To give an idea about the dielectric properties of metals, an experimental setup must be there for students. I am looking for an easy and cheaper set up to be installed in the lab.
Actually the two references cited above are identical. The attached file is good but does not respond to the question, which is rather philosophical: what is the dielectric property of a METAL, which is a conductor? If one looks at the complex impedance a piece of metal is well characterized by a resitor - without any capacitor. In fact, it is not possible to build a condenser if we put a consuctor between the capacitor plates, as there will be no BOUND charges, only mobile ones, therefore the charge will more form one electrode to the other. I wonder hat the theoreticla physicists tell about this problem. Is it possible to defien the dielectric porperty of metals???
The following application note can be helpful (page 17) :
http://www3.imperial.ac.uk/pls/portallive/docs/1/11949698.PDF
Actually the two references cited above are identical. The attached file is good but does not respond to the question, which is rather philosophical: what is the dielectric property of a METAL, which is a conductor? If one looks at the complex impedance a piece of metal is well characterized by a resitor - without any capacitor. In fact, it is not possible to build a condenser if we put a consuctor between the capacitor plates, as there will be no BOUND charges, only mobile ones, therefore the charge will more form one electrode to the other. I wonder hat the theoreticla physicists tell about this problem. Is it possible to defien the dielectric porperty of metals???
By defining the dielectric property I assume you mean the dielectric constant, which is related to the electromagnetic wave propagation in a material when a voltage is applied (due to polarization). To establish an electric field inside a material the electrons should not be mobilized by a potential difference (perfect dielectric material) at least they should resist to it to some degree so one can define a dielectric constant with respect to some reference such as the vacuum.
A metal or metal alloy system in its pure state has free electrons, in theory an electron cloud surrounding the core, that is, electrons are not bound to their parent atoms so tightly, they will not resist to move (look for fermi surfaces). Because of this the electric field inside a metal will be zero and moreover as there is no strict evidence that the acceleration of an electron has a limit, the metal theoretically can compansate all the energy applied to it. This results in a dielectric constant having an infinite value (of course this is valid only for a perfect conductor).
To be more simple to have a dielectric constant the material should be polarizable but a conductor (in this case a metal) cannot so theoretically it is not defined. BUT as far as I remember from what I read on dielectric constant approximations for metals, it is possibble but the result will be a complex number. The calculation is possible because considering a metal or any other material, there is no perfect conductor in nature due to the impurities, crystal defects and a number of other theoretical reasons.
That is all I can comment on the subject, if you want to go further in electrical/magnetic or optical properties of metals I suggest you to dig up condensed materials physics, to be more specific the theory of Fermi Surfaces (Levels).
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Material Characterization