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<span class="os-number">D</span><span class="os-divider"> | </span><span class="os-text">Glossary of Key Symbols</span>

D | Glossary of Key Symbols

In this glossary, key symbols and notation are briefly defined.

Symbol Definition
any symbol ¯ any symbol ¯ size 12{ {overline {"any"`" symbol"}} } {} average (indicated by a bar over a symbol—e.g., v¯v¯ size 12{ {overline {v}} } {} is average velocity)
° C ° C size 12{°C} {} Celsius degree
° F ° F size 12{°F} {} Fahrenheit degree
// // size 12{"//"} {} parallel
⊥ ⊥ size 12{ ortho } {} perpendicular
∝ ∝ size 12{ prop } {} proportional to
± ± size 12{ +- {}} {} plus or minus
0 0 size 12{ {} rSub { size 8{0} } } {} zero as a subscript denotes an initial value
α α size 12{α} {} alpha rays
α α size 12{α} {} angular acceleration
α α size 12{α} {} temperature coefficient(s) of resistivity
β β size 12{β} {} beta rays
β β size 12{β} {} sound level
β β size 12{β} {} volume coefficient of expansion
β − β − size 12{β rSup { size 8{ - {}} } } {} electron emitted in nuclear beta decay
β + β + size 12{β rSup { size 8{+{}} } } {} positron decay
γ γ size 12{γ} {} gamma rays
γ γ size 12{γ} {} surface tension
γ = 1 / 1 − v 2 / c 2 γ = 1 / 1 − v 2 / c 2 size 12{γ= {1} slash { sqrt {1 - {v rSup { size 8{2} } } slash {c rSup { size 8{2} } } } } } {} a constant used in relativity
Δ Δ size 12{Δ} {} change in whatever quantity follows
δ δ size 12{δ} {} uncertainty in whatever quantity follows
ΔE ΔE size 12{ΔE} {} change in energy between the initial and final orbits of an electron in an atom
ΔE ΔE size 12{ΔE} {} uncertainty in energy
Δm Δm size 12{Δm} {} difference in mass between initial and final products
ΔN ΔN size 12{ΔN} {} number of decays that occur
Δp Δp size 12{Δp} {} change in momentum
Δp Δp size 12{Δp} {} uncertainty in momentum
Δ PE g Δ PE g size 12{Δ"PE" rSub { size 8{g} } } {} change in gravitational potential energy
Δθ Δθ size 12{Δθ} {} rotation angle
Δs Δs size 12{Δs} {} distance traveled along a circular path
Δt Δt size 12{Δt} {} uncertainty in time
Δt 0 Δt 0 size 12{Δt rSub { size 8{0} } } {} proper time as measured by an observer at rest relative to the process
ΔV ΔV size 12{ΔV} {} potential difference
Δx Δx size 12{Δx} {} uncertainty in position
ε 0 ε 0 size 12{ε rSub { size 8{0} } } {} permittivity of free space
η η size 12{η} {} viscosity
θ θ size 12{θ} {} angle between the force vector and the displacement vector
θ θ size 12{θ} {} angle between two lines
θ θ size 12{θ} {} contact angle
θ θ size 12{θ} {} direction of the resultant
θ b θ b size 12{θ rSub { size 8{b} } } {} Brewster's angle
θ c θ c size 12{θ rSub { size 8{c} } } {} critical angle
κ κ size 12{κ} {} dielectric constant
λ λ size 12{λ} {} decay constant of a nuclide
λ λ size 12{λ} {} wavelength
λ n λ n size 12{λ rSub { size 8{n} } } {} wavelength in a medium
μ 0 μ 0 size 12{μ rSub { size 8{0} } } {} permeability of free space
μ k μ k size 12{μ rSub { size 8{k} } } {} coefficient of kinetic friction
μ s μ s size 12{μ rSub { size 8{s} } } {} coefficient of static friction
v e v e size 12{v rSub { size 8{e} } } {} electron neutrino
π + π + size 12{π rSup { size 8{+{}} } } {} positive pion
π − π − size 12{π rSup { size 8{ - {}} } } {} negative pion
π 0 π 0 size 12{π rSup { size 8{0} } } {} neutral pion
