N: number of turns. Using the Neumann integral formula, the expression of inductance is obtained. 5 mm 2 means 2x1. EXAMPLE#1 single layer coil inductor calculator: INPUTS: LOOP DIAMETER = 10 inches, COIL LENGTH = 20 inches, NO. It is the most advance and most accurate method for calculating magnetic field. Only loop inductance can be measured. Here is a Digikey search showing flat-conductor power inductors. Solenoid 6 and 7 were 1 H. Coplanar traces where one trace is the signal and the other trace is the return path apply to this inductance calculator. 1 inch = 0,0254m=2,54cm = 25,4mm. To use this tool, just fill in the required fields and click on the "calculate" button. The pot core inductance is shown on a picture. 2mm) dia. Rectangle Inductance Description. Step 1: In the input field, enter the capacitance, inductance, and x for the unknown. Coil on a ferrite rod. Serway, John W. The mutual inductance M21 of coil 2 with respect to coil 1 is the ratio of the flux through the N2 turns of coil 2 produced by the magnetic field of the current in coil 1, divided by that current, that is, M21 = N2Φ21 I1. The Reactance Calculator will calculate the inductive reactance and the capacitive reactance of a coil or capacitor, and display a live example of how to perform the calculation. L = Inductance in microhenrys (μH) Coil dimensions for calculating inductance. The first thing to know when calculating the impedance of a wire is whether it's a coaxial or twisted pair cable. Use the formula L = R * sqrt(3) / (2 * pi * f). 50 cm in diameter and 4. The inductance of the DIP package connection to the power planes, LDIP, will be calculated with the 'long rectangular loop above a plane' formula (Calculator: Inductance of Wire Above Return Plane). L is the specific inductance in mH for 1000 turns of wire 2. In the model, the wire width of the coil is modelled as constant current-carrying filaments. I selected a 56-pF NPO capacitor for the tuned circuit because it is in the right range, and a dozen or so were in my junk box. Two -Wire Transmission Line The two -wire transmission line is just two long -straight wires running parallel to one another. The transmission line geometries are cross sections and the. This image from AllAboutCircuits, shows various coil cross sections, and their corresponding (approximate) inductance formulae. How do you calculate inductance? Inductance (L) can be calculated using the formula: L = (μ₀ * μᵣ * N² * A) / l, where μ₀ is the permeability of free space, μᵣ is the relative permeability of the material, N is the number of turns, A is. w = wire diameter in inches. Figure 14. Rule of Thumb # 7: In the special case of two flat, wide conductors, adjacent to each other, with a spacing comparable to their line width, the total inductance of either one is just 10 nH/inch. Parallel Wire Impedance, Inductance, Capacitance and Propagation Delay Calculator Results. Use this tool to calculate the reactance or admittance magnitude of an inductor or capacitor at a specified frequency. Select the measurement units (inches or centimeters). inductor or choke on the design stage. built the mutual inductance model between two rectangular filamentary coils by subdividing the RX coil and summing the magnetic flux density of each subdivision. 1 inch = 0,0254m=2,54cm = 25,4mm. l is the length. c. Plug these values into the formula: L = (N^2 * μ * A) / l. Note that the measurement unit may be chosen for the loop diameter and wire diameter. Di = inner diameter in inches. To learn more about the capabilities of EMI Analyst, sign up to access our download area or send us a request . )ISBN: 9781337553292. Dimensions are in meters. 25mm). Any length of wire has some inductance, however, at low frequencies, 1-30 MHz, the added effect of this inductance is usually minimum. The n gauge wire diameter d n in millimeters (mm) is equal to 0. The formulas assume a cable configuration as shown in the figure above. g. The auto-inductance of a coil is dependent on the mutual inductance between each current turn, the self-inductance of the coil’s wire, and the environment surrounding it. Select the box with the geometry that you would like to calculate. On the left side, the LCR meter measures one cable. If it’s too complex, you may try using an inductance calculator to help you calculate the coil inductance. To estimate the mutual inductance, when the gap between the two coils is larger than wire diameter, the thick coil can be denoted by equation of planar spiral coil [ 23 ]. Rectangle Loop Inductance Calculator. The inductance of a flat or ribbon wire (rectangular cross section), can be found using the calculator or the equation given below. To. Corrected Inductance is the Current Sheet Inductance value with corrections for round wire and frequency included. Inductance Calculator. Single layer air core inductor calculator. 