Exploring the Annulus: Definition, Properties, and Applications

Comprehensive Definition, Description, Examples & Rules 

Edulyte Maths Lessons

Learn Maths anytime, anywhere

Sign Up
What will you learn

Introduction to the Annulus

In mathematics, an annulus is a shape that forms in between two circles with a common center. It is shaped like a ring. It is referred to as the area of two concentric circles. This page of Edulyte’s is more informative for you because it will cover the concepts related to the annulus, its role in mathematics, and so on. You will develop an understanding of the concepts, and the section of the worksheet at the end is surprisingly the best part of this page. You can test your knowledge and understanding of the annulus by practising on a worksheet.

Definition of an annulus in geometry

An annulus is a shape formed between two concentric circles. Annulus is like a round ring with two dimensions. Annulus has breadth with inner and outer surface areas. It is not a circle itself, but it is formed from two circle spaces.

Explanation of its unique properties and characteristics

An annulus is a specific point in a larger circle. It should not be at the boundary of the inner circle. It is referred to as the point distance from any other point in a circle. Annulus has symbols of ‘r’ and R. Here, both ‘r’ denotes the radius. ‘r’ is the radius of a small circle, and ‘R’ is the radius of a large circle.

You can find out the area of the annulus by subtracting the area of the inner and outer circles.

  • The area of the annulus is calculated as π(R²-r²).  
  • The diameter of the annulus is  2π(R+r). It is calculated by adding the radius of both circles. 
  • Breadth is R – r, which means when you subtract the outer radius from the inner radius of the circle, you will get the breadth.

Importance of the annulus in various mathematical and real-world contexts 

It is crucial to understand the importance of this topic from every perspective. 

  • This concept is relevant from a geometrical perspective. It is important to find out the perimeter and area of a circle. 
  • The concept of the annulus is important for science because it is useful for atoms, electrons, and many other concepts. 
  • Annulus is important for geography to calculate the earth’s radius. 
  • There are various other fields in which this concept is useful; therefore, you must have a general understanding of the concept.

Understanding Annular Shapes

Annular shapes are not similar to a circle or a ring. There is a slight difference between them. Below, you will find the difference between a circle and an annular one.

Differentiating between the annulus and other geometric shapes (e.g., circle, ring)

  • Circle 

The circle doesn’t have any holes, and it is at an equal distance from its fixed point. The circle shape has two dimensions and a circumference. 

  • Ring 

Annulus sometimes refers to a ring, but there is a difference between both of them. A ring doesn’t contain two circles. It is just like a round-shaped object. 

  • Annulus 

whereas an annulus has two dimensions. It lies between the spaces of two concentric circles, and it has a point at the outer circle boundary.

Geometrical construction of an annulus

There are several steps that you need to follow when constructing an annulus. 

  • You need to draw two circles with the same center. These two circles would be an outer and an inner circle. 
  • After drawing your circle, you need to mention the radius (r, R) of both the outer and inner circles. 
  • You need to join the points of both the inner and outer circles to form an annulus. 
  • Lines should not intersect each other, and it must look like a ring shape.

Visual representation of annular shapes.

A visual representation of the annulus helps you understand the concept with clarity. You can better understand the annulus and its construction through visuals.

Annulus Meaning and Significance

Annulus is a ring-shaped circle that has its importance in the field of mathematics. This concept is not new, but it has a history.

Historical context and origin of the term “annulus.”

Annulus is an ancient concept. The word itself is derived from the Latin ‘annulus’. Annulus came into use after geometry. It has relevance with geometry.

The cultural and scientific significance of the annulus in different fields

  • It is significant in geometry. Archimedes found the importance of the annulus for understanding the concepts related to a circle, like its perimeter and area.
  • An annulus is useful for measuring the circular area. If an engine wants a circular design, then they are supposed to know the concept of an annulus.
  • It is important to understand the geographical concepts. The study of Earth, planets, their rotation, and position can be calculated with the annulus. 
  • It has cultural significance as well because it is referred to as a ring, and it is also celebrated as a ceremony. 

Throughout history, this concept has evolved, and at the present time it has become significant for all the existing fields. 

Annulus Definition and Formulas

An annulus is a shape that forms between two concentric circles. You will better understand the concept in further sections.

Formal mathematical definition of the annulus

Annulus is significant for geometry. The radius of two circles lies in the distance from the fixed center of the inner and outer circles.