ρ ρ size 12{ρ} {} density
ρ c ρ c size 12{ρ rSub { size 8{c} } } {} critical density, the density needed to just halt universal expansion
ρ fl ρ fl size 12{ρ rSub { size 8{"fl"} } } {} fluid density
ρ ¯ obj ρ ¯ obj size 12{ {overline {ρ}} rSub { size 8{"obj"} } } {} average density of an object
ρ / ρ w ρ / ρ w size 12{ {ρ} slash {ρ rSub { size 8{w} } } } {} specific gravity
τ τ size 12{τ} {} characteristic time constant for a resistance and inductance (RL)(RL) size 12{ \( ital "RL" \) } {} or resistance and capacitance (RC)(RC) size 12{ \( ital "RC" \) } {} circuit
τ τ size 12{τ} {} characteristic time for a resistor and capacitor (RC)(RC) size 12{ \( ital "RC" \) } {} circuit
τ τ size 12{τ} {} torque
Υ Υ size 12{Υ} {} upsilon meson
Φ Φ size 12{Φ} {} magnetic flux
ϕ ϕ size 12{ϕ} {} phase angle
Ω Ω size 12{ %OMEGA } {} ohm (unit)
ω ω size 12{ω} {} angular velocity
A A size 12{A} {} ampere (current unit)
A A size 12{A} {} area
A A size 12{A} {} cross-sectional area
A A size 12{A} {} total number of nucleons
a a size 12{a} {} acceleration
a B a B size 12{a rSub { size 8{B} } } {} Bohr radius
a c a c size 12{a rSub { size 8{c} } } {} centripetal acceleration
a t a t size 12{a rSub { size 8{t} } } {} tangential acceleration
AC AC size 12{"AC"} {} alternating current
AM AM size 12{"AM"} {} amplitude modulation
atm atm size 12{"atm"} {} atmosphere
B B size 12{B} {} baryon number
B B size 12{B} {} blue quark color
B ¯ B ¯ size 12{ {overline {B}} } {} antiblue (yellow) antiquark color
b b size 12{b} {} quark flavor bottom or beauty
B B size 12{B} {} bulk modulus
B B size 12{B} {} magnetic field strength
B int B int size 12{B rSub { size 8{"int"} } } {} electron’s intrinsic magnetic field
B orb B orb size 12{B rSub { size 8{"orb"} } } {} orbital magnetic field
BE BE size 12{"BE"} {} binding energy of a nucleus—it is the energy required to completely disassemble it into separate protons and neutrons
BE / A BE / A size 12{ {"BE"} slash {A} } {} binding energy per nucleon
Bq Bq size 12{"Bq"} {} becquerel—one decay per second
C C size 12{C} {} capacitance (amount of charge stored per volt)
C C size 12{C} {} coulomb (a fundamental SI unit of charge)
C p C p size 12{C rSub { size 8{p} } } {} total capacitance in parallel
C s C s size 12{C rSub { size 8{s} } } {} total capacitance in series
CG CG size 12{"CG"} {} center of gravity
CM CM size 12{"CM"} {} center of mass
c c size 12{c} {} quark flavor charm
c c size 12{c} {} specific heat
c c size 12{c} {} speed of light
Cal Cal size 12{"Cal"} {} kilocalorie
cal cal size 12{"cal"} {} calorie
COP hp COP hp size 12{ ital "COP" rSub { size 8{"hp"} } } {} heat pump’s coefficient of performance
COP ref COP ref size 12{ ital "COP" rSub { size 8{"ref"} } } {} coefficient of performance for refrigerators and air conditioners
cos θ cos θ size 12{"cos"θ} {} cosine
cot θ cot θ size 12{"cot"θ} {} cotangent
csc θ csc θ size 12{"csc"θ} {} cosecant
D D size 12{D} {} diffusion constant
d d size 12{d} {} displacement
d d size 12{d} {} quark flavor down
dB dB size 12{"dB"} {} decibel
d i d i size 12{d rSub { size 8{i} } } {} distance of an image from the center of a lens
d o d o size 12{d rSub { size 8{o} } } {} distance of an object from the center of a lens
DC DC size 12{"DC"} {} direct current
E E size 12{E} {} electric field strength
