Catalogue of 118 elements
1. q · Electric charge
C. Amount of charge; q = ∫I dt. Energy also depends on voltage.
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2. ρ · Volume charge density
C/m³. Charge per unit volume, used in field calculations.
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3. σq · Surface charge density
C/m². Charge per unit surface area of a conductor or dielectric.
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4. λq · Linear charge density
C/m. Charge per unit length, useful for a long-conductor model.
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5. I · Electric current
A. Rate of charge flow. Heating and load limits depend on current.
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6. J · Current density
A/m². Current per cross-sectional area; helps assess local heating.
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7. E · Electric field strength
V/m. Force per unit charge, used in insulation design.
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8. B · Magnetic flux density
T. Describes the magnetic field in motors and transformers.
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9. D · Electric displacement
C/m². Combines the electric field and material polarization.
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10. H · Magnetic field strength
A/m. In a linear medium B = μH. Used to design magnetic circuits.
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11. φ · Electric potential
V. Potential energy per unit charge relative to a chosen reference.
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12. ℰ · Electromotive force
V. Source work per unit charge; characterizes a generator or battery.
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13. Ppol · Polarization
C/m². Electric dipole moment per unit volume of material.
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14. Mmag · Magnetization
A/m. Magnetic moment per unit volume, important for magnetic cores.
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15. ε · Permittivity
F/m. Material response to an electric field; affects capacitance.
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16. μ · Permeability
H/m. Relates flux density and magnetic field strength in a material model.
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17. σ · Conductivity
S/m. Ability to conduct current; in a simple model J = σE.
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18. ρe · Resistivity
Ω·m. Inverse of material conductivity; depends on temperature.
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19. χe · Electric susceptibility
1. Dimensionless polarization response to an electric field.
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20. χm · Magnetic susceptibility
1. Dimensionless magnetization response to a magnetic field.
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21. tanδ · Dielectric loss tangent
1. Characterizes dielectric losses; supports insulation diagnostics.
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22. Ebd · Dielectric strength
V/m. Field at which breakdown can occur under specified test conditions.
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23. μc · Carrier mobility
m²/(V·s). Relates carrier drift velocity to electric field strength.
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24. n · Carrier concentration
m⁻³. Number of free charge carriers per unit volume.
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25. ΨD · Electric displacement flux
C. Flux of D through a surface, related to free charge.
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26. Φ · Magnetic flux
Wb. Surface integral of magnetic flux density.
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27. λ · Flux linkage
Wb. Sum of fluxes linked by turns; determines induced voltage.
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28. U · Voltage
V. Potential difference; an essential supply characteristic at the delivery point.
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29. R · Resistance
Ω. At current I, resistive power losses equal I²R.
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30. G · Conductance
S. Reciprocal resistance of a resistive element: G = 1/R.
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31. C · Capacitance
F. Ability to store charge. Ideal capacitor energy equals CU²/2.
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32. L · Inductance
H. Relates current and flux linkage. A linear inductor stores LI²/2.
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33. M · Mutual inductance
H. Magnetic coupling between circuits, central to transformer operation.
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34. Z · Impedance
Ω. Complex opposition to alternating current, with resistive and reactive parts.
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35. Y · Admittance
S. Reciprocal impedance: Y = 1/Z.
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36. X · Reactance
Ω. Imaginary part of impedance, set by capacitance and inductance.
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37. Bs · Susceptance
S. Imaginary part of admittance, used in compensation calculations.
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38. τ · Time constant
s. Characteristic transient time; affects response speed.
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39. f₀ · Resonant frequency
Hz. Resonance frequency; relevant to filters and operating stability.
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40. Qf · Quality factor
1. Describes losses and resonance sharpness in an oscillating system.
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41. We · Electrical energy
J; kWh. Energy transferred over an interval: W = ∫P dt; 1 kWh = 3.6 MJ.
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42. Wm · Magnetic energy
J. Energy stored in a magnetic field, for example in an inductor.
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43. Wem · Electromagnetic energy
J. Energy of electric and magnetic fields in the region considered.
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44. u · Energy density
J/m³. Energy per unit volume; useful for fields and storage.
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45. p(t) · Instantaneous power
W. In a single-phase circuit p(t) = u(t)i(t); energy requires integration.
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46. P · Active power
W; kW. Average rate of energy transfer over a specified interval.
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47. Q · Reactive power
var; kvar. Describes energy exchange with fields in alternating-current operation.
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48. S · Apparent power
VA; kVA. For one phase S = Urms·Irms; relevant to equipment loading.
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49. S̲ · Complex power
VA. For sinusoidal operation S̲ = P + jQ; its magnitude is apparent power.
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50. PF · Power factor
1. Ratio P/S. Includes waveform effects under the adopted definition of S.
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51. cosφ · Displacement factor
1. Cosine of the phase angle between fundamental voltage and current.
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52. Sp · Poynting vector
W/m². Electromagnetic energy flux density; Sp = E × H.
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53. pv · Volume power density
W/m³. Local energy conversion rate; the resistive contribution equals J·E.
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54. Wloss · Energy losses
J; kWh. Energy lost within a chosen boundary; reduction requires a comparable balance.
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55. η · Efficiency
1; %. Useful output energy divided by input energy for a specified boundary.
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56. f · Frequency
Hz. Cycles per second; a system condition and frequency-control parameter.
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57. ω · Angular frequency
rad/s. Rate of phase change; ω = 2πf.
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58. T · Oscillation period
s. Duration of one cycle: T = 1/f. Service duration is specified separately.
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59. θ · Phase
rad. Position within a cycle relative to a chosen reference.
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60. Δφ · Phase difference
rad. Relative phase of two signals; important for power and synchronization.
