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How does a solenoid work?

  1. Mar 27, 2012 #1
    I know an electromagnet can be created by wrapping a wire around a metal tube and putting some current across the wire. This creates a magnetic field. my question is why does the magnetic field decrease when the metal tube is removed leaving just the wire?
  2. jcsd
  3. Mar 28, 2012 #2


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    It depends upon what sort of solenoid you refer to.
    If the solenoid moves an armature inside the tube then you do not want a core of magnetic material as it will not help to increase the magnetic field affecting the magnetic armature. A non-magnetic tube (former) is just needed to maintain the shape of the coil.

    If your solenoid acts on an external armature then an Iron (ferromagnetic) core will increase the field considerably due to the increased Permeability. Non-magnetic metal like aluminium will make no difference.
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