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3.5 cm – width of film commonly used in motion pictures and still photography; 3.78 cm – amount of distance the Moon moves away from Earth each year [113] 4.3 cm – minimum diameter of a golf ball [114] 5 cm – usual diameter of a chicken egg; 5 cm – height of a hummingbird, the smallest-known bird; 5.08 cm – 2 inches,
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
d is the quantity of time in a day, G is the gravitational constant, M and m are the masses of the orbiting bodies, a is the length of the semi-major axis. To convert from radians per unit time to revolutions per day, consider the following:
In electromagnetism, Jefimenko's equations (named after Oleg D. Jefimenko) give the electric field and magnetic field due to a distribution of electric charges and electric current in space, that takes into account the propagation delay (retarded time) of the fields due to the finite speed of light and relativistic effects.
In calculation, the effects of r o are negligible, [1] so the equation is typically expressed as: λ = r m r i {\displaystyle \lambda ={\sqrt {\frac {r_{m}}{r_{i}}}}} The membrane resistance is a function of the number of open ion channels , and the axial resistance is generally a function of the diameter of the axon .
The term Friedmann equation sometimes is used only for the first equation. [3] a is the scale factor, G, Λ, and c are universal constants (G is the Newtonian constant of gravitation, Λ is the cosmological constant with dimension length −2, and c is the speed of light in vacuum).
The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum. It is a three-dimensional form of the wave equation. The homogeneous form of the equation, written in terms of either the electric field E or the magnetic field B, takes the form:
There are two London equations when expressed in terms of measurable fields: =, =. Here is the (superconducting) current density, E and B are respectively the electric and magnetic fields within the superconductor, is the charge of an electron or proton, is electron mass, and is a phenomenological constant loosely associated with a number density of superconducting carriers.