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How to get the first time derivative of defined variables?

Posted 2012/02/07 1:54 GMT-5 2 Replies

Mingjie Jia
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I defined "rho_E" as charge density, its unit is C/m^3. when I coupled the Electric Current, the Current source(A/m^3) Qj was required. I think Qj equals the first time derivative of rho_E, but I don't know how to express it.
2 Replies Last Post 2012/02/07 3:01 GMT-5
Wiktor Stenström
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Posted: 1 decade ago 2012/02/07 2:53 GMT-5
If you want to create a variable that is the first time derivative you can use the "d"-operator. In your case you can define:
Qj = d(rho_E,t)
This operator is described further under "The differentation operators" in the help documentation.
If you want to create a variable that is the first time derivative you can use the "d"-operator. In your case you can define: Qj = d(rho_E,t) This operator is described further under "The differentation operators" in the help documentation.
Mingjie Jia
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Posted: 1 decade ago 2012/02/07 3:01 GMT-5

If you want to create a variable that is the first time derivative you can use the "d"-operator. In your case you can define:
Qj = d(rho_E,t)
This operator is described further under "The differentation operators" in the help documentation.


Thanks a lot!
[QUOTE] If you want to create a variable that is the first time derivative you can use the "d"-operator. In your case you can define: Qj = d(rho_E,t) This operator is described further under "The differentation operators" in the help documentation. [/QUOTE] Thanks a lot!

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