ε ε size 12{ε} {} emf (voltage) or Hall electromotive force
emf emf size 12{"emf"} {} electromotive force
E E size 12{E} {} energy of a single photon
E E size 12{E} {} nuclear reaction energy
E E size 12{E} {} relativistic total energy
E E size 12{E} {} total energy
E 0 E 0 size 12{E rSub { size 8{0} } } {} ground state energy for hydrogen
E 0 E 0 size 12{E rSub { size 8{0} } } {} rest energy
EC EC size 12{"EC"} {} electron capture
E cap E cap size 12{E rSub { size 8{"cap"} } } {} energy stored in a capacitor
Eff Eff size 12{ ital "Eff"} {} efficiency—the useful work output divided by the energy input
Eff C Eff C size 12{ ital "Eff" rSub { size 8{C} } } {} Carnot efficiency
E in E in size 12{E rSub { size 8{"in"} } } {} energy consumed (food digested in humans)
E ind E ind size 12{E rSub { size 8{"ind"} } } {} energy stored in an inductor
E out E out size 12{E rSub { size 8{"out"} } } {} energy output
e e size 12{e} {} emissivity of an object
e + e + size 12{e rSup { size 8{+{}} } } {} antielectron or positron
eV eV size 12{"eV"} {} electron volt
F F size 12{F} {} farad (unit of capacitance, a coulomb per volt)
F F size 12{F} {} focal point of a lens
F F size 12{F} {} force
F F size 12{F} {} magnitude of a force
F F size 12{F} {} restoring force
F B F B size 12{F rSub { size 8{B} } } {} buoyant force
F c F c size 12{F rSub { size 8{c} } } {} centripetal force
F i F i size 12{F rSub { size 8{i} } } {} force input
F net F net size 12{F rSub { size 8{"net"} } } {} net force
F o F o size 12{F rSub { size 8{o} } } {} force output
FM FM size 12{"FM"} {} frequency modulation
f f size 12{f} {} focal length
f f size 12{f} {} frequency
f 0 f 0 size 12{f rSub { size 8{0} } } {} resonant frequency of a resistance, inductance, and capacitance (RLC)(RLC) size 12{ \( ital "RLC" \) } {} series circuit
f 0 f 0 size 12{f rSub { size 8{0} } } {} threshold frequency for a particular material (photoelectric effect)
f 1 f 1 size 12{f rSub { size 8{1} } } {} fundamental
f 2 f 2 size 12{f rSub { size 8{2} } } {} first overtone
f 3 f 3 size 12{f rSub { size 8{3} } } {} second overtone
f B f B size 12{f rSub { size 8{B} } } {} beat frequency
f k f k size 12{f rSub { size 8{k} } } {} magnitude of kinetic friction
f s f s size 12{f rSub { size 8{s} } } {} magnitude of static friction
G G size 12{G} {} gravitational constant
G G size 12{G} {} green quark color
G ¯ G ¯ size 12{ {overline {G}} } {} antigreen (magenta) antiquark color
g g size 12{g} {} acceleration due to gravity
g g size 12{g} {} gluons (carrier particles for strong nuclear force)
h h size 12{h} {} change in vertical position
h h size 12{h} {} height above some reference point
h h size 12{h} {} maximum height of a projectile
h h size 12{h} {} Planck's constant
hf hf size 12{ ital "hf"} {} photon energy
h i h i size 12{h rSub { size 8{i} } } {} height of the image
h o h o size 12{h rSub { size 8{o} } } {} height of the object
I I size 12{I} {} electric current
I I size 12{I} {} intensity
I I size 12{I} {} intensity of a transmitted wave
I I size 12{I} {} moment of inertia (also called rotational inertia)
I 0 I 0 size 12{I rSub { size 8{0} } } {} intensity of a polarized wave before passing through a filter
I ave I ave size 12{I rSub { size 8{"ave"} } } {} average intensity for a continuous sinusoidal electromagnetic wave