1 µH. Loop Inductance Overview. 2808 feet <—> 1 foot = 0. 92445. This formula applies at 'low' frequencies (<30MHz) ) using enameled copper wire. K S is Rosa's round wire self inductance. Description. Figure 14. One trace is the signal and the other is the return path applied to this inductance calculator. The inductance calculated using this tool is the external inductance of a rectangular loop of wire. N is the number of turns. Flat. If the radius (for circular coils) or half the average side length (for rectangular coils) exceeds twice the coil length (F21), the coil is. Following equation or formula is used for inductor calculator for singlelayer coil type. The HCV utilize flat-wire construction with low DCR and high efficiency performance. Flat PCB coils are most often used in the VHF and UHF bands to reduce the size of the device. A is the cross-sectional area of the coil in square meters (m 2)L = √ [(L 1 *Sin(X)) 2 + (L 2 *cos(X)) 2] - aggregate inductance of coil Inductance in µH, dimensions in inches. k. The inputs. While this is a “round wire” formula, it may still be applicable to. The formula to calculate impedance is: Where. The electric current produces a magnetic field around the conductor. L cap = 3. To calculate the values, just select or enter the AWG size and. The above are rough calculation only. 2. Choose a calculator to tune your PCB design. Available Winding Area of the Core: W A c. Model accounts for proximity effect of closely spaced wires. Dimensional units:. Lastly, to calculate the inductance, use the following formula – L = R x sqrt (3) / (2 * pi * f). Choose units for a and W. Any material that has current flowing through it and produces a magnetic flux has inductance. Wire Self Inductance Calculator. The compact flat wire inductor is designed for efficiency. Planar coils are mostly used in high frequency applications and designed as tracks on a circuit board. Air Core Flat Spiral Inductance. The hidden assumption is that the wire is really part of a loop! For example, take an axial lead resistor, mounted to a. Calculate the inductance (L) in henries (H). The additional formulas: Where D1 D2 are the outer and the inner diameters of the toroidal coil-former, dw is the wire diameter. resistance ratio using formula 2. Straight conductor. This tool calculates the inductance of a common object in electrical engineering: two parallel wires. µ r = Relative permeability (dimensionless) µ 0 = 4 π x 10 -7 H/m (permeability of free space) 1 meter = 3. 2 µH to 10 µH. 2：Conductor thickness shall be smaller than conductor width. 25664 × 10-6 T·m/A. Figure 14. Inductance is a property of electrical circuits that causes a voltage to be induced in a conductor when the current in the conductor changes. Dimensions are in meters. The impedance ZL of an inductor of inductance L, in complex form, is given by ZL = j XL. The larger the space between corresponding circuit conductors, the larger the inductance. The inductance for the two wire inductance might be useful in measuring the inductance for a signal and ground on a ribbon cable. The approximate formulas used to calculate the inductance are provided along with restrictions on the relative size of the various parameters. There are some advantages to using a microstrip transmission line over other alternatives. This calculator based on Rosa's straight wire self-inductance formula. Enter at least any two input values and click calculate to solve for the remaining values. A flat spiral coil is a type of an air core inductor usually incorporated in the primary of a tesla generator, RFID tag, and proximity detectors. It is independent of the potential difference between the conductors and the total charge on them. To calculate the number of turns (N) required to make any specific inductance,This calculator makes use of standard bobbins in Fair-Rite's # 77 material - so frequency is limited to about 10 MHz, depending on the winding. a primary tank capacitor or topload capacitance to find the resonant frequency of the LC circuit. 75 instead 2. This planar spiral coil inductor calculator determines the inductance of one-layer circular, square, hexagonal and octagonal planar (flat) spiral coils, which are often used in near-field communication (NFC) and radio frequency identification (RFID) tags. Pieper X z 50u 150u 500u 50u 100u 350u 450u 200u 300u l1 l2 l3 l4 l5 P1 P2 P3 P4 P5 P6 r/u dz/mm G (S/m) L_ADS/pH l_wire/um L_straight/pH deviation z 0 200 300 300 200 0Calculate the height of the object by the length of shadow. Visit to learn more about our other electrical engineering tools. Fotopoulou and Flynn discussed a novel analytical. If you don’t already have one, consider getting a breadboard. At 20khz the reactance is approximately 0,44 ohms. e. Parallel Wire Inductance Calculator. Many conductor properties are frequency dependent and dynamically affect electromagnetic characteristics of circuitry and systems. This is used to calculate the inductance and the energy stored. number of turns. Inductance. Lcoax ≈ μ0μrL 2π ln( D d) L c o a x ≈ μ 0 μ r L 2 π l n ( D d) Where: Lcoax L c o a x = inductance of the coaxial cable in henries (H) μ0 μ 0 = permeability of free space = 4π×10 −7. Assumptions and Limitations Dimensions are in meters. ηo η o = wave impedance. The permeability of air is 1 for all practical purposes. 