- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

The *magnetic reluctance (S)* is defined as the opposition offered by the magnetic circuit to the magnetic flux (Φ

The reluctance of a magnetic circuit depends upon its length (l), cross-sectional area (a) and permeability (μ) of the material. Thus, for a magnetic circuit (as shown in the figure),

The reluctance is directly proportional to the mean length of the magnetic circuit, i.e.

$$\mathrm{Magnetic\:reluctance,S\varpropto\:l\:\:\:\:....(1)}$$

The reluctance is inversely proportional to the cross-sectional area of the mag. circuit.

$$\mathrm{Magnetic\:reluctance,S\varpropto\:\frac{1}{a}\:\:\:\:....(2)}$$

The reluctance also depends upon the nature of material that makes up the mag. circuit.

eqs. (1) & (2), it can be written,

$$\mathrm{Magnetic\:reluctance,S\varpropto\:\frac{1}{a}}$$

$$\mathrm{Magnetic\:reluctance,S\varpropto\:\frac{1}{\mu_{0}\mu_{r}a}\:\:\:\:....(3)}$$

If mmf (NI) produced and magnetic flux (Φ) flowing in the magnetic circuit are the known quantities, then the reluctance of the magnetic circuit can be given as,

$$\mathrm{Reluctance,S=\frac{mmf(NI)}{Magnetic\:flux(\phi)}\:\:\:\:...(4)}$$

Since, the magnetic reluctance is given by

$$\mathrm{S=\frac{mmf(NI)}{Magnetic\:flux(\phi)}=\frac{Ampere\times\:Turn}{Weber}=AT/Wb}$$

Therefore, the magnetic reluctance is measured in AT/Wb.

**Note **– The reluctance of magnetic materials (like iron, steel etc.) is low due to their high relative permeability whereas the non-magnetic materials (such as air, wood, copper etc.) have high reluctance due to low relative permeability.

A magnetic circuit consists of an iron ring uniformly wounded with 1750 turns of insulated wire and a magnetising current of 1 A produces a magnetic flux of 1mWb. Neglect the effect of magnetic leakage. Determine the reluctance of magnetic circuit.

**Solution** −

**Reluctance****,**

$$\mathrm{S=\frac{Total\:mmf(NI)}{Magnetic\:flux()\phi}}$$

$$\mathrm{=\frac{1750\times\:1}{1\times\:10^{-3}}}$$

$$\mathrm{=1.75\times\:10^{6}\:\:\:AT/Wb}$$

The magnetic circuit is built up of iron of square cross section 2 cm sides and the mean length of the magnetic circuit is 54 cm. The relative permeability of material that makes up the magnetic circuit is 1200. Find the magnetic reluctance of the given magnetic circuit.

**Solution** −

**Area of cross-section,**

$$\mathrm{a=2\times\:2=4\:cm^{2}=4\times\:10^{-4}\:m^{2}}$$

**Reluctance,**

$$\mathrm{S=\frac{1}{\mu_{0}\mu_{r}a}=\frac{54\times\:10^{-2}}{(4\pi\times\:10^{-7})\times\:(1200)\times\:(4\times\:10^{-4})}}$$

$$\mathrm{\Rightarrow\:S=895700.64\:AT/Wb}$$

- Related Questions & Answers
- Mutual Inductance: Definition & Formula
- Know Sure Thing -Definition, Formula & Example
- What is Definition, Formula & Types of Bond Pricing?
- Kijun Line (Base Line) – Definition, Formula & Limitations
- Knowledge Economy – Definition, Examples & Issues
- What is Definition, Formula & Example of Key Rate Duration?
- Path Loss Definition, Overview and Formula
- Magnetism, Electromagnetism & Magnetic Materials
- Ammeter: Definition & Working Principle
- Parallel Circuit: Definition and Examples
- Bollinger Bands Formula & How to Use it?
- Give Explanation, Formula & Uses of K-Ratio
- Series-Parallel Circuit: Definition and Examples
- What is Module Testing? (Definition, Examples)
- Distribution Factor or Breadth Factor – Definition, Formula and Example

Advertisements