I rms I rms size 12{I rSub { size 8{"rms"} } } {} average current
J J size 12{J} {} joule
J / Ψ J / Ψ size 12{ {J} slash {Ψ} } {} Joules/psi meson
K K size 12{K} {} kelvin
k k size 12{k} {} Boltzmann constant
k k size 12{k} {} force constant of a spring
K α K α size 12{K rSub { size 8{α} } } {} x rays created when an electron falls into an n=1n=1 size 12{n=1} {} shell vacancy from the n=3n=3 size 12{n=3} {} shell
K β K β size 12{K rSub { size 8{β} } } {} x rays created when an electron falls into an n=2n=2 size 12{n=2} {} shell vacancy from the n=3n=3 size 12{n=3} {} shell
kcal kcal size 12{"kcal"} {} kilocalorie
KE KE size 12{"KE"} {} translational kinetic energy
KE + PE KE + PE size 12{"KE"+" PE"} {} mechanical energy
KE e KE e size 12{"KE" rSub { size 8{e} } } {} kinetic energy of an ejected electron
KE rel KE rel size 12{"KE" rSub { size 8{"rel"} } } {} relativistic kinetic energy
KE rot KE rot size 12{"KE" rSub { size 8{"rot"} } } {} rotational kinetic energy
KE ¯ KE ¯ size 12{ {overline {"KE"}} } {} thermal energy
kg kg size 12{"kg"} {} kilogram (a fundamental SI unit of mass)
L L size 12{L} {} angular momentum
L L size 12{L} {} liter
L L size 12{L} {} magnitude of angular momentum
L L size 12{L} {} self-inductance
ℓ ℓ size 12{ℓ} {} angular momentum quantum number
L α L α size 12{L rSub { size 8{α} } } {} x rays created when an electron falls into an n=2n=2 size 12{n=2} {} shell from the n=3n=3 size 12{n=3} {} shell
L e L e size 12{L rSub { size 8{e} } } {} electron total family number
L μ L μ size 12{L rSub { size 8{μ} } } {} muon family total number
L τ L τ size 12{L rSub { size 8{τ} } } {} tau family total number
L f L f size 12{L rSub { size 8{f} } } {} heat of fusion
L f and L v L f and L v size 12{L rSub { size 8{f} } " and"` L rSub { size 8{v} } } {} latent heat coefficients
L orb L orb size 12{L rSub { size 8{"orb"} } } {} orbital angular momentum
L s L s size 12{L rSub { size 8{s} } } {} heat of sublimation
L v L v size 12{L rSub { size 8{v} } } {} heat of vaporization
L z L z size 12{L rSub { size 8{z} } } {} z - component of the angular momentum
M M size 12{M} {} angular magnification
M M size 12{M} {} mutual inductance
m m size 12{m} {} indicates metastable state
m m size 12{m} {} magnification
m m size 12{m} {} mass
m m size 12{m} {} mass of an object as measured by a person at rest relative to the object
m m size 12{m} {} meter (a fundamental SI unit of length)
m m size 12{m} {} order of interference
m m size 12{m} {} overall magnification (product of the individual magnifications)
m A X m A X size 12{m left ("" lSup { size 8{A} } X right )} {} atomic mass of a nuclide
MA MA size 12{"MA"} {} mechanical advantage
m e m e size 12{m rSub { size 8{e} } } {} magnification of the eyepiece
m e m e size 12{m rSub { size 8{e} } } {} mass of the electron
m ℓ m ℓ size 12{m rSub { size 8{ℓ} } } {} angular momentum projection quantum number
m n m n size 12{m rSub { size 8{n} } } {} mass of a neutron
m o m o size 12{m rSub { size 8{o} } } {} magnification of the objective lens
mol mol size 12{"mol"} {} mole
m p m p size 12{m rSub { size 8{p} } } {} mass of a proton
m s m s size 12{m rSub { size 8{s} } } {} spin projection quantum number
N N size 12{N} {} magnitude of the normal force
N N size 12{N} {} newton
N N size 12{N} {} normal force
