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Material properties

Posted 08.12.2011, 06:11 GMT-5 MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 4.2 3 Replies

Jürgen Gluch
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Hello

today I noticed that my material copper has the properties "Electric conductivity | sigma | 5.998[S/m]" and "Reference resitivity | rho0 |1.72e8[Ohm*m]" as well as the temperature coefficient alpha. Why two values, because sigma = 1/rho0 , isn't it?
How can I check which physics uses which value, or how can I assign sigma = 1/rho0*(1+alpha*DeltaT)?

greetings
Jürgen Gluch
3 Replies Last Post 14.12.2011, 09:01 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 09.12.2011, 01:02 GMT-5
Hi

in V4 you have the "vue" for the active properties, and then you need to go through the equations in detail to see where and when some are used (tedious) mostly the doc covers this too, but the info is scattered around ;)

--
Good luck
Ivar
Hi in V4 you have the "vue" for the active properties, and then you need to go through the equations in detail to see where and when some are used (tedious) mostly the doc covers this too, but the info is scattered around ;) -- Good luck Ivar
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago 09.12.2011, 03:07 GMT-5
Hi,

The reference resistivity rho0 is used for exactly the linearized resistivity sigma = 1/rho0*(1+alpha*DeltaT) that you mention, which is a predefined option ("Linearized resistivity") in the Current Conservation settings for the Electric Currents interface.

In the Copper node under Materials (and any other materials that you use), green check marks indicate the material properties that are used by the physics interfaces in the model. So, in an Electric Currents model, if you use "From material" to specify the electrical conductivity, the following material properties are used:

Electrical conductivity sigma
Relative permittivity epsilonr (for the constitutive relation)

If you instead use "Linearized resistivity" to specify the electrical conductivity, the following material properties are used:

Relative permittivity epsilonr
Reference resistivity rho0
Resistivity temperature coefficient alpha
Reference temperature Tref

Best regards,
Magnus Ringh, COMSOL
Hi, The reference resistivity rho0 is used for exactly the linearized resistivity sigma = 1/rho0*(1+alpha*DeltaT) that you mention, which is a predefined option ("Linearized resistivity") in the Current Conservation settings for the Electric Currents interface. In the Copper node under Materials (and any other materials that you use), green check marks indicate the material properties that are used by the physics interfaces in the model. So, in an Electric Currents model, if you use "From material" to specify the electrical conductivity, the following material properties are used: Electrical conductivity sigma Relative permittivity epsilonr (for the constitutive relation) If you instead use "Linearized resistivity" to specify the electrical conductivity, the following material properties are used: Relative permittivity epsilonr Reference resistivity rho0 Resistivity temperature coefficient alpha Reference temperature Tref Best regards, Magnus Ringh, COMSOL
Jürgen Gluch
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Posted: 1 decade ago 14.12.2011, 09:01 GMT-5
Thanks for the explanation. I find it sometimes really difficult to understand the implementation and where which input is used. Maybe a context related search function would help the user in such situations.

Jürgen
Thanks for the explanation. I find it sometimes really difficult to understand the implementation and where which input is used. Maybe a context related search function would help the user in such situations. Jürgen

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