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It was originally defined as "the quantity or mass of radium emanation in equilibrium with one gram of radium (element)", [1] but is currently defined as 1 Ci = 3.7 × 10 10 decays per second [4] after more accurate measurements of the activity of 226 Ra (which has a specific activity of 3.66 × 10 10 Bq/g [5]).
The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. [ 1] It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue, air, water, or any other substance.
Dram (unit) The dram (alternative British spelling drachm; apothecary symbol ʒ or ℨ; [ a] abbreviated dr) [ 4][ 5]: C-6–C-7 [ 6] is a unit of mass in the avoirdupois system, and both a unit of mass and a unit of volume in the apothecaries' system. [ 5] It was originally both a coin and a weight in ancient Greece. [ 7]
The amount of energy required to warm one gram of air-free water from 19.5 to 20.5 °C at standard atmospheric pressure. [b] Mean calorie: cal mean: ≈ 4.190 J ≈ 0.003 971 BTU ≈ 1.164 × 10 −6 kW⋅h ≈ 2.615 × 10 19 eV Defined as 1 ⁄ 100 of the amount of energy required to warm one gram of air-free water from 0 to 100 °C at ...
Approximate definition of a mole based on 12 grams of carbon-12. The Avogadro constant was historically derived from the old definition of the mole as the amount of substance in 12 grams of carbon-12 (12 C); or, equivalently, the number of daltons in a gram, where the dalton is defined as 1/12 of the mass of a 12 C atom. [9]
Each contains about 14 grams or 17.7 ml of ethanol. A standard drink or (in the UK) unit of alcohol is a measure of alcohol consumption representing a fixed amount of pure alcohol. The notion is used in relation to recommendations about alcohol consumption and its relative risks to health. It helps to educate alcohol users. [ 1]
1 Bq = 1 s −1. A special name was introduced for the reciprocal second (s −1) to represent radioactivity to avoid potentially dangerous mistakes with prefixes.For example, 1 μs −1 would mean 10 6 disintegrations per second: (10 −6 s) −1 = 10 6 s −1, [4] whereas 1 μBq would mean 1 disintegration per 1 million seconds.
An equivalent definition of the dyne is "that force which, acting for one second, will produce a change of velocity of one centimetre per second in a mass of one gram". [ 3 ] One dyne is equal to 10 micronewtons, 10 −5 N or to 10 nsn (nano sthenes ) in the old metre–tonne–second system of units .