N N size 12{N} {} number of neutrons
n n size 12{n} {} index of refraction
n n size 12{n} {} number of free charges per unit volume
N A N A size 12{N rSub { size 8{A} } } {} Avogadro's number
N r N r size 12{N rSub { size 8{r} } } {} Reynolds number
N ⋅ m N ⋅ m size 12{N cdot m} {} newton-meter (work-energy unit)
N ⋅ m N ⋅ m size 12{N cdot m} {} newtons times meters (SI unit of torque)
OE OE size 12{"OE"} {} other energy
P P size 12{P} {} power
P P size 12{P} {} power of a lens
P P size 12{P} {} pressure
p p size 12{p} {} momentum
p p size 12{p} {} momentum magnitude
p p size 12{p} {} relativistic momentum
p tot p tot size 12{p rSub { size 8{"tot"} } } {} total momentum
p tot ' p tot ' size 12{ { {p}} sup { ' } rSub { size 8{`"tot"} } } {} total momentum some time later
P abs P abs size 12{P rSub { size 8{"abs"} } } {} absolute pressure
P atm P atm size 12{P rSub { size 8{"atm"} } } {} atmospheric pressure
P atm P atm size 12{P rSub { size 8{"atm"} } } {} standard atmospheric pressure
PE PE size 12{"PE"} {} potential energy
PE el PE el size 12{"PE" rSub { size 8{"el"} } } {} elastic potential energy
PE elec PE elec size 12{"PE" rSub { size 8{"elec"} } } {} electric potential energy
PE s PE s size 12{"PE" rSub { size 8{s} } } {} potential energy of a spring
P g P g size 12{P rSub { size 8{g} } } {} gauge pressure
P in P in size 12{P rSub { size 8{"in"} } } {} power consumption or input
P out P out size 12{P rSub { size 8{"out"} } } {} useful power output going into useful work or a desired, form of energy
Q Q size 12{Q} {} latent heat
Q Q size 12{Q} {} net heat transferred into a system
Q Q size 12{Q} {} flow rate—volume per unit time flowing past a point
+ Q + Q size 12{+Q} {} positive charge
− Q − Q size 12{ - Q} {} negative charge
q q size 12{q} {} electron charge
q p q p size 12{q rSub { size 8{p} } } {} charge of a proton
q q size 12{q} {} test charge
QF QF size 12{"QF"} {} quality factor
R R size 12{R} {} activity, the rate of decay
R R size 12{R} {} radius of curvature of a spherical mirror
R R size 12{R} {} red quark color
R ¯ R ¯ size 12{ {overline {R}} } {} antired (cyan) quark color
R R size 12{R} {} resistance
R R size 12{R} {} resultant or total displacement
R R size 12{R} {} Rydberg constant
R R size 12{R} {} universal gas constant
r r size 12{r} {} distance from pivot point to the point where a force is applied
r r size 12{r} {} internal resistance
r ⊥ r ⊥ size 12{r rSub { size 8{ ortho } } } {} perpendicular lever arm
r r size 12{r} {} radius of a nucleus
r r size 12{r} {} radius of curvature
r r size 12{r} {} resistivity
r or rad r or rad size 12{"r or rad"} {} radiation dose unit
rem rem size 12{"rem"} {} roentgen equivalent man
rad rad size 12{"rad"} {} radian
RBE RBE size 12{"RBE"} {} relative biological effectiveness
RC RC size 12{ ital "RC"} {} resistor and capacitor circuit
rms rms size 12{"rms"} {} root mean square
r n r n size 12{r rSub { size 8{n} } } {} radius of the nth H-atom orbit
R p R p size 12{R rSub { size 8{p} } } {} total resistance of a parallel connection
R s R s size 12{R rSub { size 8{s} } } {} total resistance of a series connection
R s R s size 12{R rSub { size 8{s} } } {} Schwarzschild radius
S S size 12{S} {} entropy
S S size 12{S} {} intrinsic spin (intrinsic angular momentum)
