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The tau (τ), also called the tau lepton, tau particle, tauon or tau electron, is an elementary particle similar to the electron, with negative electric charge and a spin of 1 2 . Like the electron, the muon, and the three neutrinos, the tau is a lepton, and like all elementary particles with half-integer spin, the tau has a ...
Tau in astronomy is a measure of optical depth, or how much sunlight cannot penetrate the atmosphere. In the physical sciences, tau is sometimes used as time variable, to avoid confusing t as temperature. Time constant (also relaxation time) of any system, such as an RC circuit. Torque, the rotational force in mechanics.
Time constant. In physics and engineering, the time constant, usually denoted by the Greek letter τ (tau), is the parameter characterizing the response to a step input of a first-order, linear time-invariant (LTI) system. [1][note 1] The time constant is the main characteristic unit of a first-order LTI system. It gives speed of the response.
Geometry index. In coordination chemistry and crystallography, the geometry index or structural parameter (τ) is a number ranging from 0 to 1 that indicates what the geometry of the coordination center is. The first such parameter for 5-coordinate compounds was developed in 1984. [1] Later, parameters for 4-coordinate compounds were developed. [2]
Half-life (symbol t½) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely ...
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured.
m = mass of each molecule (all molecules are identical in kinetic theory), γ (p) = Lorentz factor as function of momentum (see below) Ratio of thermal to rest mass-energy of each molecule: θ = k B T / m c 2 {\displaystyle \theta =k_ {\text {B}}T/mc^ {2}} K2 is the modified Bessel function of the second kind.
The RC time constant, denoted τ (lowercase tau), the time constant (in seconds) of a resistor–capacitor circuit (RC circuit), is equal to the product of the circuit resistance (in ohms) and the circuit capacitance (in farads): It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to ...