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RosanelladC1-Visitor
1-Visitor
April 15, 2013
Solved

Scalar fields: partial derivatives, grad f and |grad f|

  • April 15, 2013
  • 4 replies
  • 2487 views

Hello All

I'm setting up a worksheet to enable me to check my workings for when I need to solve a two or three dimensional scalar field by hand (cylindrical & spherical polar coordinates).


Mathcad partially differentiate some but not all and it flags some variable. Also, I cannot get grad f or |grad f|.

I'm obviously setting up something incorrectly.

Could someone point me in the right direction, please?

I'm enclosing my worksheet.

Best answer by RosanelladC

Thank you Alan for the corrected worksheet

Question: I've noticed that MathC does not return a scalar for | grad f | . Should it not return a scalar value instead of a vectorial value, as I'm not working out | grad f | in the direction of its unit vector grad f / | grad f | ?

4 replies

AlanStevens19-Tanzanite
19-Tanzanite
April 16, 2013

The attached shows some modifications to the cylindrical section. It might (or might not!) be of some help.

Alan

RosanelladC1-VisitorAuthorAnswer
1-Visitor
April 16, 2013

Thank you Alan for the corrected worksheet

Question: I've noticed that MathC does not return a scalar for | grad f | . Should it not return a scalar value instead of a vectorial value, as I'm not working out | grad f | in the direction of its unit vector grad f / | grad f | ?

AlanStevens19-Tanzanite
19-Tanzanite
April 17, 2013

Rosanella di-Costanzo wrote:

Thank you Alan for the corrected worksheet

Question: I've noticed that MathC does not return a scalar for | grad f | . Should it not return a scalar value instead of a vectorial value, as I'm not working out | grad f | in the direction of its unit vector grad f / | grad f | ?

It does return a scalar value. However, to see this more clearly it's probably best to define ep as a function and then insert specific values when it is called. For example:

Grad.PNG

(Actually, ep need only be defined as a function of x and y. I've included z above, but it's superfluous).

Alan

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