S S size 12{S} {} magnitude of the intrinsic (internal) spin angular momentum
S S size 12{S} {} shear modulus
S S size 12{S} {} strangeness quantum number
s s size 12{s} {} quark flavor strange
s s size 12{s} {} second (fundamental SI unit of time)
s s size 12{s} {} spin quantum number
s s size 12{s} {} total displacement
sec θ sec θ size 12{"sec"θ} {} secant
sin θ sin θ size 12{"sin"θ} {} sine
s z s z size 12{s rSub { size 8{z} } } {} z-component of spin angular momentum
T T size 12{T} {} period—time to complete one oscillation
T T size 12{T} {} temperature
T c T c size 12{T rSub { size 8{c} } } {} critical temperature—temperature below which a material becomes a superconductor
T T size 12{T} {} tension
T T size 12{T} {} tesla (magnetic field strength B)
t t size 12{t} {} quark flavor top or truth
t t size 12{t} {} time
t 1 / 2 t 1 / 2 size 12{t rSub { size 8{ {1} slash {2} } } } {} half-life—the time in which half of the original nuclei decay
tan θ tan θ size 12{"tan"θ} {} tangent
U U size 12{U} {} internal energy
u u size 12{u} {} quark flavor up
u u size 12{u} {} unified atomic mass unit
u u size 12{u} {} velocity of an object relative to an observer
u ' u ' size 12{ { {u}} sup { ' }} {} velocity relative to another observer
V V size 12{V} {} electric potential
V V size 12{V} {} terminal voltage
V V size 12{V} {} volt (unit)
V V size 12{V} {} volume
v v size 12{v} {} relative velocity between two observers
v v size 12{v} {} speed of light in a material
v v size 12{v} {} velocity
v ¯ v ¯ size 12{ {overline {v}} } {} average fluid velocity
V B − V A V B − V A size 12{V rSub { size 8{B} } - V rSub { size 8{A} } } {} change in potential
v d v d size 12{v rSub { size 8{d} } } {} drift velocity
V p V p size 12{V rSub { size 8{p} } } {} transformer input voltage
V rms V rms size 12{V rSub { size 8{"rms"} } } {} rms voltage
V s V s size 12{V rSub { size 8{s} } } {} transformer output voltage
v tot v tot size 12{v rSub { size 8{"tot"} } } {} total velocity
v w v w size 12{v rSub { size 8{w} } } {} propagation speed of sound or other wave
v w v w size 12{v rSub { size 8{w} } } {} wave velocity
W W size 12{W} {} work
W W size 12{W} {} net work done by a system
W W size 12{W} {} watt
w w size 12{w} {} weight
w fl w fl size 12{w rSub { size 8{"fl"} } } {} weight of the fluid displaced by an object
W c W c size 12{W rSub { size 8{c} } } {} total work done by all conservative forces
W nc W nc size 12{W rSub { size 8{"nc"} } } {} total work done by all nonconservative forces
W out W out size 12{W rSub { size 8{"out"} } } {} useful work output
X X size 12{X} {} amplitude
X X size 12{X} {} symbol for an element
Z A X N Z A X N size 12{"" lSub { size 8{Z} } lSup { size 8{A} } X rSub { size 8{N} } } {} notation for a particular nuclide
x x size 12{x} {} deformation or displacement from equilibrium
x x size 12{x} {} displacement of a spring from its undeformed position
x x size 12{x} {} horizontal axis
X C X C size 12{X rSub { size 8{C} } } {} capacitive reactance
X L X L size 12{X rSub { size 8{L} } } {} inductive reactance
x rms x rms size 12{x rSub { size 8{"rms"} } } {} root mean square diffusion distance
y y size 12{y} {} vertical axis
Y Y size 12{Y} {} elastic modulus or Young's modulus
Z Z size 12{Z} {} atomic number (number of protons in a nucleus)
Z Z size 12{Z} {} impedance
Table D1