Permanent Magnetic Field vs Electromagnetic Field












3














If I put a permanent magnet under a box and an energized electromagnetic coil under another box could you tell me which box was covering the permanent magnet? If the answer is yes what test would you use?
Note: The coil is receiving a steady dc current.






electromagnetism magnetic-fields







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    3














    If I put a permanent magnet under a box and an energized electromagnetic coil under another box could you tell me which box was covering the permanent magnet? If the answer is yes what test would you use?
    Note: The coil is receiving a steady dc current.






    electromagnetism magnetic-fields







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      3












      3








      3







      If I put a permanent magnet under a box and an energized electromagnetic coil under another box could you tell me which box was covering the permanent magnet? If the answer is yes what test would you use?
      Note: The coil is receiving a steady dc current.






      electromagnetism magnetic-fields







      share|cite|improve this question













      If I put a permanent magnet under a box and an energized electromagnetic coil under another box could you tell me which box was covering the permanent magnet? If the answer is yes what test would you use?
      Note: The coil is receiving a steady dc current.






      electromagnetism magnetic-fields




      electromagnetism magnetic-fields






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      share|cite|improve this question











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      asked 9 hours ago









      LambdaLambda

      2,49641125




      2,49641125






















          6 Answers
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          active

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          5














          If this is a normal coil wound with resistance wire, then around the coil with current will be the electric field and magnetic field, and around the permanent magnet only magnetic field. If the boxes do not shield the electric field, it will not be difficult to detect the coil with current by measuring the electric field.






          share|cite|improve this answer





















          • there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
            – anna v
            7 hours ago










          • @annav Thank you, I have it.
            – Alex Trounev
            7 hours ago










          • @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
            – Lambda
            3 hours ago



















          5














          The box containing the coil will heat up more and more due to the joule effect. So measuring the temperature you could tell.






          share|cite|improve this answer





























            3














            Warm it up near or beyond the Curie temperature, it will make no difference to the coil but the "permanent" becomes "impermanent".






            share|cite|improve this answer





























              2














              If the permanent magnet and the electromagnet are shaped so that the field in the box has precisely the same shape, there is no way to know which box covers which magnet, simply by measuring the field using a tiny probe magnet or tiny probe coil with very small current.



              However, it may be possible to distinguish between the two cases by a more "intrusive" measurement: A metal detector, for example, would very likely respond slightly differently for one than the other. The electromagnet coil would act as a transformer secondary if driven by an electromagnet above the box, and should behave in a slightly different way than the permanent magnet.



              Edited for clarity: "Driven" means, in this context, that the electromagnet above the box is energized by a time-varying current, which will produce a time-varying field, which in turn will "drive" a time-varying additional EMF in the coil below the box.






              share|cite|improve this answer























              • Transformers do not work for DC.
                – my2cts
                8 hours ago










              • I guess "driven" needs to be clarified.
                – S. McGrew
                8 hours ago



















              1














              With an x-ray snapshot you should be able to see the difference :). However the magnetic fields can be made to be indistinguishable within certain intensity limits. There is a limit to what a permanent magnet can achieve in a certain volume. An electromagnet can produce a much stronger field.



              See https://hypertextbook.com/facts/2000/AnnaWoo.shtml .






              share|cite|improve this answer























              • That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                – Sparky256
                4 hours ago












              • Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                – my2cts
                3 hours ago










              • @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                – cmaster
                2 hours ago



















              0














              Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast. Oddly enough the same intense magnetic pulse is used to magnetize neodymium-iron-born magnets.



              For a study-state magnetic field (not superconducting) NIB alloys have the strongest field for now. Some NIB alloys will tolerate intense heat at the cost of total field strength.






              share|cite








              New contributor




              Sparky256 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
              Check out our Code of Conduct.


















              • This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                – cmaster
                2 hours ago










              • @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                – Sparky256
                1 hour ago











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              6 Answers
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              active

              oldest

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              6 Answers
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              active

              oldest

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              active

              oldest

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              active

              oldest

              votes









              5














              If this is a normal coil wound with resistance wire, then around the coil with current will be the electric field and magnetic field, and around the permanent magnet only magnetic field. If the boxes do not shield the electric field, it will not be difficult to detect the coil with current by measuring the electric field.






              share|cite|improve this answer





















              • there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
                – anna v
                7 hours ago










              • @annav Thank you, I have it.
                – Alex Trounev
                7 hours ago










              • @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
                – Lambda
                3 hours ago
















