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Capacitors don't require a dielectric material they?

  1. Mar 9, 2014 #1
    capacitors don't require a "dielectric" material they?

    whenever i hear about capacitors, i hear about the 'dielectric' material, but a dielectric material as opposed to a non-dielectric insulator just means that the material is polarizable. but polarizability only affects the field strength within the insulating material it doesn't really affect the externally applied E-field coming out the other end. what does affect the E-field coming out the other end is the relative permitivity constant, which can be obtained from any non-dielectric insulator right?
  2. jcsd
  3. Mar 9, 2014 #2
    What is a "non-dielectric insulator"? Do you have an example?
    And what is the "electric field coming out the other end"? The other end of what?
  4. Mar 9, 2014 #3
    can't think of any examples, i'm actually new to the whole distinction between dielectrics and insulators.. so i thought that insulating materials consisted of a spectrum, with one end of the spectrum being non-dielectric (non-polarizable) materials, and dielectric (or, easily polarizable) materials on the other end of the spectrum. is this view incorrect? if so can you give me a clearer picture of the distinction/relationship between dielectrics and insulators?

    referring to the electric field going into the insulator material and coming out of it on the opposite end from which it entered
  5. Mar 9, 2014 #4


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    Staff: Mentor

    You can have a capacitor with vacuum between the plates, in principle. Air is a fairly good approximation to a vacuum in this context, for relatively low electric fields inside the capacitor.
  6. Mar 10, 2014 #5
    I still think you are miss-understanding something.
    Some materials can be polarized more than others, this is true.
    And is measured by the dielectric constant (or by permitivity). What would you expect the permitivity of a "non-dielectric" to be?

    You may consider vacuum as an insulator which is not polarizable (see Jtbell's post) but I don't see the use.
    Have you seen the term "non-dielectric" in a book or paper?
    All materials made from atoms can be polarised in electric fields because the atoms can be.
    If the polarization is small they have a small dielectric constant but I don't think they are called "non-dielectrics". Air has a pretty small dielectric constant, almost close to 1, but it's still a dielectric, isn't it?

    The effect you are talking about in capacitors is produced by polarisation of the material between the plates. The polarization field reduces the field between the plates and so the voltage. The effect is increased capacitance.
    A material without polarization (assuming it exist) will do nothing for this.
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