All The SI Units
All SI Units |
The System International (SI) is made up with 7 base units.
The 7 SI base units are….
Standard Units of measurement:
· m - Meter - Length
· s - Second - Time
· mol - Mole - Amount of Substance
· A - Ampere - Electric Current
· K - Kelvin - Temperature
· cd - Candela - Luminous Intensity
· kg - Kilogram – Mass
Quantity
|
Unit
|
Symbol
|
Definition
|
Length
|
Meter
|
m
|
The distance travelled by
light in vacuum in 1/299792458 second is called 1m.
|
Mass
|
kilogram
|
kg
|
1 kilogram is considered as
the definite amount of mass, which is the mass of a cylinder made of
platinum-iridium of height and diameter 3.9 cm kept in a certain building in
France.
|
Time
|
Second
|
s
|
The time required to
complete 9192631770 vibrations by a Cesium-133(Cs133) atom is
called one second.
|
Electric current
|
Ampere
|
A
|
When electric current flows
through two wires in the same direction they attract one another. The amount
of current that flows through two parallel wires separated by 1 m and if they
attract one another with 2107
N force per meter, that amount of current is called one ampere.
|
Temperature
|
Kelvin
|
K
|
The temperature we get when
the triple point temperature of water is divided by 273.16 is called one
Kelvin.
|
Amount of Substance
|
Mole
|
mol
|
One mole is defined as the
amount of substance that is contained in a definite number of fundamental
particles (molecule, atom or ion) which is equal to the number of atoms
contained in 0.012 kilogram of carbon-12 atom.
|
Luminous Intensity
|
Candela
|
cd
|
One candela is defined as
the amount of luminous intensity of a source of light which emitted in one steredian
solid angle of luminous intensity of 1/683 part of 1 watt.
|
These are the seven base system international units and their
identities. But in general, easily we can measure them by this way.
- The distance from the feet to the stomach of a person of normal height is nearly one meter.
- The water contained in one litter bottle or water of four glasses have a mass of nearly one kg.
- The time required to say three words ‘one thousand one’ is approximately one second.
- If three mobile phones are charging at the same time, one ampere electric current is used. (a mobile is charged at nearly 5 V. So, current consumption will be 5watt. If lights, fans, refrigerator of a residence run at 220 V and one ampere current is used then the power consumption will be 220 watt).
- If we feel the fever of anyone by touching with hand, then it will be said that his temperature has increased by one Kelvin.
- It is difficult to realize a mole, we can say a water filled large spoon contains one mole of water molecules. In one cup water, there are ten moles.
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