Learning Objectives
- Learn about circles and their properties
- Understand the concept of radius and diameter
- Draw circles using a compass or round objects
- Recognize circles in wheels and everyday objects
Key Concepts
What is a Circle?
A circle is a perfectly round shape. Every point on a circle is the same distance from the centre. Wheels, coins, bangles, and the face of a clock are all circles. Circles are special because they roll smoothly. That is why wheels are always round!
Centre, Radius, and Diameter
The centre is the middle point of a circle. The radius is the distance from the centre to any point on the circle. The diameter is the distance from one side of the circle to the other, passing through the centre. The diameter is always double the radius. If the radius is 5 cm, the diameter is 10 cm.
Drawing Circles
You can draw a circle using a compass. Fix the needle at one point (the centre), open the compass to the size you want (the radius), and turn it around to draw the circle. You can also draw circles by tracing around round objects like a coin, bangle, or bottle cap.
Wheels in Our Life
Wheels are one of the most important inventions. Cars, buses, bicycles, and trains all have wheels. A cart has 2 wheels, a bicycle has 2 wheels, a car has 4 wheels, and a truck may have 6 or more wheels. Without wheels, it would be very hard to move things from one place to another.
Important Terms
- Circle: A perfectly round shape where all points are the same distance from the centre
- Centre: The middle point of a circle
- Radius: The distance from the centre to the edge of the circle
- Diameter: The distance across the circle through the centre (= 2 x radius)
- Compass: A tool used to draw circles of a specific size
Quick Revision
- A circle is perfectly round with no corners
- All points on a circle are at the same distance from the centre
- Diameter = 2 x Radius
- Radius = Diameter ÷ 2
- Use a compass to draw exact circles
- Wheels are circles and are used in many vehicles