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v. t. e. The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour).
Atmospheric electricity describes the electrical charges in the Earth's atmosphere (or that of another planet ). The movement of charge between the Earth's surface, the atmosphere, and the ionosphere is known as the global atmospheric electrical circuit. Atmospheric electricity is an interdisciplinary topic with a long history, involving ...
Femtosecond. A femtosecond is a unit of time in the International System of Units (SI) equal to 10 −15 or ⁄1 000 000 000 000 000 of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. [1] For context, a femtosecond is to a second as a second is to about 31.71 million years; a ray of light travels ...
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 ), i.e.: It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of ...
Capillary refill test on index finger pulp. [2] Capillary refill time ( CRT) is defined as the time taken for color to return to an external capillary bed after pressure is applied to cause blanching. [3] It can be measured by holding a hand higher than heart-level and pressing the soft pad of a finger or fingernail until it turns white, then ...
Method of image charges. The method of image charges (also known as the method of images and method of mirror charges) is a basic problem-solving tool in electrostatics. The name originates from the replacement of certain elements in the original layout with imaginary charges, which replicates the boundary conditions of the problem (see ...
The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 mi ). Just as the second forms the basis for other units of time, the light-second can ...
The elementary charge e, i.e. the negative charge on a single electron or the positive charge on a single proton: 10 −18: atto-(aC) ~ 1.8755 × 10 −18 C: Planck charge: 10 −17: 1.473 × 10 −17 C (92 e) – Positive charge on a uranium nucleus (derived: 92 x 1.602 × 10 −19 C) 10 −16: 1.344 × 10 −16 C: Charge on a dust particle in ...