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PAGE 33 CONTINUED from Page
32
BASE UNIT - meter
(m) - LENGTH.
Up until 1983 the meter was defined as 1,650,763.73 wavelengths
in a vacuum of the orange-red line of the spectrum of krypton-86. And since
then it is determined to be the distance traveled by light in a vacuum in
1/299,792,45 of a second.
BASE UNIT - second
(s) - TIME
The second is defined as the duration of 9,192,631,770 cycles
of the radiation associated with a specified transition of the cesium-133
atom.
BASE UNIT - kilogram
(kg) - MASS
The standard for the kilogram is a cylinder of
platinum-iridium alloy kept by the International Bureau of Weights and
Measures in Paris.
A duplicate at the National Bureau of Standards serves as the mass
standard for the United States. The kilogram is the only base unit defined
by a physical object.
BASE UNIT - Kelvin
(K) and °Celsius (°C) - TEMPERATURE
The Kelvin is defined as the fraction 1/273.16 of the
thermodynamic temperature of the triple point of water; that is, the point
at which water forms an interface of solid, liquid and vapor. This is
defined as 0.01 °C on the Celsius scale and 32.02 °F on the Fahrenheit
scale. The temperature zero K (Kelvin) is called "absolute
zero". Basically, that’s where water freezes. (at sea
level)
BASE UNIT - ampere
(A) - ELECTRIC CURRENT
The ampere is defined as that current that, if maintained in
each of two long parallel wires separated by one meter in free space,
would produce a force between the two wires (due to their magnetic fields)
of 2 x 10-7 N (Newton) for each meter of length. (a Newton is
the unit of force that when applied to one kilogram mass would experience
an acceleration of one meter per second, per second).
BASE UNIT - candela
(cd) - LUMINOUS INTENSITY
The candela is defined as the luminous intensity of 1/600,000
of a square meter of a cavity at the temperature
of freezing
platinum (2,042 K).
BASE UNIT - mole
- (mol) AMOUNT OF SUBSTANCE
The mole is the amount of substance of a system that contains
as many elementary entities as there are atoms in 0.012 kilogram of
carbon-12.
BUT FOR MOST
EVERYDAY PURPOSES USE
BASE UNIT
meter length
Derived UNIT liter
volume
BASE UNIT kilogram
mass
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