Glossary

Disclaimer: API Delevan, Inc. provides the definitions as general reference source of information only and does not assume responsibility for the use or accuracy of the information.

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Air Core Coil, (L_o): An inductive coil that is not wound on a magnetic core. A true air coil consists only of magnet wire wound in a self supporting configuration, this may be in the shape of a single layer or multiple layer. The term is also frequently used to describe coils wound on any non-magnetic coil former such as phenolic or paper tubes.

Air Gap, (L_g): In a magnetic circuit it is the distance, in cm, of non-magnetic length introduced into the magnetic circuit. Most commonly the gap is air, but it can also be non-magnetic shims or spacers. The gap is used to introduce a magnetic resistance, (R) to flux lines thereby reducing the saturation effect of high levels of superimposed current onto the magnetic coil.

Alternating Current, (AC): Current that flows first in one direction and then in the opposite direction, repeated continuously at a rate of so many cycles per second. The cycles per second is called hertz.

AL Value (nH/N²): The inductance index of a core in nanohenries per turn squared.

Ambient Temperature, (° C): The temperature of the environment the inductor will be operating in. Typically this is specified as a temperature range and the maximum specified ambient temperature is used in conjunction with the temperature rise to determine the maximum current rating of the component.

Ampere-Turn, (NI): Product result of multiplying the current, in Amps, by the number of turns in the coil the current is flowing through.

Anechoic: Without echoes.

Anisotropic (Oriented) Material: Magnetic material which exhibits magnetic properties aligned in a given direction.

ANSI: American National Standards Institute

ANSI/IEEE C95.1-1992: Recommendation for limits of maximum human exposure to radiated fields.

Axial Lead Device: A component that has leads emerging from opposite ends of a cylindrical shape and the leads are aligned with body's longitudinal axis.

Back EMF: A voltage opposing the normal flow of current but in particular opposing any variation of a current through a coil.

Balun: derived from "Balanced to unbalanced". A type of transformer used to convert an unbalanced signal to a balanced one or vice versa. It is a device that joins a balanced line (one that has two conductors, with equal currents in opposite directions, such as a twisted cable pair) to an unbalanced line (one that has just one conductor and a ground, such as a coaxial cable).

Bandwidth: with regards to a transformer, that frequency at which the voltage gain has fallen off due to core saturation or high magnetizing current at low frequencies and leakage inductance and distributed capacitance at high frequencies. Bandwidth is an important determinant of transient response and output impedance.

B-H Curve: Used to represent a magnetic materials characteristic in terms of flux density (ß ) and magnetizing force (H)

Bifilar Winding: A method of manufacturing a coil in which two magnet wires are wound simultaneously onto a core, afterwards the wire ends are separated to form two independent windings. Commonly used to increase the magnetic coupling between the windings.

Bobbin: A non-conductive material used to support windings, most commonly used in components devices where the magnet wire can not be wound directly onto the magnetic core.

Breakdown Voltage: The voltage level which causes insulation failure.

Butt-Gap: The gapping of E Cores by equally spacing all three legs of the cores rather than introducing a gap in the center- leg gap only. Twice as much center-gap is required to electrically duplicate a given butt-gap.

CE Mark: European product compliance (conformity) mark.

Center Tap: An electrical connection at the middle point of a winding, the number of turns are equal between the winding start to tap and the tap to winding finish.

Centigrade, (° C): Temperature scale based upon 0 degrees as the freezing point of water and 100 degrees as the boiling point of water. Also known as Celsius temperature.

Certification: (FCC) A procedure that requires submittal of a written application to the FCC that includes an application form, fee, complete technical description of the product and a measurement report showing compliance with the FCC technical standards.

CGS System: Centimeter-gram-second metric system of magnetic measurement. Typically used for smaller number calculations.

Characteristic Impedance: The impedance at which a transmission line transfers its power most efficiently, without reflection or standing wave.

Chip Bead: A generic term for a ferrite component that is produced in a surface mount package.

Choke: Inductor used in an application to impede the alternating current in a circuit. Typically found in power supply filters. These inductors normally are subjected to high levels of DC bias, hence the phrase Power Choke.

Circular mil, (CM): One circular mil is the area of a circle with a diameter of one thousandth of an inch. Used to define the area of magnet wires.

CISPR: International Special Committee on Radio Frequency Interference. (fr. Abbrv. Comite International special des Perturbations radioelectriques)

Clamping: A clamping voltage is the largest voltage allowed by a transient suppressor.

