What is Coil: Definition and 900 Discussions

A coiled coil is a structural motif in proteins in which 2–7 alpha-helices are coiled together like the strands of a rope. (Dimers and trimers are the most common types.) Many coiled coil-type proteins are involved in important biological functions, such as the regulation of gene expression — e.g., transcription factors. Notable examples are the oncoproteins c-Fos and c-jun, as well as the muscle protein tropomyosin.

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  1. L

    Permeable coil cores; what's actually happening?

    In descriptions of how an electrical transformer works, I've seen it said that the permeable core "conducts a magnetic field" or "allows magnetism to pass through better than it passes through air", but isn't that description misleading? Isn't it really the case that the permeable material's...
  2. P

    What exactly does the capacitor do in a Tesla coil?

    In all tutorials I have read on tesla coils, they have said to use a capacitor spark-gap configuration, to create a tank circuit. I want to know exactly what this means, and what is its purpose. I am not going to build a Tesla coil, I am nearly just interested in the science of it.
  3. ReidMerrill

    What is the Correct Method for Finding Induced EMF in a Coil?

    Homework Statement A 4.0 cm diameter coil (1000 turns) is at rest in the XY plane. The magnetic field in this region of space is given by B=(0.30i + 0.50t2 k) What is the induced EMF in the coil at t=2.0 seconds Homework Equations ε=dΦ/dt Φ=ABcosθ The Attempt at a Solution ε=[/B]d/dt(...
  4. C

    How to Calculate N of a Solenoid: Understanding Turns per Meter

    i'm confused with N , it says that is the number of turns per meter , but is the meter the length of the wire or the coil height ?
  5. Shadow-Shocker

    Building a musical tesla coil,

    What is the general cost for building a tesla coil. I already have a PVC pipe and wiring, but I know I need a board, power supply, coil, led lights, capacitors, resistors, and semi-conductors, etc. I know there are some things I am missing and I am on a budget. If there are any other supplies...
  6. DevonZA

    Calculating Instantaneous Current in an Inductive Circuit with Delayed Switches

    Homework Statement In the inductive circuit shown in Figure 2, the switch S1 is closed 0.75s after switch S2 is closed. Calculate the instantaneous current in the coil 1.5s after switch S1 is closed. Homework Equations T=L/R I=V/R The Attempt at a Solution When S2 is closed: T=L/R =2.4/7.2...
  7. L

    Magnetic field in rectangular coil (not solenoid) Amperes law

    Homework Statement I have a rectangular coil with length L and the cross-section's sides has length a and b (b>a). A wire is tightly wrapped around N times. Calculate the magnetic field inside the coil. Homework Equations The problem I have is that in class we were taught how to calculate...
  8. E

    Electrical energy converted to heat in coil

    Homework Statement Given a coil with N turns, a radius of r, a resistance of R', and an induced current i'(t) running through the coil, determine the totale energy converted to heat in the coil for t>=0.EDIT: The circuit on figure 4 consists of a resistance R and a capacitor with capacitance...
  9. D

    Rotating Coil in Magnetic Field

    Homework Statement [/B] Magnetic field values are often determined by using a device known as a search coil. This technique depends on the measurement of the total charge passing through a coil in a time interval during which the magnetic flux linking the windings changes either because of the...
  10. D

    Magnetic Field of Rotating Coil

    Magnetic field values are often determined by using a device known as a search coil. This technique depends on the measurement of the total charge passing through a coil in a time interval during which the magnetic flux linking the windings changes either because of the motion of the coil or...
  11. C

    B-field to create average emf in rotating coil

    Homework Statement A 0.300 m radius, 487 turn coil is rotated one-fourth of a revolution in 4.17 ms, originally having its plane perpendicular to a uniform magnetic field. (This is 60 rev/s.) Find the magnetic field strength needed to induce an average emf of 10,000 V.[/B]Homework Equations E...
  12. Chris Fuccillo

    Does a coil with CW and CCW turns split its B field?

