Decibel

a unit for measuring the level of sound which has the symbol dB.

Taken from Dictionary of Science

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The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity) relative to a specified or implied reference level. Since it expresses a ratio of two quantities with the same unit, it is a dimensionless unit. A decibel is one tenth of a bel, a seldom-used unit.

The decibel is widely known as a measure of sound pressure level, but is also used for a wide variety of other measurements in science and engineering (particularly acoustics, electronics, and control theory) and other disciplines. It confers a number of advantages, such as the ability to conveniently represent very large or small numbers, a logarithmic scaling that roughly corresponds to the human perception of sound and light, and the ability to carry out multiplication of ratios by simple addition and subtraction.

The decibel symbol is often qualified with a suffix, which indicates which reference quantity or frequency weighting function has been used. For example, "dBm" indicates that the reference quantity is one milliwatt, while "dBu" is referenced to 0.775 volts RMS.

The definitions of the decibel and bel use base-10 logarithms. For a similar unit using natural logarithms to base e, see neper.

Taken from Wikipedia

Farad

the unit in which CAPACITANCE is measured. It is usually denoted by the symbol F. For example, the capacitance (C) of a conductor measured in farads is the charge (in coulombs) needed to raise the potential by one volt i.e. 1 farad = 1 coulomb per volt (1F = 1 CV^-1). As the farad itself is usually too large a quantity for most applications, the practical unit is the microfarad (µF), or one millionth of a farad.

Taken from Dictionary of Science

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The farad (symbol: F) is the SI unit of capacitance. The term farad is named after the English physicist Michael Faraday.

A farad is the charge in coulombs a capacitor will accept for the potential across it to change 1 volt. A coulomb is 1 ampere second. Example: A 47 mA current causes the voltage across a capacitor to increase 1 volt per second. It therefore has a capacitance of 47 mF. It has the base SI representation of s⁴·A²·m^-2·kg^-1. Further equalities follow:

The most commonly used multiples and submultiples in electrical and electronic usage are the microfarad, nanofarad and picofarad.

Taken from Wikipedia

Calcium

a metallic substance with the symbol Ca which is common in nature being found in both plants and animals. It is essential for the normal growth and development of animals, being found in bones, teeth, blood and nerves.

Taken from Dictionary of Science

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Calcium (pronounced /ˈkælsiəm/, KAL-see-əm) is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.

Calcium is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca²⁺ into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bones and shells, calcium is the most abundant metal by mass in many animals.

Taken from Wikipedia