins ago
















              2














              An electromotive force doesn't require a conductor --- it doesn't even require matter. The electromagnetic field is a local property of the vacuum, governed by Maxwell's equations. The relevant one in this case is



              $$
              vecnabla times vec E = -fracpartial{partial t}vec B
              $$



              That is, at any point in space, a changing magnitude or direction for the magnetic field is inextricably associated with an electric field with nonzero curl.
              Because electromagnetism obeys all the symmetries of special relativity, it doesn't matter whether the point of interest is stationary and the field there is changing, or if the point of interest is moving through a region of static but nonuniform magnetic fields.



              Now, a "conductor" is some material with the property of "always" having $vec E=0$ inside. Since the changing magnetic field is associated with $vec E neq 0$, then the charges in the conductor where $partialvec B/partial t neq 0$ must move to produce $vec E=0$ by superposition. You can think of that as motion due to the Lorentz force if you like. The Lorentz force,



              $$
              vec F = qleft(vec vtimesvec B + vec E right),
              $$



              implies that a charge must be moving to experience a force from a static magnetic field. However a changing magnetic field produces a nonzero $vec E$, and can therefore exert force on stationary charges.






              share|cite|improve this answer





















              • This is the correct answer. The question confuses emf and current, I think.
                – Jerry Schirmer
                21 mins ago














              2












              2








              2






              An electromotive force doesn't require a conductor --- it doesn't even require matter. The electromagnetic field is a local property of the vacuum, governed by Maxwell's equations. The relevant one in this case is



              $$
              vecnabla times vec E = -fracpartial{partial t}vec B
              $$



              That is, at any point in space, a changing magnitude or direction for the magnetic field is inextricably associated with an electric field with nonzero curl.
              Because electromagnetism obeys all the symmetries of special relativity, it doesn't matter whether the point of interest is stationary and the field there is changing, or if the point of interest is moving through a region of static but nonuniform magnetic fields.



              Now, a "conductor" is some material with the property of "always" having $vec E=0$ inside. Since the changing magnetic field is associated with $vec E neq 0$, then the charges in the conductor where $partialvec B/partial t neq 0$ must move to produce $vec E=0$ by superposition. You can think of that as motion due to the Lorentz force if you like. The Lorentz force,



              $$
              vec F = qleft(vec vtimesvec B + vec E right),
              $$



              implies that a charge must be moving to experience a force from a static magnetic field. However a changing magnetic field produces a nonzero $vec E$, and can therefore exert force on stationary charges.






              share|cite|improve this answer












              An electromotive force doesn't require a conductor --- it doesn't even require matter. The electromagnetic field is a local property of the vacuum, governed by Maxwell's equations. The relevant one in this case is



              $$
              vecnabla times vec E = -fracpartial{partial t}vec B
              $$



              That is, at any point in space, a changing magnitude or direction for the magnetic field is inextricably associated with an electric field with nonzero curl.
              Because electromagnetism obeys all the symmetries of special relativity, it doesn't matter whether the point of interest is stationary and the field there is changing, or if the point of interest is moving through a region of static but nonuniform magnetic fields.



              Now, a "conductor" is some material with the property of "always" having $vec E=0$ inside. Since the changing magnetic field is associated with $vec E neq 0$, then the charges in the conductor where $partialvec B/partial t neq 0$ must move to produce $vec E=0$ by superposition. You can think of that as motion due to the Lorentz force if you like. The Lorentz force,



              $$
              vec F = qleft(vec vtimesvec B + vec E right),
              $$



              implies that a charge must be moving to experience a force from a static magnetic field. However a changing magnetic field produces a nonzero $vec E$, and can therefore exert force on stationary charges.







              share|cite|improve this answer












              share|cite|improve this answer



              share|cite|improve this answer










              answered 30 mins ago









              rob♦

              39.1k971161




              39.1k971161












              • This is the correct answer. The question confuses emf and current, I think.
                – Jerry Schirmer
                21 mins ago


















              • This is the correct answer. The question confuses emf and current, I think.
                – Jerry Schirmer
                21 mins ago
















              This is the correct answer. The question confuses emf and current, I think.
              – Jerry Schirmer
              21 mins ago




              This is the correct answer. The question confuses emf and current, I think.
              – Jerry Schirmer
              21 mins ago











              0














              Something is very funny here. "Why does an emf form?"
              As far as I understand physics it doesn't. And shouldn't
              "thus allowing it to collect together and form charged sides"
              This seems to describe something like the amber rod rubbed with wool. Only there you can have charges accumulating. Not in a metal.






              share|cite|improve this answer


























                0














                Something is very funny here. "Why does an emf form?"
                As far as I understand physics it doesn't. And shouldn't
                "thus allowing it to collect together and form charged sides"
                This seems to describe something like the amber rod rubbed with wool. Only there you can have charges accumulating. Not in a metal.






                share|cite|improve this answer
























                  0












                  0








                  0






                  Something is very funny here. "Why does an emf form?"
                  As far as I understand physics it doesn't. And shouldn't
                  "thus allowing it to collect together and form charged sides"
                  This seems to describe something like the amber rod rubbed with wool. Only there you can have charges accumulating. Not in a metal.






                  share|cite|improve this answer












                  Something is very funny here. "Why does an emf form?"
                  As far as I understand physics it doesn't. And shouldn't
                  "thus allowing it to collect together and form charged sides"
                  This seems to describe something like the amber rod rubbed with wool. Only there you can have charges accumulating. Not in a metal.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered 1 hour ago









                  Dr S T Lakshmikumar

                  212




                  212























                      0














                      The electron shells of atoms get distorted ie move a small amount relative to the nuclei, so that electric dipoles are induced.






                      share|cite|improve this answer


























                        0














                        The electron shells of atoms get distorted ie move a small amount relative to the nuclei, so that electric dipoles are induced.






                        share|cite|improve this answer
























                          0












                          0








                          0






                          The electron shells of atoms get distorted ie move a small amount relative to the nuclei, so that electric dipoles are induced.






                          share|cite|improve this answer












                          The electron shells of atoms get distorted ie move a small amount relative to the nuclei, so that electric dipoles are induced.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 1 hour ago









                          Farcher

                          47.3k33696




                          47.3k33696






























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