Clearance Distance: The shortest path separating two conductors or two circuit components.

CMRR: Abbreviation for Common-Mode Rejection Ratio.

Coercive Force, Hc (Oersted): The magnetizing field strength required to bring the magnetic flux density of a magnetized material to zero

Coil: Term derived from the act of looping magnet wire around a core. Also used interchangeably to call out an inductor, when used in this manner it typically refers to an inductor for use in RF applications.

Common mode current: The component of signal current that induces electric and magnetic fields that do not tend to cancel one another. For example, in a circuit with one outgoing signal conductor and one return ("ground") conductor, the common mode current is the component of the total signal current that flows in the same direction on both conductors. Common mode current is the primary source of EMI in many electronic systems.

Common Mode Noise: Noise signal that is common to both the converter output and return lines with respect to input common.

Common Mode Rejection Ratio: Ratio of common mode input voltage to common mode output voltage, expressed in decibels (dB)

Common Mode voltage: The voltage that drives directed common mode (noise) currents.

Component: An item which is further integrated into an assembly.

Copper Loss, (Watts): Power lost in an inductor’s windings due to resistance of the magnet wire impeding the flow of electric current, the current can be AC, DC or a combination of both. The loss changes electric energy into heat energy.

Core Constant, C₁ (cm^-1): Summation of the magnetic path lengths of each section of a magnetic circuit divided by the corresponding magnetic area of the same section

Core Constant, C₂ (cm^-3): Summation of the magnetic path lengths of each section of a magnetic circuit divided by the square of the corresponding magnetic area of the same section

Core Loss, (Watts): Sum of hysteresis and eddy current losses in a magnetic circuit due to alternating current.

Core, Magnetic: A structure to provide a lower reluctance path to the flux lines created by the inductor winding. Core shapes are quite varied and may consist of simple cylindrical rods to complex shapes that allow placement of multiple windings.

Coupling: A measure of the amount of flux lines that interconnect between two magnetic devices. In a transformer the design attempts to maximize the flux interconnection between the windings by placing the windings on the same core, while for individual inductors a magnetic sleeve is often placed over the windings to prevent flux lines from emanating from the winding and interfering from adjacent components.

Creepage Distance: The shortest distance separating two conductors as measured along a surface touching both conductors.

Curie Temperature, Tc (° C): The temperature at which a magnetic material loses its ferromagnetic properties and becomes paramagnetic. Returning below this temperature revives the ferromagnetic property.

Current Rating, (Idc): The maximum allowable direct current that can flow within the inductor winding without exceeding the specified temperature rise for the device. Current ratings are not absolute maximums, instead they are dependant upon the maximum ambient temperature and the specified temperature rise.

DC Current Rating: The maximum amount of direct current that can safely pass through the component.

Decibel, (dB): Ratio between two like quantities. Typically applied to for power measurements, but can be also used for voltage & current comparison measurements.

Dielectric Withstanding Voltage, (DWV): Maximum voltage potential an insulating material can be expected to support before breaking down. Typically the DWV requirement is defined with a maximum amount time of application of the voltage, plus a maximum allowable leakage current.

Differential Mode Noise: Noise signal measured between two points with respect to a common point less the common mode noise.

Direct Current, (DC): Steady state electron flow in only one direction.

Disaccommodation, D: The proportional decrease of permeability after a disturbance of a magnetic material, measured at constant temperature, over a given time interval

Distributed Capacitance, (C_d): In an inductor a capacitive effect occurs between winding turns, winding layers, winding turns to core and winding to encapsulation. In an equivalent circuit model this capacitance appears as a capacitor in parallel with the inductor.

Eddy Current: Current induced in a magnetic core which are generated by the lines of flux passing through the magnetic material. The currents generate heat and are part of the total AC loss within a magnetic system.

Effective Cross Sectional Area, Ae (cm²): The practical cross-sectional area of a core available for magnetic flux lines to pass through.

Effective Permeability (m e): For a magnetic circuit constructed with an air gap or air gaps, the permeability of a hypothetical homogenous material which would provide the same reluctance.

EMC: Electro –Magnetic Compatibility. The practice of building electronic devices so that they do not create (or are susceptible to) EMI/RFI.

