circumference

(noun)

The line that bounds a circle or other two-dimensional figure

Examples of circumference in the following topics:

  • Eratosthenes' Experiment

    • Using basic geometry, Greek mathematician Eratosthenes determined the circumference of the Earth within 0.4% error of today's value.
    • Eratosthanes sought to know the circumference of Earth.
    • To measure its circumference, he devised a method that used the rays of sunlight that hit Earth which he assumed arrive parallel.
    • But the circumference of a sphere equals π times its diameter:
    • Thus his measurement of the Earth circumference (some 2000 years ago) was in error: Less than actual by only one-tenth of a percent.

  • Angular Position, Theta

    • We know that for one complete revolution, the arc length is the circumference of a circle of radius r.
    • The circumference of a circle is 2πr.
    • The arc length Δs is described on the circumference.

  • Wave Nature of Matter Causes Quantization

    • Assuming that an integral multiple of the electron's wavelength equals the circumference of the orbit, we have:
    • The third and fourth allowed circular orbits have three and four wavelengths, respectively, in their circumferences.

  • de Broglie and the Bohr Model

    • By assuming that the electron is described by a wave and a whole number of wavelengths must fit along the circumference of the electron's orbit, we have the equation:
    • (c) If the wavelength does not fit into the circumference, the electron interferes destructively; it cannot exist in such an orbit.

  • Using Interference to Read CDs and DVDs

    • This is because the center tracks are smaller in circumference and therefore can be read quicker.

  • Kinematics of UCM

    • The arc length $\Delta s$ is described on the circumference.

  • Solenoids, Current Loops, and Electromagnets

    • Electromagnets are employed for many uses: from a wrecking yard crane that lifts scrapped cars, to controlling the beam of a 90-km-circumference particle accelerator, to the magnets in medical imaging machines (for other examples see ).

  • Simple Harmonic Motion and Uniform Circular Motion

    • You can prove this yourself by remembering that the circumference of a circle is 2*pi*r, so if the object traveled around the whole circle (one circumference) it will have gone through an angle of 2pi radians and traveled a distance of 2pi*r.

  • Rotational Angle and Angular Velocity

    • The arc length $\Delta s$ is described on the circumference.

  • Dynamics of UCM

    • Now the average speed $v$ is the circumference divided by the period: