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B Do electromagnets exhibit the same properties of a permanent

  1. Aug 16, 2016 #1
    I am just curious whether the formulas that apply to 'magnets', such as the formula for the magnetic field of a dipole (as brought up in my previous thread), apply to both electromagnets and permanent magnets, and other types? Is the magnetic fields exhibited by these different forms of magnetism the same?
     
  2. jcsd
  3. Aug 16, 2016 #2

    Charles Link

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    The magnetic fields for a permanent magnet and an electromagnet are essentially the same. The maximum magnetic field strengths that they have are about the same for both also, but will differ from one material to another=basically in the neighborhood of B=1.0-2.0 Webers/m^2. The electromagnets have the advantage that in many cases these materials can make good transformers where the applied magnetic field from the current in the solenoid is alternating at 60 Hz (actually reversing direction completely at a rate of 60 Hz (60 cycles per second)) and the magnetization follows the applied field in an almost linear fashion. A high quality permanent magnet can not be made to switch back an forth like that. In fact, it is generally quite difficult to reverse the polarity of a good permanent magnet even once with the magnetic field from a solenoid. It takes a very powerful solenoid (very high DC currents) to overcome the field of the permanent magnet and reverse its magnetization. Once the magnetization of a permanent magnet is reversed, the same strong solenoid current in the other direction would be needed to return the permanent magnet to its original state.
     
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