EMI: Abbreviation for Electromagnetic Interference. EMI is an undesirable characteristic of magnetic fields, the interference is responsible for cross talk between signal lines and radio frequency transmissions. Components used to suppress these fields do so through the use of absorption by turning the unwanted interference signals into heat dissipated within the component.

ESD: An electrostatic discharge with a fast risetime, intensive discharges from humans, clothing, furniture and other charged dielectric sources.

Exciting Current: See Magnetizing Current

Faraday Shield: A metal shield placed between the primary and secondary windings of a transformer to reduce coupling capacitance and output common mode noise. The shield will have only one terminal and is electrically connected to ground potential.

Ferrite: A ceramic like chemical compound of iron oxide and either nickel-zinc, or manganese zinc oxide. The nickel-zinc, Ni-Zn, mixture has initial permeabilities ranging from 10 to 1,500 and are suitable for applications requiring low loss (high Q) at frequencies ranging from 1MHz to 250MHz. The Ni-Zn also displays a high resistivity factor typically on the order of 10⁶ to 10⁷ ohms/cm. Manganese-zinc, Mn-Zn, has permeabilities ranging from 2,000 to 15,000 and are usable over frequencies ranging from 400Hz to 1MHz. Mn-Zn materials have lower resistivity materials in the order of 10¹ to 10² ohms/cm. Normally these materials are used for power applications.

Field Strength (H oersted): The parameter characterizing the amplitude of ac or dc field strength. Field strength is determined by the magnitude of current and geometry of the windings.

Flicker noise: Noise which is greatest at low frequencies and is therefore often called low frequency noise, since it increases as the frequency drops.

Flux (f): Magnetic lines of force which form the magnetic field. The number of flux lines increase or decrease dependant upon the magnetomotive force applied to the magnetic material.

Flux Density: The number of maxwells, or magnetic lines of force, per unit area. In the CGS system unit area is cm².

Frequency, (Hz): The repetition rate of a periodic waveform measured over a one second time period. The more cycles the higher the frequency, measured in Hertz.

Gauss (ß): Unit of magnetic induction in the CGS electromagnetic system. One Gauss is equal to 1 maxwell per square centimeter

Gilbert (F): Unit of magnetomotive force in the CGS electromagnetic system

Hard Magnetic Material: Magnetic material which retains a magnetic field when magnetomotive force is removed from its presence. Permanent magnets are representative of this group of materials.

Harmonic: An integer multiple of the fundamental frequency.

Henry (H): Unit of measurement of inductance. A coil has one henry of inductance if an EMF of one volt is induced when current through an inductor is changing at rate of one ampere per second.

Hipot Test (High Potential Test): A test performed by applying a high voltage for a specified time to two isolated points in a device to determine adequacy of insulating materials. It is often a test to determine if the breakdown voltage of a transformer or inductor exceeds the minimum requirement. See also Dielectric withstanding voltage.

Hysteresis: The property of a magnetic substance that causes magnetization to lag behind the force that produces it.

Hysteresis Loop: A closed curve that shows, for each value of magnetizing force, two values of the magnetic flux density in a cyclically magnetized material: one when the magnetizing force is increasing, the other when it is decreasing.

IEEE/EMC: The EMC Society (professional group) within the IEEE.

Impedance, (Z): Total opposition to current flow, in ohms, of an electric circuit. Comprised of the copper loses associated with the resistance of the magnet wire and the inductive reactance losses associated with the changing magnetic and electric field losses. The summation of the resistive and reactive losses are done via vector addition.

Impulse noise: Noise caused by a single momentary disturbance.

Incremental Current, (dI): The amount of current flowing through the windings of a magnetic device that cause a specified decrease, typically a 5% to 10% maximum limit, in the inductance value of the device. This decrease in inductance is the result of the magnetic core being able to support only a finite amount of flux lines and is the point at which saturation begins.

Incremental Permeability (m D ): The permeability of a magnetic material about a specified operating point and applied H (especially under DC bias). The incremental permeability is expressed as the slope of the B-H characteristic about the given operating point.

Inductance, (L): Opposition to the flow of alternating current in a coil of wire due to the energy stored in the magnetic field of the device. The unit of measure is the Henry.

Inductor: An electrical component generally consisting of magnet wire wound around a magnetic core to introduce inductance into a circuit. The magnetic core may be Phenolic, Powdered Iron, Sendust or Ferrite and can be in many different shapes.

Insertion Loss, (dB): A comparative measurement between the total loss of a circuit with and without the component assembled.

