Concentric circles :
In this section, we are going to learn about Concentric circles.
Already we are familiar with Circles.
When a small stone was dropped in still water, you might have seen circular ripples were formed. Which is the center of these circles ?
Is it not the place where the stone was dropped ?
The circles with different measures of radii and with the same center are called concentric-circles. The center is known as common center.
Circles drawn in a plane with a common center and different radii are called concentric-circles. See the figure given below.
Look at the following two figures :
The above figure represents two concentric-circles.
In the above figure, the area between the two concentric -circles are shaded with red color.
The red colored area is known as circular ring.
In the figure given above, C₁ and C₂ are two circles having the same center O with different radii r₁ and r₂ respectively.
Circles C₁ and C₂ are called concentric-circles.
The area bounded between the two circles is known as circular ring.
Width of the circular ring = OB – OA = r₂ - r₁ ( r₂ > r₁)
Draw concentric-circles with radii 3 cm and 5 cm and shade the circular ring.
Find its width.
Given: The radii are 3 cm and 5 cm.
Steps for construction :
Step 1 :
Draw a rough diagram and mark the given measurements.
Step 2 :
Take any point O and mark it as the center.
Step 3 :
With O as center and draw a circle of radius OA = 3 cm
Step 4 :
With O as center and draw a circle of radius OB = 5 cm.
Thus the concentric-circles C₁ and C₂ are drawn.
Width of the circular ring = OB – OA
Width of the circular ring = 5 – 3
Width of the circular ring = 2 cm.
After having gone through the stuff given above, we hope that the students would have understood "Concentric-circles".
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