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This means that the time constant is the time elapsed after 63% of V max has been reached Setting for t = for the fall sets V(t) equal to 0.37V max, meaning that the time constant is the time elapsed after it has fallen to 37% of V max. The larger a time constant is, the slower the rise or fall of the potential of a neuron.
It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage.
The relaxation time is a measure of the time it takes for one object in the system (the "test star") to be significantly perturbed by other objects in the system (the "field stars"). It is most commonly defined as the time for the test star's velocity to change by of order itself. [6] Suppose that the test star has velocity v.
The time constant τ is the e −1 -life, the time until only 1/e remains, about 36.8%, rather than the 50% in the half-life of a radionuclide. Thus, τ is longer than t 1/2. The following equation can be shown to be valid:
The reason for this is that the choice of a system of units may arbitrarily select any physical constant as its basis, making the question of which constant is undergoing change an artefact of the choice of units. [5] [6] [7] For example, in SI units, the speed of light has been given a defined value in 1983. Thus, it was meaningful to ...
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It is characterized by the spin–lattice relaxation time, a time constant known as T 1. There is a different parameter, T 2 , the spin–spin relaxation time , which concerns the exponential relaxation of the transverse component of the nuclear magnetization vector ( perpendicular to the external magnetic field).
For example, the evolution of the outer rings of Saturn is significantly influenced by radiation pressure. As a consequence of light pressure, Einstein [21] in 1909 predicted the existence of "radiation friction", which would oppose the movement of matter. He wrote: "radiation will exert pressure on both sides of the plate.