Insulation Resistance: The resistance of an insulating material to the flow of current resulting from an impressed dc voltage. Usually measured in megohms.

Intermodulation noise: Noise emitted not only from the harmonics but also from the sums and differences of the frequencies of an input signal. The number of such intermodulation products can be very large.

Intrinsic noise: Noise generated within a circuit, unlike external noise entering from outside.

Isolation Transformer: A transformer with a one to one turns ratio, where one side is connected to the source and the other to the load. This prevents any DC bias levels present on the source from passing through to the load.

Isotropic (Unoriented) Material: Magnetic material which has equal magnetic properties in all directions.

Layer Winding: The method of winding a transformer or choke where conductors are layered one top of another, commonly separated by an insulating layer.

Leakage Flux: Flux whose path is outside the intended magnetic circuit, measured in maxwells

Leakage Inductance: Self inductance in a transformer caused by leakage flux. This is usually measured by shorting a secondary winding and measuring the value of series inductance across the primary winding.

Litz Wire: A type of magnet wire made up of multiple twisted strands of individual wires formed into a bundle. The wire may have single or multiple bundles and usually is wrapped by a cloth serving insulation.

Loss Factor (tand /m I): The phase displacement between the fundamental components of the flux density and the field strength divided by the initial permeability. Note that a high Q is not desirable in all applications, especially EMI or filtering.

Loss Tangent: The measure of the loss of a magnetic material at high operating frequencies due to the oscillation of microscopic magnetic regions within the material. The loss tangent is expressed as the ratio of the of the imaginary permeability component m " to the real permeability m ’ of the material.

Magnetic Constant (m o): The permeability of free space.

Magnetizing Current: The no-load current in the transformer primary winding that is required to magnetize the core when a voltage is applied. Sometimes called exciting or excitation current.

Magnetomotive Force (mmf): The force required to produce magnetic flux. When electrically induced, magnetomotive force is proportional to (and can be measured in) ampere-turns (SI) or gilberts (cgs). Sometimes known as Magnetic Field Strength.

Magnetostriction: Changes in the physical dimensions of a magnetic material when in a magnetic field, resulting from realignment of its magnetic domains to conform to the field.

Mains-signaling: Using the power supply wires to carry messages, i.e. the reading of meters, usually at frequencies between 3 KHz and 148.5 KHZ . A possible source of interference for any device connected to the mains.

Man –made noise: Noise of human origin such as car ignitions, electric motors, neon signs, fluorescent lights, etc.

Maxwell: Unit of magnetic flux (f) in the CGS electromagnetic system. One maxwell is one line of magnetic flux (f)

Mean Length Turn (MLT): The average length of a single winding turn around the core. In multilayer coils, the length of each successive layer is longer resulting in a longer average turn length.

Microphonics: Noise in an audio system, often caused by flexing of a cable and consequent rubbing of its insulation against its conductors or shield.

MKS System: Meter-kilogram-second metric system of magnetic measurement, used for larger number calculations.

Noise: Unwanted variations in electrical output that are unrelated to the switching frequency.

OATS: Open area test site, sometimes called an open-field test site. The latter could exclude a flat roof.

Oersted (H): Unit of magnetic field strength in the CGS electromagnetic system. One oersted equals a magnetomotive force of 1 gilbert per centimeter of flux path

Ohm's Law: The fundamental mathematical relationship between current (I), voltage (E) and resistance (R). The passage of one Ampere through one Ohm produces one Volt.

Operating Temperature Range: The temperature variation across which a part can be subjected to without degradation to mechanical performance.

Parasitic Capacitance (Cr ): Unintentional capacitance resulting from close physical proximity of two conductors. The copper comprising the wire is separated by its insulation from the core. The capacitance is proportional to area (wire diameter) and inversely proportional to separation.

Parasitic (stray): All AC circuits as their frequency rises acquire stray reactance of two types, capacitive and inductive. Stray capacitance may come merely from two parallel wires and can allow AC to pass. Stray inductance may come from a bend in the wire. DC circuits being without frequency have no reactance, only resistance.

Passive Element: Circuit element that does not actively change the voltage or current waveforms in the electrical circuit.

Permeability, (µ): A measure of a materials ability to support the existence of magnetic lines of flux. It is a ratio of flux density in gauss, (ß), to a magnetizing force, (H), in oersteds. The permeability of air is considered as unity (1).