    Single Electro magnet with split field Single core with separated counter clock wise and clock wise turns My question: I’m not worried about field strength at the moment, I am just trying to make sure that the field will develop in this manner? Note: Please see picture. If you take a ferrous...
  13. Benoit

    Tension in a Spring: Find the Difference

    Imagine a spring that has its two ends attached to a wall at the same height. The spring will adopt a kind of a ''U'' shape (maybe a parabollic shape would be more precise). Why are the coils near the wall more distant from each others than the coils at the middle of the spring ? I think it is...
  14. E town

    How to Build a Pulse Coil for a 13,000 Gauss Magnet?

    Hi Guys, I'm new on the forum so forgive me if this has been posted before. I'm kindly looking for some advise to build a pulse coil set up to spin a 13,00 gauss 1" diametrically magnetized magnet. I was hoping to use 120 volt rectified dc or the highest voltage that has readily available...
  15. A

    Inductance of Square Coil Antenna on PCB

    Hey guys, I am trying to design an Inductive Square Antenna Coil that will be milled onto my PCB. I am slightly confused when it comes to the matching circuit. To my understanding the matching circuit is there to have the same impedance value of the antenna, correct? So my matching circuit...
  16. endiewibowo

    I What is Returning Loop of Rogowski Coil?

    I read on a source from a paper from John D. Ramboz that explains: The incremental pitch-advancement of the coil's helical winding sums over its circumferential length to create an undesirable one-turn loop normal to the axis of the coil (the plane of this loop is parallel to the surface of the...
  17. B

    What are the best resources for learning about E&M as a beginner?

    For research purposes, what would be the result of Electrical flow or magnetic strength if an Insulated copper Coil were wound around a pice of copper pipe?
  18. L

    Average back emf induced in coil

    Homework Statement The coil in a loudspeaker has an inductance of L = 56uH (or 5.6 x 10^-5 H). To produce a sound frequency of 20 kHz, the current must oscillate between peak values of +2.2 A and -2.2 A in one half of a period. What average back emf is induced in the coil during this variation...
  19. uzi kiko

    Impedance matching and tuning of RF coil

    Hi everybody. I am trying to understand the concept of impedance matching and tuning of RF coil. As far as I understand there are 2 stages: At the first stage I should match the coil to the source (Let's say with L network method) and the second stage is to tune coil to the desirable frequency...
  20. uzi kiko

    Impedance matching and tuning RF coil

    Hi everybody. I am trying to understand the concept of impedance matching and tuning of RF coil. As far as I understand there are 2 stages: At the first stage I should match the coil to the source (Let's say with L network method) and the second stage is to tune coil to the desirable...
  21. M

    Does diameter of air coil in electromagnet affect strength?

    The title is explanatory. I know that an iron core yields a stronger electromagnet. What if you have an electromagnet with an extremely tiny air coil relative to its volume? Does the small air coil diameter effect the electromagnet?
  22. B

    Ignition coil HV pulse on oscilloscope?

    Hi all, I've been using a HV step up transformer (10kV-20W on secondary) lately and I'm wanting to look at the HV pulses on an oscilloscope. The coil is isolated from ground. I know connecting a probe directly to it is dangerous and would ruin my scope. I want to use a differential probe but...
  23. Z

    Is the coil the only viable shape for an electric engine ?

    Hi, I'm an hobbyist right now I'm into electric engines, simple engines for low voltage and low current applications; I have noticed that there are many variations about how and what an electric engine can do even considering only DC motors, but basically all the engines that I have examined up...
  24. B

    Generating EMF in a Coil with a Bar Magnet - 65 Characters

    Exactly what and how generate EMF in a coil when I move a bar magnet in it? How the changing magnetic field makes electrons to move? (I mean quantum mechanically.) As I read somewhere when I close the circuit (put a load, a LED for example on the coil) the generated current in the coil will be...
  25. R

    How to design coil terminals for maxwell3D transient?

