About the International System of
Units (SI) Part III. SI Table
Gordon J. Aubrecht II, Ohio State University, Columbus and Marion, OH
Anthony P. French, Massachusetts Institute of Technology, Cambridge, MA
Mario Iona,a University of Denver, Denver, CO
This is the third part in a series of notes that will help teachers understand what SI is and how to use
it in a common-sense way. This part contains several essential SI tables.
B
Table I. Base units.
efore discussing more details of SI, we will summarize
the essentials in a few tables that can serve as ready
references. If a unit isn’t listed in Tables I-IV, it is not
part of SI or specifically allowed for use with SI. The units
and symbols that are sufficient for most everyday applications
are given in bold.
m kg
s K A mol
cd meter, metre
kilogram
second kelvin ampere mole
candela length
mass
time
temperature
electric current
amount of substance
luminous intensity
Table II. Derived SI units with special names, listed alphabetically by name.
Derived quantity
Name
Symbol
activity (of a radionuclide)
becquerel
Bq
electric charge, quantity of electricity
coulomb
C
degree Celsius
°C
Celsius temperature
In terms of
other SI units
In terms of SI
base units
s-1
A.s
K
A2 . s4/(m2 .
kg)
capacitance
farad
F
C/V
absorbed dose, specific energy (imparted), kerma
gray
Gy
J/kg
m2/s2
inductance
henry
H
Wb/A
kg . m2/(s2 . A2)
frequency
hertz
Hz
energy, work, quantity of heat
joule
J
catalytic activity
katal
kat
luminous flux
lumen
lm
cd. sr
lux
lx
lm/m2
newton
N
ohm
W
V/A
pressure, stress
pascal
Pa
N/m2
kg . m2/(s3 . A2)
kg/(m . s2)
plane angle
radian
rad
m/m = 1
siemens
S
A/V
s3 . A2/(kg . m2)
sievert
Sv
J/kg
m2/s2
steradian
sr
m2/m2 = 1
kg/(s2 . A)
illuminance
force
electric resistance
electric conductance
dose equivalent, ambient dose equivalent, directional dose
equivalent, personal dose equivalent, equivalent dose
solid angle
s-1
N.m
kg . m2/s2
mol · s–1
cd . sr
cd . sr/m2
kg . m/s­2
magnetic flux density
tesla
T
Wb/m2
electric potential, potential difference, electromotive force
volt
V
W/A
power,* radiant flux
watt
W
J/s
kg . m2/(s3 . A)
kg . m2/s3
magnetic flux
weber
Wb
Vs
kg . m2/(s2 . A)
* In the specialized field of electric power, the var is the generally used unit name and symbol for “reactive power” (this is power that is not consumed
but flows back and forth in a circuit, i.e, the imaginary part of the complex power). Both the IEC and IEEE have adopted the term at electrical engineers’ behest, despite physicists’ continued insistence that power is power and thus measured in watts. The var stands for “volt ampere reactive” and
its equivalent value in SI units is 1 var = 1 V·A.
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The Physics Teacher ◆ Vol. 50, January 2012
DOI: 10.1119/1.3670073
Table III. Prefixes in SI.
yotta-
zetta-
exa-
peta-
tera-
giga-
mega-
kilo-
hecto-
deka-
deci-
centi-
milli-
micro-
nano-
pico-
femto-
atto-
zepto-
yocto-
Y
Z
E
P
T
G
M
k
h
dk
d
c
m
m
n
p
f
a
z
y
1,000,000,000,000,000,000,000,000
1,000,000,000,000,000,000,000
1,000,000,000,000,000,000
1,000,000,000,000,000
1,000,000,000,000
1,000,000,000
1,000,000
1,000
100
10
1
1/10
1/100
1/1000
1/1,000,000
1/1,000,000,000 1/1,000,000,000,000
1/1,000,000,000,000,000
1/1,000,000,000,000,000,000
1/1,000,000,000,000,000,000,000
1/1,000,000,000,000,000,000,000,000
(gig-a)
(nann-o)
(peek-o)
Table IV. Non-SI units used with SI.
time
minute
time
hour
h
1 h = 60 min = 3600 s
time
day
d
1 d = 24 h = 86,400 s
plane angle
degree*
°
1° = (π/180) rad
plane angle
minute
'
1' = (1/60)° = (π/10,800) rad
"
1" = (1/60)' = (π/648,000) rad
plane angle
second
liter
tonne, metric ton
min
1, L
t
min = 60 s
1 L = 1 dm3 = 10-3 m3
1 t = 103 kg
(a)
electronvolt
eV
1.602 177 333 10 3 10-19 J
(a, b)
unified atomic mass unit
u
1.660 540 23 3 10-27 kg
(a)
astronomical unit
AU
1.495 979 31011 m
The use of these units destroys coherence.
(a) These units do not have a defined value, but their SI equivalent has been determined experimentally.
(b) In biochemistry, the dalton (Da) is also accepted.
* The degree symbol is attached to the number. The degree may be used with decimal subdivision.
Gordon J. Aubrecht II, Department of Physics,
Ohio State University, Columbus, OH 43210-1117
and Marion, OH 43302-5695; aubrecht@mps.ohio-state.edu
Anthony P. French, Department of Physics,
Massachusetts Institute of Technology, Cambridge,
MA 02139-4307; apfrench@mit.edu
(a) deceased
The Physics Teacher ◆ Vol. 50, January 2012
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