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

  • Thread starter road2knowledge
  • Start date
  • Tags
    Unit
In summary, the unit of reluctance is At/Wb because it is analogous to resistance in electrical circuits. The underlined section in the equation can be promoted to the numerator, resulting in the simplified expression of At/Wb.
  • #1
road2knowledge
2
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
  • #2
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.
 
  • #3
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 cnh1995
  • #4
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 :(
 

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

1. What is the unit of Reluctance and why is it At/Wb?

The unit of Reluctance is At/Wb, where At stands for ampere-turns and Wb stands for webers. This unit is derived from the equation R = L/μA, where R is the Reluctance, L is the length of the magnetic circuit, μ is the permeability of the material, and A is the cross-sectional area. Since permeability is measured in webers per ampere-turn, the unit of reluctance becomes At/Wb.

2. How is Reluctance different from Resistance?

Reluctance is the measure of the opposition to the flow of magnetic flux in a material, while resistance is the measure of the opposition to the flow of electric current in a material. While resistance is affected by factors such as the material's temperature and composition, reluctance is mainly affected by the material's geometry and permeability.

3. Can you give an example of a material with high Reluctance?

Ferro-magnetic materials, such as iron and nickel, have high permeability and therefore high reluctance. This means that they resist the flow of magnetic flux more than other materials, making them ideal for use in magnetic circuits and transformers.

4. How is Reluctance related to the concept of magnetic flux?

Reluctance is directly proportional to the magnetic flux in a material. This means that as the reluctance increases, the magnetic flux decreases, and vice versa. This relationship is described by the equation Φ = B x A x μ x N, where Φ is the magnetic flux, B is the magnetic field strength, A is the cross-sectional area, μ is the permeability, and N is the number of turns in the coil.

5. Why is understanding Reluctance important in the study of magnetism?

Reluctance is a crucial concept in the study of magnetism because it helps us understand the behavior of magnetic materials and circuits. By understanding the factors that affect reluctance, we can design and optimize magnetic circuits for various applications, such as motors, generators, and transformers.

Back
Top