2Loge 2S d (Hm/Km) Where: L = Inductance of cable in (Hm/Km)Self and Mutual Inductance of a Pair of Parallel Rectangular BarsOnline AC magnetic field calculator for solenoids and coils. The capacitance calculated using this tool is the capacitance between a flat conductor and two equidistant ground planes. D D = diameter of the wire. Maxwell equation: a = d/2 is the radius of the wire cross-section, half of the wire diameter (m) However, in the Coil32 calculation of the loop inductance is carried by a simple empirical formula, which was first brought by F. Step 2: To calculate the resonance frequency, click the "Calculate x" button. Flat Spiral Coil: The inductance of a flat spiral coil can be determined by entering its dimensions in the boxes above. 25*rw, where r w - wire radius. In the past it was thought that the secondary coil wire length should match the quarter wave length of the Tesla coil's resonate frequency. 2r. The round-wire geometries are loops of wire with various shapes. The formula for calculating the self-capacitance of an air-core single-layer solenoid is: Where. The inductance calculated using this tool is the inductance of the loop bounded by the two coplanar flat conductors. Alternatively, you. The effective diameter Deff obtained from here is used to calculate the inductance of the single-layer helical coil: where: μ: permeability of the coil core. W. Let the width of the plates be b b, the distance between them a a and length l. Related Products: Magnetics, Transformer Misc Flat Spiral Coil: The inductance of a flat spiral coil can be determined by entering its dimensions in the boxes above. The magnetic field strength depends on the magnitude of the electric current, and follows any changes in the magnitude of the current. Use our free online app Wire Self Inductance Calculator to determine all important calculations with parameters and constants. Step 2: Fill in Dw for wire. resistance is, therefore, 1. H = Factor corresponding to coil length/diameter ratio. The larger the mutual inductance M, the more effective the coupling. To find out how much inductance a coil has, do the following: Step 1: Enter the coil radius Rc or the coil diameter Dc (in Advanced mode). The Magnetic field linking the Ground wire is Zero and hence the Inductance of the Ground conductor is Zero. The minus sign is an expression of Lenz’s law. Air Core Inductor Designer / Calculator. resistance of the Litz wire construction using formula 3. 5Turns 25-100MHZ. 11. Overview. This correction, in microhenrys, is added to the inductance. com Wire Self Inductance Calculator. Below you see a transmission line consisting of 2 parallel wires. 2. w = width of winding (in inches) N = number of turns. L is the inductance, so you need the resistance (R) and the. 000uH to 100. The inductance of a wire loop is a common textbook example of a circuit with inductance. Elliptical Integrals of the First Kind Calculator. ϵr ϵ r = relative permittivity of the dielectric between the plane (s) and the wire. The formulas assume a cable configuration as shown in the figure above. Files: coil. Studying transmission lines I am confused about a "missing" factor of two in the formula L =μ0a/b L = μ 0 a / b for the inductance per unit length of two "infinite" parallel sheets. The flux linked by the circuit is the flux found in the region between the two wires. Assumptions and Limitations Dimensions are in meters. W. 99 – £ 29. 375 uH to 3. Table of Contents. A is the cross-sectional area of the toroid core. Effective equivalent circuit; effective equivalent circuit: effective series inductance at the design frequency from Corum’s sheath helix waveguide formula, corrected for field non-uniformity and round wire 1,3,6,7 (L_{ ext{eff,s}}) µH: effective series reactance of the round wire coil at the design frequencyCoil Inductance Calculator. From this result, we see that the trace inductance depends on: Trace thickness (or copper weight)In Equation 14. Dimensions are in meters. Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. 4. Weaver’s article Numerical Methods for Inductance Calculation is used for calculations of. In accordance with the Ampere's Law, we can calculate the magnetic flux density in the core at an arbitrary distance r from its central axis. Wire is assumed to have circular cross section. Always bear in mind that there is a tolerance on the stated AL value of a core. A wire loop creates inductance. 