Permeability, amplitude (m a): The quotient of the peak value of flux density and peak value of applied field strength at a stated amplitude of either, with no static field present.

Permeability, incremental (m D ): This is the permeability derived from the incremental difference of B and H, as given by a small ac signal with a static field, or bias, present.

Permeability, effective(m e): For a magnetic circuit constructed with air gap(s), the permeability of a hypothetical homogenous material which would provide the same reluctance.

Phase Shift: The difference between corresponding points on input and output signal wave forms (not affected by magnitude) expressed as degrees lead or lag.

Phenolic: A non-magnetic material used to provide mechanical support to the magnet wire windings, also provides anchorage for terminal leads if used.

Pink noise: Noise such as flicker noise which varies inversely with frequency.

Powdered Iron: A magnetic material derived from iron oxides. The material is pulverized into extremely small particle size, then sintered to insulate the individual particles prior to being mixed with binders and pressed into magnetic shapes such as bobbins, toroids, axial leaded coil forms, E-cores, etc. By adjusting the iron oxide mix different grades of materials are achieved aimed at providing a magnetic material useable for specific applications.

PPM: Abbreviation for Parts Per Million

Primary turns, (Np): The numbers of turns of magnet wire in the transformer winding that is connected to the signal source.

Primary Winding: In a multiple winding device it is the winding that is connected to the signal source. Only one winding can be designated as the primary.

Q: Figure of merit for an inductor. Measured as a ratio of the inductor reactance divided by the inductance resistance. This is a representation of the energy lost in an inductive device compared to the amount of energy contained in the electrical signal passed through it

Reluctance (R): Opposition to the existence of lines of flux in a magnetic system. Basic unit of measurement is the Rel

Remanence, (ßr): Flux density remaining in a magnetic material after the removal of a magnetic field.

Resistance, (W ): Opposition to the flow of current in a magnet wire, turning electrical energy into heat energy.

Resistivity (r ): The intrinsic property measured in ohm-cm that quantifies a material’s opposition to free electron motion. Resistivity is the reciprocal property to conductivity.

RFI: Radio Frequency Interference. Electrical noise picked up by a receiver that hinders its usefulness.

Ringing: Caused by any electronic device that produces a signal after its input stops. Caused by ineffective circuit damping.

Ripple Voltage: Periodic AC component imposed on the output voltage of a converter.

Rise Time (T r[sec]): Rise time of a square pulse is defined as the shortest time required for the voltage level to change from a "low" state to a high "state". Time is measured between voltage levels 10% and 90% of the "high" amplitude.

Rusty bolt effect: Intermittent contact between metal units, such as fence wire with a fence post, or rainwater guttering at lose joints, producing electronic interference, often with electrolysis between different metals or metals containing impurities.

SAR: Specific absorption rate, measured in watts/kg of body weight.

Saturation: A condition in a magnetic material in which an increase in (b ) will no longer produce an appreciable increase in (H ).

Saturation Current, (Isat): Current flow that causes the maximum number of flux lines to be generated within a magnetic core.

Saturation Flux Density, (ßs): Maximum number of magnetic flux lines that can be present in a magnetic material.

Screened room: A laboratory test room shielded from erratic radio waves, in which electronic equipment can be tested for its EMC and other qualities.

Secondary Turns, (Ns): The number of turns of magnet wire in the secondary winding of a transformer. If multiple secondary windings exist they are identified by a subscript number such: Ns1, Ns2, and so on.

Secondary Winding: In a transformer it is the winding which the load is connected to. Transformers may have multiple secondary windings.

Self Resonant Frequency, (SRF): Within any inductive device a finite amount of stray capacitance exists, known as distributed capacitance, it can be electrically represented as a capacitor in parallel with the inductor. This resultant LC circuit is in essence a parallel tuned circuit and as such the inductance resonates with its own distributed capacitance. The SRF value is important because at frequencies near the SRF the inductor is inherently unstable and is susceptible to extreme variations in its inductive value due to small operating signal frequency changes. If used at operating frequencies above the SRF the capacitive losses predominate and electrically the inductor reacts as if it were a capacitor.

Shielding, Electrostatic: A method of inductor construction that prevents unwanted electrical waves from entering into a magnetic device. Typically the shield is made of a nickel plated brass alloy, or other specialty metal, placed over the inductor and electrically connected to ground. Most effective when used in conjunction with a magnetic shield, it is sometimes referred to as a "tin can".

