(Study Material) CBSE Physics Study Material (SI Derived units)

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CBSE Physics Study Material

SI Derived units

Examples of SI derived units whose names and symbols include SI derived units with special names and symbols 

Derived quantity				Name				Symbol
dynamic viscosity				pascal second			Pa·s
moment of force				newton meter			N·m
surface tension				newton per meter			N/m
angular velocity				radian per second			rad/s
angular acceleration			radian per second squared		rad/s2
heat flux density, irradiance			watt per square meter		W/m2
heat capacity, entropy			joule per kelvin			J/K
specific heat capacity, specific entropy	joule per kilogram kelvin		J/(kg·K)
specific energy				joule per kilogram			J/kg
thermal conductivity			watt per meter kelvin		W/(m·K)
energy density				joule per cubic meter		J/m3
electric field strength			volt per meter			V/m
electric charge density			coulomb per cubic meter		C/m3
electric flux density			coulomb per square meter		C/m2
permittivity				farad per meter			F/m
permeability				henry per meter			H/m
molar energy				joule per mole			J/mol
molar entropy, molar heat capacity		joule per mole kelvin		J/(mol·K)
exposure (x and rays)			coulomb per kilogram		C/kg
absorbed dose rate			gray per second			Gy/s
radiant intensity				watt per steradian			W/sr
radiance					watt per square meter steradian	W/(m2·sr)
catalytic (activity) concentration	katal per cubic meter		kat/m3

Examples of SI derived units whose names and symbols include SI derived units with special names and symbols 

Units outside the SI that are accepted for use with the SI 
Name				Symbol			Value in SI units
minute (time)			min			1 min = 60 s 
hour				h			1 h = 60 min = 3600 s 
day				d			1 d = 24 h = 86 400 s 
degree (angle)			°			1° = ( π/180) rad
minute (angle)			´			1´ = (1/60)° = (π/10 800) rad 
second (angle)			"			1" = (1/60)´ = (π/648 000) rad 
liter				L			1 L = 1 dm3 = 10-3 m3 
metric ton (a)			t			1 t = 103 kg 
neper				Np			1 Np = 1
bel (b)				B			1B = (1/2) ln 10 Np (c)
electronvolt (d)			eV			1 eV = 1.602 18 x 10-19 J, approximately 
unified atomic mass unit (e)		u			1 u = 1.660 54 x 10-27 kg, approximately 
astronomical unit (f)		ua			1 ua = 1.495 98 x 1011 m, approximately

(a) In many countries, this unit is called "tonne.''
(b) The bel is most commonly used with the SI prefix deci: 1 dB = 0.1 B.

(c) Although the neper is coherent with SI units and is accepted by the CIPM, it has not been adopted by the General Conference on Weights and Measures (CGPM, Conférence Générale des Poids et Mesures) and is thus not an SI unit.

(d) The electronvolt is the kinetic energy acquired by an electron passing through a potential difference of 1 V in vacuum. The value must be obtained by experiment, and is therefore not known exactly.

(e) The unified atomic mass unit is equal to 1/12 of the mass of an unbound atom of the nuclide 12C, at rest and in its ground state. The value must be obtained by experiment, and is therefore not known exactly.

(f) The astronomical unit is a unit of length. Its value is such that, when used to describe the motion of bodies in the solar system, the heliocentric gravitation constant is (0.017 202 098 95)2 ua3·d-2. The value must be obtained by experiment, and is therefore not known exactly.

The liter in Table given in the previous page deserves comment. This unit and its symbol l were adopted by the CIPM in 1879. The alternative symbol for the liter, L, was adopted by the CGPM in 1979 in order to avoid the risk of confusion between the letter l and the number 1. Thus, although both l and L are internationally accepted symbols for the liter, to avoid this risk the preferred symbol for use in the United States is L. Neither a lowercase script letter l nor an uppercase script letter L are approved symbols for the liter.

Other units outside the SI that are currently accepted for use with the SI by NIST are given in Table 7. These units, which are subject to future review, should be defined in relation to the SI in every document in which they are used; their continued use is not encouraged. The CIPM currently accepts the use of all of the units given in Table 7 with the SI except for the curie, roentgen, rad, and rem. Because of the continued wide use of these units in the United States, NIST still accepts their use with the SI. 

Other units outside the SI that are currently accepted for use with the SI, subject to further review 
Name			Symbol			Value in SI units
nautical mile					1 nautical mile = 1852 m
knot						1 nautical mile per hour = (1852/3600) m/s
are			a			1 a = 1 dam2 = 102 m2
hectare			ha			1 ha = 1 hm2 = 104 m2 
bar			bar			1 bar = 0.1 MPa = 100 kPa = 1000 hPa = 105 Pa
ångström			Å			1 Å = 0.1 nm = 10-10 m
barn			b			1 b = 100 fm2 = 10-28 m2
curie			Ci			1 Ci = 3.7 x 1010 Bq
roentgen			R			1 R = 2.58 x 10-4 C/kg
rad			rad			1 rad = 1 cGy = 10-2 Gy
rem			rem			1 rem = 1 cSv = 10-2 Sv

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