              5














              If this is a normal coil wound with resistance wire, then around the coil with current will be the electric field and magnetic field, and around the permanent magnet only magnetic field. If the boxes do not shield the electric field, it will not be difficult to detect the coil with current by measuring the electric field.






              share|cite|improve this answer





















              • there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
                – anna v
                7 hours ago










              • @annav Thank you, I have it.
                – Alex Trounev
                7 hours ago










              • @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
                – Lambda
                3 hours ago














              5












              5








              5






              If this is a normal coil wound with resistance wire, then around the coil with current will be the electric field and magnetic field, and around the permanent magnet only magnetic field. If the boxes do not shield the electric field, it will not be difficult to detect the coil with current by measuring the electric field.






              share|cite|improve this answer












              If this is a normal coil wound with resistance wire, then around the coil with current will be the electric field and magnetic field, and around the permanent magnet only magnetic field. If the boxes do not shield the electric field, it will not be difficult to detect the coil with current by measuring the electric field.







              share|cite|improve this answer












              share|cite|improve this answer



              share|cite|improve this answer










              answered 7 hours ago









              Alex TrounevAlex Trounev

              28215




              28215












              • there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
                – anna v
                7 hours ago










              • @annav Thank you, I have it.
                – Alex Trounev
                7 hours ago










              • @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
                – Lambda
                3 hours ago


















              • there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
                – anna v
                7 hours ago










              • @annav Thank you, I have it.
                – Alex Trounev
                7 hours ago










              • @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
                – Lambda
                3 hours ago
















              there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
              – anna v
              7 hours ago




              there are "non contact voltage testers" on the market.amazon.com/Voltage-Detector-Non-Contact-Electric-12~220V/dp/… . Here is a report on DC testers e-reports-ext.llnl.gov/pdf/374701.pdf
              – anna v
              7 hours ago












              @annav Thank you, I have it.
              – Alex Trounev
              7 hours ago




              @annav Thank you, I have it.
              – Alex Trounev
              7 hours ago












              @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
              – Lambda
              3 hours ago




              @annav Thanks for posting the links. I am wondering if the probes wouldn’t also measure the magnetic field.
              – Lambda
              3 hours ago











              5














              The box containing the coil will heat up more and more due to the joule effect. So measuring the temperature you could tell.






              share|cite|improve this answer


























                5














                The box containing the coil will heat up more and more due to the joule effect. So measuring the temperature you could tell.






                share|cite|improve this answer
























                  5












                  5








                  5






                  The box containing the coil will heat up more and more due to the joule effect. So measuring the temperature you could tell.






                  share|cite|improve this answer












                  The box containing the coil will heat up more and more due to the joule effect. So measuring the temperature you could tell.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered 7 hours ago









                  Run like hellRun like hell

                  1,193724




                  1,193724























                      3














                      Warm it up near or beyond the Curie temperature, it will make no difference to the coil but the "permanent" becomes "impermanent".






                      share|cite|improve this answer


























                        3














                        Warm it up near or beyond the Curie temperature, it will make no difference to the coil but the "permanent" becomes "impermanent".






                        share|cite|improve this answer
























                          3












                          3








                          3






                          Warm it up near or beyond the Curie temperature, it will make no difference to the coil but the "permanent" becomes "impermanent".






                          share|cite|improve this answer












                          Warm it up near or beyond the Curie temperature, it will make no difference to the coil but the "permanent" becomes "impermanent".







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 7 hours ago









                          hyportnexhyportnex

                          4,2871824




                          4,2871824























                              2














                              If the permanent magnet and the electromagnet are shaped so that the field in the box has precisely the same shape, there is no way to know which box covers which magnet, simply by measuring the field using a tiny probe magnet or tiny probe coil with very small current.



                              However, it may be possible to distinguish between the two cases by a more "intrusive" measurement: A metal detector, for example, would very likely respond slightly differently for one than the other. The electromagnet coil would act as a transformer secondary if driven by an electromagnet above the box, and should behave in a slightly different way than the permanent magnet.



                              Edited for clarity: "Driven" means, in this context, that the electromagnet above the box is energized by a time-varying current, which will produce a time-varying field, which in turn will "drive" a time-varying additional EMF in the coil below the box.






                              share|cite|improve this answer























                              • Transformers do not work for DC.
                                – my2cts
                                8 hours ago










                              • I guess "driven" needs to be clarified.
                                – S. McGrew
                                8 hours ago
















                              2














                              If the permanent magnet and the electromagnet are shaped so that the field in the box has precisely the same shape, there is no way to know which box covers which magnet, simply by measuring the field using a tiny probe magnet or tiny probe coil with very small current.



