Theory:

Concentric circles:
Two or more circles of the same radii constructed from the same fixed point are called concentric circles.
Circular ring:
The area between two concentric circles is the circular ring.
Circular Ring.PNG
 
The width of the circular ring can be obtained by the difference between the radii or diameters of two concentric circles.
 
\(\text{Width of the circular ring}\) \(=\) \(\text{Outer radii}\) \(-\) \(\text{Inner radii}\)
 
or
 
\(\text{Width of the circular ring}\) \(=\) \(\frac{\text{Outer diameter} {-} \text{Inner diameter}}{2}\)
  
  
Construction of concentric circles:
 
Now, let us look at the construction of concentric circles step-by-step.
 
Draw two concentric circles with \(3cm\) and \(7cm\) as radii.
 
Step \(1\): Draw a rough diagram with the given specifications.
 
Rough diagram.PNG
 
Step \(2\): Mark the fixed point as '\(O\)'.
 
Step \(3\): Draw a line segment of \(3cm\) from '\(O\)'. Mark the other end of the line segment as '\(A\)'.
 
Step \(4\): With '\(O\)' as centre, rotate the compass firmly from '\(A\)' until the inner circle is achieved.
 
Step \(5\): Draw a line segment of \(7cm\) from '\(O\)'. Mark the other end of the line segment as '\(B\)'.
 
Step \(6\): With '\(O\)' as centre, rotate the compass firmly from '\(B\)' until the outer circle is achieved.
 
Step \(7\): To find the width of the circular ring.
 
\(\text{Width of the circular ring}\) \(=\) \(\text{Outer radius}\) \(-\) \(\text{Inner radius}\)
 
\(=\) \(7\) \(-\) \(3\)
 
\(=\) \(4\) \(cm\)
 
  
The practical construction is as follows:
 
Construction of concentric circles.gif