132 s 9. W. ТThus, to calculate the inductance of a Tesla's flat spiral coil by the Maxwell's method. Total inductance of series-connected inductors is equal to the sum of the individual inductances. Both round and flat variants of wire braid can be found under a few different call numbers, including AA59569 Mil-Spec braid which was formerly regulated b the QQ-B-575 military specification. EEWeb offers a free online twisted pair impedance (transmission line) calculator. I also have a formula for the AC resistance of a solid wire derived in the book Electromagnetic compatibility Handbook by Kaiser and is very simply derived as follows:. The inductance of a solenoid can be stated as. Some people call it "magnet wire". This calculator takes into account your fixturing length, cable length, and the presence of shields and will return an estimate of the capacitance a test will see from one wire to all other wires in the cable under test. 0uH. Single layer air core inductor calculator. Dimensions are in meters. Description The inductance calculated using this tool is the inductance of the loop bounded by the two biplanar flat conductors. Measuring Inductance Range: 0. Stripline Inductance Model Inductance of the loop bounded by the center conductor and ground planes is: Units: Henries. 7 mH, 3. At high frequencies, a real inductor is usually modeled as the LRC circuit shown in the figure. All conductors have inductance. H H = height of the wire above the plane. Find magnetic permeability and inductance factor of an unknown ferrite toroid core. Internal self inductance; External self inductance; Mutual inductance; Any capacitive reactances; For now we can ignore wavelength as it pertains to cable length as my specific question pertains to frequencies less than 100kHz and wire lengths less than 100m so these effects can be ignored. Grover} IvductanceofPolygonalCoils. 7 shows several types of inductors commonly used in circuits. Yours calculated 3. 7. 62) 19. Another advantage of ribbon over round wire bonding is the better mechanical loop stability of ribbon bonds which can achieve lower loop angles and lower loop heights than round wire bonds. The n gauge wire diameter d n in inches (in) is equal to 0. The inductance of solenoid follows then from the following equation: L = µ₀ × N² × A/l. Internal inductance is not included in this model, but may be calculated using the Wire Internal Inductance tool. 66. 005in times 92 raised to the power of 36 minus gauge number n, divided by 39:. Note that the input inductance should be in nano henries (10 -9 H). If, on the other hand, a < δs or merely ∼ δs, then current density is significant throughout the wire, including along the axis of the wire. Many magnetic field coupling circuits, such as chokes and transformers, take advantage of a coil’s magnetic storage properties. Enter the coil diameter (form diameter + wire diameter - see diagram). Because the material is working well under 48 twists. 001N2D/ ( (228D/2) + 254l) Where: L is the inductance in henry's. Parameters . Table 6 shows the cross-section area for a round wire versus. Flat spiral air core coil inductor design calculator solving for inductance given wire coil number of turns, core material permeability, coil area and average coil length. Input the values into the formula and calculate the self-inductance. Wire can be. Loop length and width must be greater than the wire diameter. Enter the width of the conductor:imity factor Φ. The inductance of a wire loop is a common textbook example of a circuit with inductance. Select the Conductor Material: Enter Data Aluminium Copper Gold Nickel Silver. ductance". Non-inductive bifilar winding Nikola Tesla's flat inductive bifilar coil. I selected a 56-pF NPO capacitor for the tuned circuit because it is in the right range, and a dozen or so were in my junk box. Frequency: You must enter a frequency for the calculator to work Calculating inductance: To calculate the inductance, input the capacitance into the appropriate cell Calculating capacitance: To calculate the capacitance, input the inductance into the. 419µH for an upper and lower coil) = 142. This calculator computes the inductance of a microstrip etched on a PCB. The permeability of a vacuum is exactly 1. The figure below shows the overall inductance over frequency for a 1m single wire over ground plane in the unit Henry. The magnetic field strength depends on the magnitude of the electric current, and follows any changes in the magnitude of the current. The loop self inductance, distributed per inch of circumference, is roughly 150nH / 6 inches, or 25nH per inch of circumference. Calculations provided on this page are a simplified subset from EMI Analyst models. Regards JimFlat Spiral Coil. (We are only concerned with the external inductance here. A microstrip is a flat conductor separated by an insulating dielectric from a large conducting ground plane and is mostly manufactured from a printed circuit board. As such, the design of the series inductance must be carefully chosenMeasure capacitance and inductance of a two-wire parallel transmission line. inductance of the loop can be expressed as the sum of the inductances of the two half-loops above the top plane and the inductance of the loop between the planes. