Translate

THANKS

Thanks for being touch with us on Social media and online website

×
Thanks!
for visiting the electricaldon.com website.Received many applications for ITI ELECTRICIAN for job. Kindly note our team is working on it, shortly you will receive call from them.

APPLY only if you have Electrical wiremen or Electrical Supervisor Licenses its Mandatory. !

Thankyou for your Patients. !

Search This Blog

amazon 3

Pages

Tables of SI Units and Prefixes

 

Table I. Basic Units

defined by Conférence Générale des Poids et Mesures (CGPM) in the latest SI-brochure of 1998.

QuantityUnitSymbolDefinition
Length meter m 1983, 17th CGPM:  The path travelled by light in vacuum during a time interval of 1/299792458 seconds. This fixes the speed of light to exactly 299792458 m/s.
Mass kilogram kg 1901, 3rd CGPM:  Mass of the platinum-iridium prototype at BIPM in Sevres.
Time second s 1968, 13th CGPM:  One second equals 9192631770 periods of the radiation due to the transition between the two hyperfine levels of the ground state of Cesium 133.
Electric current ampere A 1948, 9th CGPM:  Given two parallel, rectilinear conductors of negligible circular cross-section positioned 1 m apart in vacuum, one ampere is the electric current which, passing through both of them, makes them attract each other by the force of 2.10-7 newtons per every meter of length. This fixes the permeability of vacuum to exactly 2π*10-7 H/m.
Temperature kelvin K 1968, 13th CGPM:  One degree K equals 1/273.16 of the thermodynamic temperature of the triple point of water.
Quantity of substance mole mol 1971, 14th CGPM:  The amount of a substance composed of as many specified elementary units (molecules, atoms) as there are atoms in 0.012 kg of Carbon 12.
Luminosity candle cd 1979, 16th CGPM:  The candle (or candela) is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540.1012 hertz and that has a radiant intensity in that direction of 1/683 W/sr.

Table II. Derived units with assigned names

defined by BIPM in the latest SI-brochure (1998) and its supplement (2000).

QuantityUnitSymbolEqualsDefinition / Note
Space and time:
Plane angle radian rad  The plane angle which,  when centered in a circle, cuts off an arc whose length is equal to the circle radius.
Solid angle steradian sr  The solid angle which,  when centered in a sphere, cuts off a cap whose surface equals that of a square having the radius as side.
Frequency hertz Hz 1 s-1[number of events or cycles]/[time]. 
Mechanics:
Force newton N 1 kg.m.s-2[mass].[acceleration]. 
Pressure pascal Pa 1 N.m-2[force]/[area]. Also: stress. 
Energy joule J 1 N.m [force].[length]. Also: Work, Heat 
Power watt W 1 J.s-1[energy]/[time]. Also: Radiant flux 
Thermodynamics:
Temperature celsius oC 1 K T [oC] = T [K] -273.15 (the offset is exact!). 
Electromagnetism:
Charge coulomb C 1 A.s [current].[time]. 
Potential volt V 1 W.A-1[power]/[current]. Only differences are measurable! 
Resistance ohm Ω 1 V.A-1[Δpotential]/[current]. 
Conductance siemens S 1 A.V-1[current]/[Δpotential]. 
Capacitance farad F 1 C.V-1[charge]/[Δpotential]. 
Inductance henry H 1 V.s.A-1[Δpotential]/[rate of change of current]. 
Magnetic flux weber Wb 1 J.A-1[energy]/[current]. 
Magnetic flux density tesla T 1 Wb.m-2[magnetic flux]/[area]. Also magnetic induction. 
Optics:
Luminous flux lumen lm 1 cd.sr [luminosity].[solid angle]. 
Illuminance lux lx 1 lm.m-2[luminous flux]/[area]. 
Convergence dioptry dioptry 1 m-1Inverse of focal length. 
Radioactivity and radiation:
Activity becquerel Bq 1 s-1[number of decay events]/[time]. 
Absorbed dose gray Gy 1 J.kg-1[energy]/[mass]. 
Dose equivalent sievert Sv 1 J.kg-1[energy]/[mass]. Absorbed dose re-normalized by biological effects. 
Chemistry:
Katalytic activity katal kat 1 mol.s-1[quantity of substance]/[time]. 

Table III a. SI Units prefixes

with examples of correct usage.

