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Force Calculation in Magnetic fields module

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Hi While using this nice feature to calculate the force on body using the magnetic fields module I noticed the material description had no density specified. So I was wondering how and where does Comsol actually calculate the force. I mean if there's no density specified then mass is unknown and if I do F=ma then the result should either demand for m or assume it to be zero.

Thanks in advance to anyone who could help on this.

Harsh


6 Replies Last Post Jan 4, 2021, 4:35 a.m. EST
Edgar J. Kaiser Certified Consultant

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Posted: 4 years ago Jan 2, 2021, 11:57 a.m. EST

The magnetic force is not depending on the density or mass of the object. It would become relevant in case you wanted to calculate the movement of the object, i.e. when you couple the magnetic force with solid mechanics physics.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
The magnetic force is not depending on the density or mass of the object. It would become relevant in case you wanted to calculate the movement of the object, i.e. when you couple the magnetic force with solid mechanics physics. Cheers Edgar

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Posted: 4 years ago Jan 3, 2021, 5:20 a.m. EST

Thanks for the reply Edgar.

But then is this force not related to F=ma? If not then, could you please help me understand it a bit. I tried reading the module manual but I couldn't understand much. Is it the force on magnetic lines? Will the force on the body be different then?

Thanks for the reply Edgar. But then is this force not related to F=ma? If not then, could you please help me understand it a bit. I tried reading the module manual but I couldn't understand much. Is it the force on magnetic lines? Will the force on the body be different then?

Edgar J. Kaiser Certified Consultant

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Posted: 4 years ago Jan 3, 2021, 6:16 a.m. EST

It is a magnetic force. Nothing is being accelerated.

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
It is a magnetic force. Nothing is being accelerated.

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Posted: 4 years ago Jan 3, 2021, 6:40 a.m. EST

Thanks again Edgar. Just one last question please. Should I assume it to be force on magnetic field lines rather than bulk mass?

Thanks again Edgar. Just one last question please. Should I assume it to be force on magnetic field lines rather than bulk mass?

Edgar J. Kaiser Certified Consultant

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Posted: 4 years ago Jan 3, 2021, 4:08 p.m. EST

The magnetic force acts exactly on the entity you defined the force calculation on.

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
The magnetic force acts exactly on the entity you defined the force calculation on.

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Posted: 4 years ago Jan 4, 2021, 4:35 a.m. EST

I think it's still not too clear to me. I'll try reading the handbook again to try and understand this. By the way, thanks a lot for your efforts. Appreciate it.

I think it's still not too clear to me. I'll try reading the handbook again to try and understand this. By the way, thanks a lot for your efforts. Appreciate it.

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