Carts and Wheels - Introduction to Circles

A circle is a perfectly round flat shape with no corners or sides. Visually, it is a closed curve where every point on the boundary is at an equal distance from a fixed point in the middle called the center.

The Center is the fixed point in the exact middle of the circle. When drawing a circle with a compass, the metal pin stays at the center while the pencil moves around it to form the shape.

The Radius ($r$) is the distance from the center of the circle to any point on its boundary. You can visualize it as a single spoke of a bicycle wheel connecting the middle hub to the outer rim.

The Diameter ($d$) is a straight line that passes through the center and connects two points on the circle's edge. It is the longest possible line you can draw inside a circle and is exactly double the length of the radius.

A Chord is a straight line segment whose endpoints both lie on the circle. While the diameter is the most famous chord (passing through the center), other chords can be shorter and do not have to cross the center.

The Circumference is the total length of the boundary of the circle. If you were to cut a circular ring and straighten it out into a line, the length of that line would be the circumference.

Drawing circles can be done using round objects like bangles, bottle caps, or coins for fixed sizes. For specific measurements, a Compass is used where the distance between the needle and the pencil is adjusted to match the desired radius.