Shielding, Magnetic: A method of inductor construction that strives to contain the flux lines within the magnetic core, preventing escape to the environment. Certain core shapes like toroids, E-cores, Pot Cores, EP Cores are inherently self shielding since no significant air gap is present within their structure. Axial leaded inductors utilize a cylindrical magnetic sleeve placed over the winding which captures the flux lines.

Skin Effect: Phenomena of high frequency alternating currents to crowd toward the surface of the magnet wire resulting in higher AC loses. Use of Litz Wire reduces this effect.

Sniffer: An instrument for detecting field strength, used mainly to find leaks through shields.

Soft Magnetic Material: Magnetic material which does not retain a magnetic field when magnetomotive force is removed from its presence. Powdered iron and almost all ferrite materials fall into this category.

Split Bobbin Winding: The method of winding a transformer whereby the primary and secondary are wound side-by-side on a bobbin with an insulation barrier between the two windings.

Steel Lamination: Thin pieces of high permeability iron stacked together to make a transformer or choke core. The pieces are often formed in the shape of letters such as E, I or U which also define the transformer configuration. i.e. E/I core.

Swinging Choke: A choke having a high inductance at the lowest load current and a low inductance at the highest current. This results in size reduction versus a choke having a constant inductance to meet both requirements. Typically the magnetic core will be constructed using two separate magnetic materials, a low permeability – high saturation one and a high permeability – low saturation material.

Tap, (winding): An electrical connection at any point in the winding. Typically the tap is identified by the number of turns between the start of the winding and the tap. Multiple taps may occur within a given winding.

Tape Core: A magnetic structure, usually a toroid, whose magnetic core is formed by concentric wraps of a magnetic alloy with thin insulated film between layers.

Tesla (T): SI unit of magnetic flux density (magnetic induction) expressed as 1 weber/square meter.

Test Frequency: The point where the inductance value of the inductor is specified at. This is important since inductors are frequency dependant, i.e. inductance value varies with frequency.

Thermal noise: (also Johnson noise and shot noise) All resistances generate this white noise. Pure inductance or capacitance do not generate this noise.

Toroid: A round magnetic core structure in the shape of a ring, often referred to as a doughnut core due to the similarity in shape.

Transient: Isolated short-term surge or drop in voltage or current.

Transformer: A device used in an electrical circuit that changes a voltage on the primary winding to another voltage level on the secondary winding(s). This transformation is accomplished via a mutual coupling effect between the primary winding and secondary winding(s), with the magnitude of change determined by the turns ratio between the windings. If the primary winding contains more turns than the secondary winding, then the voltage induced in that secondary winding will be decreased by an amount equal to the turns ratio between the primary & secondary winding, a transformer that does this is referred to as a Step Down Transformer. Whereas in a transformer that has a primary winding with less turns than the secondary, then the voltage induced in the secondary winding is increased by an equal amount to the turns ratio, this device is called a Step Up Transformer.

Triboelectric: The transfer of an electric charge between two materials which are rubbed together and then separated, leaving one positively, the other negatively charged, and creating noise. When an insulator touches and then separates from a conductor, the separation and flow of charge leads to noise.

Turns Ratio: Ratio of the number of turns in the primary winding of a transformer to the number of turns in the secondary winding.

Variable Inductor: An inductor that can have its inductance changed by adjusting the physical position of the magnetic core with relation to the winding. Normally this is accomplished through use of a threaded core which can be screwed in or out of a hollow tube, where the winding has been placed upon the tube.

Waveguide: A device used at frequencies above 1 GHz to transmit electromagnetic waves, generally through a rectangular metal pipe, instead of wires or coaxial cable.

Wave Impedance: In an electromagnetic wave of a given frequency the strength of the electric field in volts per meter divided by the strength of the magnetic field in amps per meter.

Weber (Wb): The SI unit of magnetic flux equal to 108 maxwells. The amount of flux that will induce 1 volt/turn of wire as the flux is reduced at a constant rate to zero over a period of one second.

White noise: Noise of uniform power over a wide range of frequencies.

Winding: A conductor wrapped onto a magnetic core or core form.

Winding Area: The cross-sectional area occupied by the magnet wire windings.

Window Area: The cross-sectional area of a bobbin or core that can be filled with a winding.

Winding Length: The allowable length on a core form or bobbin that can be occupied by a single layer winding. One dimension of the core window.

Working Voltage: The specified operating voltage, or range of voltages, of a component, device or cell.