Can't understand why the unit of Reluctance is At/Wb

  • Thread starter Thread starter road2knowledge
  • Start date Start date
  • Tags Tags
    Unit
Click For Summary
SUMMARY

The unit of Reluctance is defined as At/Wb, which is derived from the relationship between magnetic flux (Wb) and magnetomotive force (At). The confusion arises from the cancellation of units during the derivation process. Specifically, when manipulating the equation for reluctance, the term m² cancels out, leading to the simplified unit of At/Wb. This is analogous to electrical resistance, where reluctance corresponds to resistance in circuits.

PREREQUISITES
  • Understanding of basic electromagnetic concepts, including magnetic flux and magnetomotive force.
  • Familiarity with unit analysis and dimensional analysis in physics.
  • Knowledge of algebraic manipulation of equations.
  • Basic understanding of analogies between electrical and magnetic systems.
NEXT STEPS
  • Review the principles of magnetic circuits and their similarities to electrical circuits.
  • Study the concept of magnetic reluctance in detail, including its applications.
  • Learn about the relationship between magnetic field strength and magnetic flux density.
  • Explore advanced topics in electromagnetism, such as Maxwell's equations.
USEFUL FOR

Students studying physics, particularly those focusing on electromagnetism, as well as educators looking to clarify concepts related to magnetic circuits and reluctance.

road2knowledge
Messages
2
Reaction score
0

Homework Statement


I can't figure out why the unit of Reluctance is At/Wb and not (At/Wb)m2
This is what I have from my textbook, with the red oval area being the part that I'm totally confused about
Untitled.png

Homework Equations

The Attempt at a Solution


So the m/m cancels out to 1 making it
R=1/(Wb/At·m2)
which is = (At·m2)/Wb
then I have no idea what happened so that m2 vanished and R became At/Wb

Please help me clear up my confusion
I can't sleep scratching my head T_T
Thanks a bunch!
 
Physics news on Phys.org
road2knowledge said:
I can't figure out why the unit of Reluctance is At/Wb and not (At/Wb)m2
As your book says, reluctance is analogous to resistance in electrical circuits. Similarly, flux is analogous to current and mmf (Ampere turns) is analogous to voltage.
 
Note the division operator:
upload_2016-5-6_8-5-30.png

The underlined bit is in the denominator of the denominator, so to speak. Hence it can be "promoted" to the numerator of the overall expression.

upload_2016-5-6_8-11-58.png
 
  • Like
Likes   Reactions: cnh1995
gneill said:
Note the division operator:
View attachment 100341
The underlined bit is in the denominator of the denominator, so to speak. Hence it can be "promoted" to the numerator of the overall expression.

View attachment 100342
OHHHHHHH!
Thank you so much!
I think I'll need to go back to secondary algebra for a bit of revision :(
 

Similar threads

  • · Replies 13 ·
Replies
13
Views
2K
Replies
7
Views
2K
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
Replies
28
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
7K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K