PrefixSymbolFactorExamples of usageOrigin
Yotta Y 10240.2 YW, 1.23Y [W] Greek 'octo' (eight, 10008)
Zetta Z 10213.33 Zs, 3.33Z [s] French 'sept' (seven, 10007)
Exa E 10181.23 Ekg, 1.23E [kg] Greek 'six' (10006)
Peta P 10157.5 Ps, 7.5P [s] Greek 'five' (10005)
Tera T 10120.5 Tm, 0.5T [m] Greek 'teras' = monster 
Giga G 1091.2 GΩ, 1.2G [Ω] Greek 'gigas' = giant 
Mega M 1067 MW, 7M [W] Greek 'megas' = large 
Kilo Kk 10333 km, 33K [m] Greek 'kilioi' = thousand 
hecto h 100 Deprecated by SI Greek 'hekaton' = hundred 
deca da 10 Deprecated by SI Greek 'deka' = ten 
deci d 0.1 Deprecated by SI Latin 'decima pars' = one tenth 
centi c 0.01 Deprecated by SI Latin 'centesima pars' = one hundredth 
milli mk 10-322 mm , 1.2m [m] Latin 'millesima pars' = one thousandth 
micro µu 10-62.7 uJ , 2.7µ [J] Greek 'mikros' = small 
nano n 10-92.2 nF, 2.2n [F] Latin 'nanus' = dwarf 
pico p 10-121.5 pA, 1.5p [A] Spanish 'pico' = minimal measure 
femto f 10-154.8 fs, 4.8f [s] Danish and Norvegian 'femten' = fifteen (10-15)
atto a 10-181.2 ag, 1.2a [g] Danish and Norvegian 'atten' = eighteen (10-18)
zepto z 10-210.2 zm, 1.2z [m] French 'sept' (seven, 1000-7)
yocto y 10-241 ys, 1y [s] Greek 'octo' (eight, 1000-8)

Table III b. Binary prefixes for Bytes

which are not a part of SI but which are in common use in informatics [see the note].

PrefixSymbolFactorValueExamples
Kilo KB 2101024 12345 KB = 12 641 280 bytes 
Mega MB 2201 048 576 420 MB fits in my PC's dynamic RAM 
Giga GB 2301 073 741 824 16 GB flash-memory pen drive costs $20 
Tera TB 2401 099 511 627 776 3.9 TB hard disks are a reality 
Peta PB 2501 125 899 906 842 624 13.5 PB is the CIA total memory capacity 
Exa EB 2601 152 921 504 606 846 976 1 EB is still a bit out of reach (AD 2010) 
Zetta ZB 2701 180 591 620 717 411 303 424 How many ZB to hard-copy a human being ??? 
Yotta YB 2801 208 925 819 614 629 174 706 176 1 YYB is still nothing compared with the Universe 

Table IV. Accepted non-SI units

compiled according to the US Federal Register (ref.4).

UnitofSymbolEqualsDefinition / Note
Degree of arc plane angle o(π/180) rad  
Minute of arc plane angle ' (1/60) o 
Second of arc plane angle " (1/60)'  
Minute time min 60 s  
Hour time h 60 min  
Day time d 24 h Notice that the duration of a day is not linked to Earth motion! 
Liter volume Ll 0.001 m3Often used sub-units are deciliter (dl) and centiliter.(cl). 
Gram mass g 0.001 kg A tolerated anomaly: the basic unit of mass (kg) has a prefix. 
Ton mass t 1000 kg More precise term: metric ton. 
Bit information bit - The smallest, dimensionless quantum of information 
Baud rate info flux Baud 1 bit.s-1[amount of information]/[time] 
Neper ratio Np log(A/B) Measure of a ratio A/B. The logarithms are in base 10. 
Bel ratio B 0.5 Np Mostly used as decibel (dB): 1 dB = (1/20) Np. 

Table V. Accepted non-SI units with experimental values.

For the most recent values of these constantly improving units, see Constants of Physics.

UnitofSymbolEqualsNote
Electronvolt energy eV 1.60217733(49).10-19 JEnergy to move an electron across a potential difference of 1 V. 
Astronomical unit length auAUua 1.49597870(30).10+11 mMean Earth-to-Sun distance. Also denoted as ua. 
Atomic mass unit mass u 1.6605402(10).10-27 kg1/12 of the rest mass of an unbound 12C atom in ground state. 

Table VI. Units deprecated by the SI

which are still in current use in most countries.

UnitofSymbolEqualsNote
Nautical mile length mile 1852 m  
Knot velocity knot 1 mile.h-1A nautical unit. 
Are area are 100 m2 
Hectar area ha 100 are 10000 m2 
Bar pressure bar 100000 Pa Almost 1 atm = 101325 Pa (an obsolete unit) 
Calory energy cal 4.1868 J Note: the conversion factor is fixed by convention. 
Ångström length Å 10-10 mUsed in atomic and molecular physics. 
Barn area b 10-28 m2Used in particle physics (collision cross-sections). 
Radioactivity and radiation:
Curie Radioactivity b 3.7*10+10 BqNote: the conversion factor is fixed by convention. 
Röntgen Radiation dose R 0.000258 Ci.kg-1Note: the conversion factor is fixed by convention. 
Rad Radiation dose rad 0.01 Gy  
Rem Equivalent dose rem 0.01 Sv  

No comments:

Post a Comment

Transformer