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. The wire may be flattened to various aspect ratios, with. The inductance calculated using this tool is the external inductance of a rectangular loop of wire. It is possible to calculate L for an inductor given its geometry (size and shape) and knowing the magnetic field that it produces. Introduction . The round-wire geometries are loops of wire with various shapes. calculations for metric conversionsThe IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. Scientific Calculator. The actual bus bar design parameters may need to vary according to detailed structural requirements, working conditions etc. The inductance allows one to understand the amount of energy that can be stored in magnetic fields. This tool calculates the inductance of a common object in electrical engineering: two parallel wires. It is important to note that in industry we can find that some differential pairs are routed this way for a strong coupling, but the actual return for the signal is on a. Let's calculate using 9 gauge wire with descent insulation. EEWeb have a free online Coil Inductance Calculator for calculating the inductance of a coil for different configurations of wire size and positioning. coil. 7. 2. Some people call it "magnet wire". Measurement accuracy:1%. The equation of the circular spiral coil, motivated by the Archimedean spiral coil can be described by. Click to enlarge!- litz wire lay direction. Per se, partial inductance of a single wire cannot be measured. S. μr μ r = relative permeability. According to Eq. Input (number of turns) N = (length of one side) W = (wire radius) a =. Effective equivalent circuit; effective equivalent circuit: effective series inductance at the design frequency from Corum’s sheath helix waveguide formula, corrected for field non-uniformity and round wire 1,3,6,7 (L_{ ext{eff,s}}) µH: effective series reactance of the round wire coil at the design frequencyThis gives a lay length of 41. Ferrite E-core online calculator. Flat Wire Inductor For a flat wire, ribbon or PCB track, showing the formula used. r is the coil radius. d d = coaxial cable inner diameter. One exception is the solenoid, because it has a very uniform field inside, a nearly zero field. Wheeler’s spiral formula is 1% accurate for c>0. Phased-array radiofrequency (RF) coils are commonly used for signal reception in magnetic resonance for their large spatial coverage, typical of volume coils, and for their high signal-to-noise ratio, usually associated with surface coils. Also, these calculators allow calculating just a ready-made coil. Wire Self Inductance Calculator Formula. According to Eq. design parameters resulting in the required inductance must be found. Calculates the Inductance of a single round wire of common conducting materials using the formula and data referenced below. 3. This tool is primarily used to calculate coil inductance and volume using coil parameters. Inductance of flat ground strap decreases as length-to-width ratio is decreased. Where: Lcoil L c o i l = inductance of the coil in henries (H) μr μ r = relative permeability of the core (dimensionless) μ0 μ 0 = permeability of free space = 4π × 10−7 4 π × 10 − 7 (H/m) N N = number of turns. Some of them were designed to be used in static solid-state NMR probes operating at 1 H frequencies of 300 and 600 MHz, see Solenoid 1–5 in Table 1, which were tested with a inductance measurement circuit []. Yes, I'm using a flat trace circuit, in an equation for "round wires". The other calculators I tried online were estimating from 2. Can someone please help I need to find the coil inductance of 1650 turns 32 GA wire with 52. In this tool, the variables required are length and wire diameter. Many radio fans in the constructions as chokes apply the multilayer coils with the. . This is difficult in most cases, because of the complexity of the field created. 