Deriving the formula for the area and perimeter of an annulus

  • Annulus Area 

The area of the annulus is useful in calculating the area of the outer circle and inner circle. You need to simply subtract the outer radius from the inner radius to get the annulus area.

  • πR²- πr² = π(R²-r²)  
  • Annulus perimeter

Perimeter includes the addition of two circumstances: inner and outer circles.

  • 2πr+2πR. = 2π( R+ r) 

Numerical examples illustrating the application of the formulas 

Find out the area of the annulus if the radius of the outer circle is 5 and the inner circle’s radius is 2. 

  • Area of annulus = π(52-22) , 22/7 (value of pie) 

Area = 22/7 * 21 

Area =66 

Find the perimeter of the annulus with the radius of the outer and inner circles being 8 and 6.

  • The perimeter of the annulus

 2π(8+6)  

 2π *14 

2*22/7*14 

The perimeter is 88.

Properties of Annular Regions

Annular regions have properties related to area, perimeter, and so on.

Identifying and explaining the properties of an annulus

  • The breadth of an annulus is calculated by subtracting the inner radius of a circle from the outer circle.
    • B= R-r 
  • The area of the annulus is π(R²-r²).
  • The perimeter of the annulus is 2π( R+ r).
  • Annulus’ outer inner circle has the same center point.

Relationship between the radius and diameter of an annulus

The diameter is the full measurement of the circle’s width, whereas the radius is half of it. Both are interlinked.

  • The diameter is the 2R  of the outer circle.
  • The diameter of the inner circle is 2R.

Interconnection between the annulus and its components (e.g., inner and outer circles)

  • The inner and outer circles have the same fixed point.
  • Both circles have different radiuses that further consider the annulus breadth.
  • Areas and perimeter are calculated by considering the radius of both the inner and outer circles. 

Area Comparison: Annulus vs. Circle 

An annulus is not similar to a circle. A circle has an equal distance from its fixed point, and it doesn’t contain any other circle. On the other hand, an annulus has a ring-like shape and is a concentric circle with an outer and inner circle.

Contrasting the area of an annulus with that of a complete circle

  • The area of a circle is the measurement of a single circle area that is R2. 
  • On the other hand, the area of the annulus is the measurement of the area of the outer and inner circles, which is π( R² – r²).

Practical examples highlight scenarios where annular shapes are prevalent. 

  • Disc and vehicle are the shapes that represent the shape of the annulus.
  • The pipes that are used in the house also have the same shape as the annulus.
  • The shapes of the planets and earth present the annulus shape.
  • There are various other things that exist that give us visuals of an annular shape.

Step Up Your Math Game Today!

Free sign-up for a personalised dashboard, learning tools, and unlimited possibilities!

learn maths with edulyte

Key Takeaways

  1. Annulus is the easiest concept of mathematics that is related to concentric circles.

  2. It is not similar to a circle or ring. 

  3. Annulus consists of inner and outer circles with different radii. 

  4. It is having different formulas for calculating area and perimeter.

  5. It is a concept related to daily life.

  6. You must check your understanding of annulus through the worksheet.

  7. You can improve your understanding of annulus through daily practice.

Quiz

Check your score in the end

Quiz

Check your score in the end
Question of

Question comes here

Frequently Asked Questions

The circumference of the annulus is 2π( R+ r).

Annulus and Circle do not have similarities. An annulus is a shape formed between the spaces of two concentric circles. In comparison,  a circle has two dimensions shapes with a fixed centre.

Concentric annuli are shapes that form between two concentric circles. It consists of the radius of the outer circle and the inner circle.

You can see the application of annuli in the present world. It is useful for calculating the area of a circle. To measure the planet, and so on.

A circular motion reflects the formation of an annulus shape.

Annular shapes are available everywhere. You can find the presence of annularity in the form of shells in nature and arches in architecture.

Like
Share it with your friends

Learn Maths

Newsletters

Sign up for Learner Newsletter

Subscribe now for discounts, learning resources, blogs and guides. We do not spam.

We won’t pass your details on to anyone else. By clicking the subscribe button you agree to our Terms of Use and Privacy Policy.

Newsletters

Sign up for Tutor Newsletter

Subscribe now for discounts, learning resources, blogs and guides. We do not spam.

We won’t pass your details on to anyone else. By clicking the subscribe button you agree to our Terms of Use and Privacy Policy.

PTE Tutorials: Customised Packages for Every Learner

Standard

$75 AUD

One time

popular

Premium

$275 AUD

One time

Elite

$575 AUD

One time