** Eccentricity vs Concentricity
**

Eccentricity and concentricity are two mathematical concepts related to the geometry of conic section. The two parameters are related to each other and describe the conic section shape. The concepts are adopted in many science and engineering fields.

**More about Eccentricity (e)**

Eccentricity is a measure of the deviation of a conic section from the perfect circle. In fact, the conic sections are categorized using the eccentricity as a parameter. A circle has no eccentricity (e=0), ellipse has an eccentricity between zero and one ( 0<e<1). A parabola has an eccentricity of one (e=1), and a hyperbola has an eccentricity greater than one (e>1).

The linear eccentricity of a conic section (c) is the distance between the center of the conic section and either one of its foci. Then the eccentricity of a conic section can be defined as the ratio between the linear eccentricity and the length of the semi-major axis (a), e=c/a.

Few among the numerous uses of eccentricity as a measure are machine design, orbital mechanics, and fiber optics manufacturing.

In engineering, one of the major concern when designing or manufacturing a circular or a cylindrical component is how perfect the shape of the circles is. This is measured by the eccentricity of the cross section. In orbital mechanics, eccentricity gives the degree of elongation of the orbit.

**More about Concentricity**

Concentric means two or more shapes sharing the same center, generally a system of circles. The concept has significant practical application because, in manufacturing and engineering, it gives a measure of consistency of the designed system.

For example, consider a roller of a press (printing machine), which is a cylindrical shaft consisting of many layers of materials. If each layer is not aligned such that the center of each layer coincides across the same axis, the roller will not function properly. The same idea applies to gear systems, fiber optic cables and piping systems.

When considering two circles, concentricity can be formulated as the ratio between the minimum difference between the radii to the maximum difference: i.e. C=D_{min}/D_{max} .

**What is the difference between Eccentricity and Concentricity?**

• Eccentricity is the measure of elongation of a conic section.

• Concentricity is the measure of alignment of two or more shapes on the same axis.

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