2. Inductance is the ability to store energy in a magnetic field, and coils are a common way to create inductance. Calculate the inductance using a mathematical formula. Due to its geometry, the coaxial cable impedance requires you to know the inner wire's diameter and the outer shielding. Wire Inductance. length. The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). Any length of wire has some inductance, however, at low frequencies, 1-30 MHz, the. A flat spiral coil is a type of an air core inductor usually incorporated in the primary of a tesla generator, RFID tag, and proximity detectors. With the advent technology of multilayer PCB, the multilayer coil appears. 4. The formula for calculating the Inductance of a cable is given by: L = K + 0. Conductors is assumed to have zero thickness. The geometrical mean distances for a round conductor with radius r, for a flat wire of width a, and for a square wire with side b are: R e . 11. This Coil Calculator is a professional and easy-to-use electrical tool for electrical engineers and designers. Conductors are assumed to be embedded in a homogeneous medium having permittivity and permeability. In the plugin square_loop following formula is used: where: L - inductance (μH); a, b - loop sizes from center to center of wire (m); r - the radius, half of the wire diameter (m)Enter inductance value (making sure to enter the units correctly as nH,uH or mH) and enter the AL value of the core. Z0ws = ηo 2π√ϵr ⋅ln( 4H πD) Z 0 w s = η o 2 π ϵ r ⋅ ln ( 4 H π D) Where: Z0ws Z 0 w s = characteristic impedance of a wire stripline in ohms (Ω) D D = wire diameter. Matching T Attenuator Updated calculation of bandspread or tracking capacitors. A long solenoid with length l and a cross-sectional area A consists of N1 turns of wire. Where r w - cross-section radius of the wire. Inductor calculator equation and structure for singlelayer coil type. Ground planes are assumed to be perfectly. 3 mm, the inductance of the loop between the planes tends to be small relative to the connection inductance above the planes. Assumptions and Limitations. In order to do away with the ambiguity of an inductance range result, a novel, naive approximation formula was deduced. Description The inductance calculated using this tool is the inductance of the loop bounded by the flat conductor and the ground planes above and below the conductor. The A. The use of a magnetic core is ineffective. For very high frequencies the inner inductance gets zero and the overall inductance tends to its outer inductance. according to Rosa, 1,4,5 • A round wire mutual-inductance correction factor k. Touch the red wire to the exposed end of the resistor and the black wire to the opposite end of the inductor. Parasitic inductance is an unwanted inductance effect that is unavoidably present in all real electronic devices. The inductance of a rectangle loop has three geometric variables: W – rectangle long side; h – rectangle short side; d – wire diameter; Rectangle Loop Inductance Model. Units for M are (V ⋅ s)/A = Ω ⋅ s, which is named a. CiteThe choices of wire are solid, stranded, foil, and Litz wire. Velocity factor is a fractional value relating to a transmission line’s propagation. I is the current intensity, in Ampere. Inductance is going to be around 3500 nh for 10 feet. Finally, we have two equations for the inductance of microstrip and stripline traces. (2) θ = 2 π N. Parallel Wire Impedance (Zo) = Ohms. Benefits include greater wire density in the gap, and a single layer of flat wire has less inductance than two or more layers of round wire. "Coil64" is a free coil inductor calculator, that allows calculating: single-layer and multilayer air core inductors, toroidal air core coil inductance, inductors on ferrite rings, in pot core, flat coils on the PCB, and also LC tank parameters. Calculating limitations: The winding pitch cannot exceed the doubled wire diameter; Coil diameter cannot be greater than the doubled diameter of the rod ; Winding length should be less than 3/4 length of the rod; When the coil is shifting it should not reach the edge of the core 1/8 of its length; The initial magnetic. C. However on high frequencies there are some features. ex. Coil Inductance Calculator. Conductors are assumed to have zero thickness. It is more difficult to calculate the mutual inductance of the rectangular coils with lateral or angular misalignment. Coplanar Capacitance. Example 1: Find the inductive reactance of a coil that has an inductance of 320 µH (0. eff. Wire sizes, AWG # chosen to meet current specification. Inductor Design Spec’s I L r L L} AWG # Choice for inductor wire windings. Calculate the D. Broadside coupled traces are on adjacent planes and the return is identical to the trace in width and length. 2. Round wire corrections are not required for single turn coils. 199 2 6. to D. Choose units for a and W. l is the Length of the conductor in mm. The size of the loop is determined by a, the radius of the loop. Use the formula C = ε · A/d to find the capacitance C. A user enters the inductance, L, and the frequency, f, and the result will automatically be calculated and shown.