الأحد، 10 ديسمبر 2017

Units and Conversion Factors




SI Unit (Abbreviation)
Typical symbol
quantity
Mechanical
meter, m
x,y,z,l,d
Length
kilogram, kg
m
Mass
second, s
t
Time
meter/second, m/s
v, u
Velocity
newton, n
f
Force
newton-meter, nm
t
Torque
pascal, pa
p
Pressure
joule, j
w
Energy
watt, w
p,p
Power
radian, rad
α,β,γ,θ
Angle
radian/second, rad/s
ω
Angular velocity
Kg-m2
J
Mass polar moment of inertia
Electrical
coulomb, C
q, Q
Charge
ampere, A
i,I
(Electric) current
volt, V
v,V,e,E
Voltage
hertz, Hz
f
Frequency
radian per second, rad/s
ω
Radian frequency
voltampere, VA
S
Apparent power
watt, W
P
Average power
voltampere-reactive, var
Q
Reactive power
ohm, Ω
R
Resistance
henry, H
L
Inductance
farad, F
C
Capacitance
ohm, Ω
Z , X
Impedance, reactance
siemens, S
G
Conductance
siemens, S
Y, B
Admittance, susceptance
Thermal
kelvin, K
,θT
Temperature
watt, W
P, Q
Thermal power
joule, J
W
Heat energy
joule/kelvin, J/K
C
Thermal capacitance
watt/kelvin, W/K
G
Thermal capacitance
joule/(kelvin-kilogram), J/(K-kg)
cp
Specific heat
Magnetic
weber, Wb
φ
Flux
tesla, T
B
Flux density
ampere/meter, A/m
H
Magnetic field intensity
1/henry, H-1
Reluctance
henry, H
Permeance
ampere-turns, A

Magnetomotive force







SI Prefixes


10-24
y
yocto
1024
Y
yotta
10-21
z
zepto
1021
Z
zetta
10-18
a
atto
1018
E
exa
10-15
f
femto
1015
P
peta
10-12
p
pico
1012
T
tera
10-9
n
nano
109
G
giga
10-6
μ
micro
106
M
mega
10-3
m
milli
103
k
kilo
10-2
c
centi
102
h
hecto
10-1
d
deci
101
da
Deca  or deka
   Example usage: I= 118 A = 0.118 kA = 118000 mA.



Selected Constants
Permeability of free space = 0.4 π μH/m
Permittivity of free space = 8.8542 pf/m
Absolute zero (temperature) = 0 K = −273.2°C = −459.7°F = 0°R
Freezing point of water = 273.2 K = 0°C = 32°F = 491.7°R
g = acceleration of gravity = 9.807 m/s2 = 32.17 ft/s2
G = gravitational constant = 66.72 pN (m2) (kg-2)
c = speed of light in vacuum = 0.2998 m/ns = 299.8 km/s
Avogadro’s constant = 1.602 × 1023 = molecules per mole
e = charge on electron = 0.1602 aC
m0 = electron rest mass = 9.11 × 10-28 gram
1 revolution = 2π radians = 360 degrees
1 standard atmosphere (atm) = 760 mm Hg = 101.3 kPa = 29.92 in Hg =
14.696 psi
Air density = 1.225 kg/m3@ 1 atmosphere, 15°C, 1 u = 1 amu = 1 atomic
mass unit = 1.661 × 10-27 kg
1 toe (1 tonne oil equivalent) = 41.868 GJ = 1270 m3 natural gas (STP) = 2.3 tonnes coal   
1 ton TNT = 4.184 GJ


Selected Conversion Factors
1 inch = 2.54 cm; 1 foot = 12 inches; 1 meter = 3.28084 feet
1 pound force (lbf)= 4.4482 newtons; 1 kilogram = 2.188 pound mass (lbm)
J in kg-m2 = 0.0.04246 × J in lbm-ft2
1 atomic mass unit = u = 1.661 × 10-27 kg
Electron/positron mass = 0.000549 u
Proton mass = 1.007276 u
Neutron mass = 1.008665 u
1 slug = 14.59 kilogram
1 foot-pound = 1.356 newton-meter
1 horsepower = 746 watts
1 British Thermal Unit (BTU) = 1055 joule
1 calorie = 4.19 joule
Temperature in Kelvin (K) = TK
Temperature in degrees Celsius (°C) = TC = TK – 273.2
Temperature in degrees Fahrenheit (°F) = TF = 1.8TC + 32
Temperature in degrees Rankine (°R) = TR = TF + 459.7
1 milligauss = 1 mG = 0.1 microtesla = 0.1 μT
1 ton (refrigeration) = 3517 watts = 12 kBTU/hr
1 tonne = 1 metric ton = 1000 kg
Speed in rad/s = (2π/60) × speed in rpm (rpm = revolutions per minute)
1 day = 24 hours; 1 hour = 60 minutes; 1 minute = 60 seconds
1 nautical mile = 6000 ft = 1.1364 mile
1 knot = 1 nautical mile per hour = 1.1364 mph = 0.5080 m/s

Temperature Scales


Kelvin
Centigrade
Rankine
Fahrenheit
373 K
100°C
672°R
212°F
311 K
38°C
560°R
212°F
273 K
0°C
492°R
32°F
255 K
−18°C
460°R
0°F
0 K
−273°C
0°R
−460°F


Notes
One unit C = one unit K; one unit F = one unit R; one unit K = I.8 F units.
Absolute zero (0 K) = −459.67°F  = −273.15°C.
Normal human body temperature is 98.2°F (36.8°C).

Related posts:
Electrical unit

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