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61. X̂ · Amplitude
[X]. Maximum signal excursion from the chosen mean level.
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62. Xpp · Peak-to-peak value
[X]. Difference between the maximum and minimum signal values.
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63. Xrms · Root mean square
[X]. Square root of the mean squared signal; used for current and voltage.
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64. X̄ · Mean value
[X]. Average over a stated window. Window length affects peak assessment.
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65. Xabs · Mean rectified value
[X]. Mean of the absolute signal value.
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66. CF · Crest factor
1. Peak magnitude divided by RMS; indicates sharp peaks.
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67. FF · Form factor
1. RMS divided by mean rectified value.
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68. dX/dt · Rate of change
[X]/s. For power, describes the rate of load increase or reduction.
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69. Xh · Harmonic amplitude
[X]. Magnitude of a selected harmonic, used in power-quality analysis.
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70. SX(f) · Spectral density
[X]²/Hz. Distribution of mean-square signal value over frequency.
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71. X₁ · Positive sequence
[X]. Balanced three-phase component with the normal phase order.
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72. X₂ · Negative sequence
[X]. Component with reversed phase order, associated with unbalance.
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73. X₀ · Zero sequence
[X]. Three in-phase components, important for neutral currents.
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74. U₂/U₁ · Voltage unbalance
1; %. Negative-sequence voltage divided by positive-sequence voltage.
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75. I₂/I₁ · Current unbalance
1; %. Negative-sequence current divided by positive-sequence current.
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76. THDu · Voltage distortion
1; %. Total harmonic distortion relative to a specified reference.
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77. THDi · Current distortion
1; %. Current distortion; limits and harmonic range must be specified.
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78. h · Harmonic order
1. Frequency-component index: fh = h·f₁. Amplitude is covered by no. 69.
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79. Δf · Frequency deviation
Hz. Difference between measured and reference frequency.
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80. df/dt · Rate of change of frequency
Hz/s. Describes how quickly frequency changes; needs a defined measurement window.
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81. dip · Voltage dip
V; s. Voltage reduction event, described by residual voltage and duration.
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82. swell · Voltage swell
V; s. Voltage increase event; requires magnitude, duration and threshold.
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83. interrupt · Supply interruption
s; count. Loss of supply under an agreed threshold; count and duration are tracked.
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84. transient · Transient overvoltage
V; s. Short transient event; sufficient instrument bandwidth is required.
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85. RVC · Rapid voltage change
%; s. Change in voltage magnitude defined by the selected measurement method.
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86. Pst / Plt · Flicker
1. Indices of short-term and long-term light flicker severity.
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87. λw · Wavelength
m. Spatial wave period; λw = vp/f.
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88. vp · Phase velocity
m/s. Speed of a constant-phase point in a wave.
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89. vg · Group velocity
m/s. Envelope speed of a narrowband wave packet in the applicable model.
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90. γ · Propagation constant
m⁻¹. Complex parameter γ = α + jβ: attenuation and phase change.
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91. αatt · Attenuation constant
Np/m. Describes amplitude reduction along a propagation path.
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92. β · Phase constant
rad/m. Phase change per unit length.
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93. ηw · Wave impedance
Ω. Ratio of electric to magnetic wave components.
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94. δs · Skin depth
m. Characteristic penetration depth of an alternating field in a conductor.
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95. Γ · Reflection coefficient
1. Ratio of reflected to incident waves at a specified point.
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96. VSWR · Standing wave ratio
1. Maximum-to-minimum standing-wave amplitude ratio.
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97. Zth · Thevenin impedance
Ω. Equivalent network impedance at the chosen connection point.
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98. Ik · Short-circuit current
A; kA. Calculated fault current, determining protection requirements.
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99. Sk · Short-circuit power
VA; MVA. Network-strength indicator at a point; does not express usable load capacity.
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100. X/R · X/R ratio
1. Ratio of reactive to resistive parts of network impedance.
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101. δp · Power angle
rad. Angular position related to power transfer and stability.
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102. Hsys · Inertia constant
s. Stored kinetic energy normalized by rated power.
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103. Kf · Power-frequency characteristic
W/Hz. Slope of active-power change versus frequency change.
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104. Rd · Droop
1; %. Normalized relationship between frequency and controller power changes.
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105. λc · Modal decay exponent
s⁻¹. In exp(λc t), the real part sets decay or growth.
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106. SCR · Short-circuit ratio
1. Short-circuit power divided by the chosen converter rating; a grid-strength indicator.
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107. en · Voltage noise density
V/√Hz. Amplitude spectral density of voltage noise in a measurement circuit.
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108. in · Current noise density
A/√Hz. Amplitude spectral density of current noise.
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109. SN · Noise power density
W/Hz. Noise power per unit bandwidth.
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110. SNR · Signal-to-noise ratio
dB. Describes how clearly a useful signal stands above noise.
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111. L(f) · Phase noise
dBc/Hz. Spectral measure of an oscillator's phase instability.
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112. σy(τ) · Allan deviation
1. Measure of fractional-frequency stability across averaging times.
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113. e · Elementary charge
C. Fundamental constant: exactly 1.602176634 × 10⁻¹⁹ C.
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114. G₀ · Conductance quantum
S. Quantum quantity G₀ = 2e²/h, measured in siemens.
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115. RK · Von Klitzing constant
Ω. RK = h/e²; used in quantum resistance standards.
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116. KJ · Josephson constant
Hz/V. KJ = 2e/h; relates frequency and voltage in the Josephson effect.
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117. Φ₀ · Magnetic flux quantum
Wb. Φ₀ = h/(2e); underlies superconducting measuring devices.
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118. αfs · Fine-structure constant
1. Dimensionless electromagnetic coupling constant, approximately 1/137.
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