                              However, it may be possible to distinguish between the two cases by a more "intrusive" measurement: A metal detector, for example, would very likely respond slightly differently for one than the other. The electromagnet coil would act as a transformer secondary if driven by an electromagnet above the box, and should behave in a slightly different way than the permanent magnet.



                              Edited for clarity: "Driven" means, in this context, that the electromagnet above the box is energized by a time-varying current, which will produce a time-varying field, which in turn will "drive" a time-varying additional EMF in the coil below the box.






                              share|cite|improve this answer























                              • Transformers do not work for DC.
                                – my2cts
                                8 hours ago










                              • I guess "driven" needs to be clarified.
                                – S. McGrew
                                8 hours ago














                              2












                              2








                              2






                              If the permanent magnet and the electromagnet are shaped so that the field in the box has precisely the same shape, there is no way to know which box covers which magnet, simply by measuring the field using a tiny probe magnet or tiny probe coil with very small current.



                              However, it may be possible to distinguish between the two cases by a more "intrusive" measurement: A metal detector, for example, would very likely respond slightly differently for one than the other. The electromagnet coil would act as a transformer secondary if driven by an electromagnet above the box, and should behave in a slightly different way than the permanent magnet.



                              Edited for clarity: "Driven" means, in this context, that the electromagnet above the box is energized by a time-varying current, which will produce a time-varying field, which in turn will "drive" a time-varying additional EMF in the coil below the box.






                              share|cite|improve this answer














                              If the permanent magnet and the electromagnet are shaped so that the field in the box has precisely the same shape, there is no way to know which box covers which magnet, simply by measuring the field using a tiny probe magnet or tiny probe coil with very small current.



                              However, it may be possible to distinguish between the two cases by a more "intrusive" measurement: A metal detector, for example, would very likely respond slightly differently for one than the other. The electromagnet coil would act as a transformer secondary if driven by an electromagnet above the box, and should behave in a slightly different way than the permanent magnet.



                              Edited for clarity: "Driven" means, in this context, that the electromagnet above the box is energized by a time-varying current, which will produce a time-varying field, which in turn will "drive" a time-varying additional EMF in the coil below the box.







                              share|cite|improve this answer














                              share|cite|improve this answer



                              share|cite|improve this answer








                              edited 8 hours ago

























                              answered 8 hours ago









                              S. McGrewS. McGrew

                              7,07721130




                              7,07721130












                              • Transformers do not work for DC.
                                – my2cts
                                8 hours ago










                              • I guess "driven" needs to be clarified.
                                – S. McGrew
                                8 hours ago


















                              • Transformers do not work for DC.
                                – my2cts
                                8 hours ago










                              • I guess "driven" needs to be clarified.
                                – S. McGrew
                                8 hours ago
















                              Transformers do not work for DC.
                              – my2cts
                              8 hours ago




                              Transformers do not work for DC.
                              – my2cts
                              8 hours ago












                              I guess "driven" needs to be clarified.
                              – S. McGrew
                              8 hours ago




                              I guess "driven" needs to be clarified.
                              – S. McGrew
                              8 hours ago











                              1














                              With an x-ray snapshot you should be able to see the difference :). However the magnetic fields can be made to be indistinguishable within certain intensity limits. There is a limit to what a permanent magnet can achieve in a certain volume. An electromagnet can produce a much stronger field.



                              See https://hypertextbook.com/facts/2000/AnnaWoo.shtml .






                              share|cite|improve this answer























                              • That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                                – Sparky256
                                4 hours ago












                              • Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                                – my2cts
                                3 hours ago










                              • @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                                – cmaster
                                2 hours ago
















                              1














                              With an x-ray snapshot you should be able to see the difference :). However the magnetic fields can be made to be indistinguishable within certain intensity limits. There is a limit to what a permanent magnet can achieve in a certain volume. An electromagnet can produce a much stronger field.



                              See https://hypertextbook.com/facts/2000/AnnaWoo.shtml .






                              share|cite|improve this answer























                              • That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                                – Sparky256
                                4 hours ago












                              • Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                                – my2cts
                                3 hours ago










                              • @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                                – cmaster
                                2 hours ago














                              1












                              1








                              1






                              With an x-ray snapshot you should be able to see the difference :). However the magnetic fields can be made to be indistinguishable within certain intensity limits. There is a limit to what a permanent magnet can achieve in a certain volume. An electromagnet can produce a much stronger field.



                              See https://hypertextbook.com/facts/2000/AnnaWoo.shtml .






                              share|cite|improve this answer














                              With an x-ray snapshot you should be able to see the difference :). However the magnetic fields can be made to be indistinguishable within certain intensity limits. There is a limit to what a permanent magnet can achieve in a certain volume. An electromagnet can produce a much stronger field.



                              See https://hypertextbook.com/facts/2000/AnnaWoo.shtml .







                              share|cite|improve this answer














                              share|cite|improve this answer



                              share|cite|improve this answer








                              edited 8 hours ago

























                              answered 8 hours ago









                              my2ctsmy2cts

                              4,7172618




                              4,7172618












                              • That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                                – Sparky256
                                4 hours ago












                              • Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                                – my2cts
                                3 hours ago










                              • @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                                – cmaster
                                2 hours ago


















                              • That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                                – Sparky256
                                4 hours ago












                              • Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                                – my2cts
                                3 hours ago










                              • @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                                – cmaster
                                2 hours ago
















                              That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                              – Sparky256
                              4 hours ago






                              That answer is wrong. Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast.
                              – Sparky256
                              4 hours ago














                              Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                              – my2cts
                              3 hours ago




                              Are you saying that the information in th elink is wrong? It states that the strongest permanent field is 0.1 T, much less that that of a steady state electromagnet. Do you have a reference for your statement?
                              – my2cts
                              3 hours ago












                              @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                              – cmaster
                              2 hours ago




                              @Sparky256 Btw: some electromagnets can exceed 10T. Obviously continuously, as they are superconducting. Here is a link: home.cern/news/news/engineering/…
                              – cmaster
                              2 hours ago











                              0














                              Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast. Oddly enough the same intense magnetic pulse is used to magnetize neodymium-iron-born magnets.



                              For a study-state magnetic field (not superconducting) NIB alloys have the strongest field for now. Some NIB alloys will tolerate intense heat at the cost of total field strength.






                              share|cite








                              New contributor




                              Sparky256 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                              Check out our Code of Conduct.


















                              • This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                                – cmaster
                                2 hours ago










                              • @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                                – Sparky256
                                1 hour ago
















                              0














                              Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast. Oddly enough the same intense magnetic pulse is used to magnetize neodymium-iron-born magnets.



                              For a study-state magnetic field (not superconducting) NIB alloys have the strongest field for now. Some NIB alloys will tolerate intense heat at the cost of total field strength.






                              share|cite








                              New contributor




                              Sparky256 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                              Check out our Code of Conduct.


















                              • This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                                – cmaster
                                2 hours ago










                              • @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                                – Sparky256
                                1 hour ago














                              0












                              0








                              0






                              Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast. Oddly enough the same intense magnetic pulse is used to magnetize neodymium-iron-born magnets.



                              For a study-state magnetic field (not superconducting) NIB alloys have the strongest field for now. Some NIB alloys will tolerate intense heat at the cost of total field strength.






                              share|cite








                              New contributor




                              Sparky256 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                              Check out our Code of Conduct.









                              Electromagnets can produce a stronger pulsed field, but not a study state field as the windings would burn up fast. Oddly enough the same intense magnetic pulse is used to magnetize neodymium-iron-born magnets.



                              For a study-state magnetic field (not superconducting) NIB alloys have the strongest field for now. Some NIB alloys will tolerate intense heat at the cost of total field strength.







                              share|cite








                              New contributor




                              Sparky256 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                              Check out our Code of Conduct.









                              share|cite



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                              answered 4 hours ago









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                              • This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                                – cmaster
                                2 hours ago










                              • @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                                – Sparky256
                                1 hour ago


















                              • This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                                – cmaster
                                2 hours ago










                              • @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                                – Sparky256
                                1 hour ago
















                              This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                              – cmaster
                              2 hours ago




                              This heavily depends on the coil material, and, perchance, the cooling. Superconducting magnets don't have any issue delivering extremely strong magnetic fields continuously, and they obviously classify as electromagnets...
                              – cmaster
                              2 hours ago












                              @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                              – Sparky256
                              1 hour ago




                              @cmaster. I am aware of superconducting magnets, which can also transfer DC power as a superconducting transformer. Superconducting was not part of the OP's question, so it is not part of any answers. It would have to be posted as a separate question.
                              – Sparky256
                              1 hour ago


















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