    In magnetostatic simulation model I design the winding as a volume of copper and assign a single plane on the volume of copper as current excitation terminal to define the winding current value and its direction. In transient model when I am creating coil terminal for a winding, I need to...
  26. B

    Drive a 12 Ohm, 50mH Transformer Coil with 12V @ 1A

    I have a signal generator that is used to generate 12kHz square waves. I want to use my signal generator to drive a transformer primary coil. My coil has 12 ohms resistance, 50mH, and will have 12V applied to it @ 1A. Can I buy a circuit to drive the coil from the signal generator pulse or do I...
  27. K

    Electromagnetics: Non-Symetrical coil with external iron

    Hello, and thanks for looking at my question. For starters, this is NOT a homework question, or a question I will receive any credit for except maybe a "hey, cool". The level of difficulty is roughly a junior-year Electromagnetics class homework quesiton, I suppose? My Question is rather...
  28. M

    Is it possible to detect current ramp-up to DC with a coil?

    Hi, I am thinking of ways to detect when an electrical device is turned on and off without actually touching or modifying the existing circuitry. More specifically, I have a hand held device powered by 2 x 9V batteries and with 2 electrodes connected through leads and plugs to sockets on the...
  29. Guidestone

    Why don't electrons jump between the turns of a coil?

    Hey guys. I just want to know why electrons in a coil always follow the turns instead of jumping from one turn to another. I mean, in many cases the turns are very close to one another. Also, if I'm not mistaken, electrons travel the shortest distances. Thank you!
  30. F

    A coil moves into a magnetic field

    Homework Statement A coil, made up of 1850 loops, is inserted in an electric circuit and has a resistance of 45,0Ω. The area of each loop is 4,70⋅10^(-4) m^(2). The coil moves from a region where there's no magnetic field, to a region where the magnetic field is present. The normal to the coil...
  31. L

    Average back emf induced in coil

    Homework Statement hey! I saw you've answered this question before... Hi, I would appreciate any help with the following: The coil in a loudspeaker has an inductance of L = 112 microH. To produce a sound of frequency 40kHz, the current must oscillate between peak values of + and - 4.4 A in...
  32. Weightofananvil

    Engineering Magnetic circuits with air coil question

    Homework Statement a magnetic circuit with a coil of 500 turns and a core of sheet steel has an air gap of 1mm. the sheet steel has a mean path length Lss = 0.25 m and a cross section that measures 1cm x 1.6 cm. (assume: u air = u0(not) = 4pi x 10^-7 wb/(Am). determine how much coil current is...
  33. T

    Simulation with Spice to get coil and caps values

    Hi, as I am in need of Low- and Highpass filters i would like to simulate my circuit using LT-Spice. I hope that i can get optimal caps and coils values like that. So i simply started to build my pi-network lowpass filter in LT-Spice and got the simulation results (please check the picture in...
  34. W

    Wanted: Looking for a helmholtz coil in Brisbane, QLD AUS

    Hi guys, I'm a typical nerd that wanted to do an at home science project but don't want to spend lots of money on this coil. I would love to borrow/rent one if someone could help me. Otherwise if someone new a cheap supplier that i could get one off? It looks like either of these pictures :)...
  35. Syed Khairi

    Optimum Length & Turns for a Search Coil of a Fluxmeter

    Hello, I'm investigating the relation of the length and number of turns of a search coil of a fluxmeter (measure magnetic flux). I got to an equation B= qR/nA where q is the quantity of charge passed through search coil R is the combined resistance of search coil and fluxmeter n is the number...
  36. B

    Coil Winding Direction: Clockwise vs Counter-Clockwise

    I am wrapping a transducer coil and had a question with the winding direction. Let's say that I am wrapping the wire around a bolt in a clockwise direction. After I reach the halfway point of the wire, if I then reversed the direction I am winding to counter-clockwise, what would it do? I am...
  37. S

    Why do transformers use AC currents in the primary coil?

    Hello. If we assume an ideal transformer, why do we use a.c current in a transformer? I've searched and answers are that we need a changing electric current to produce a change in magnetic flux, using Ampere's law. However, Faraday's law states that a voltage produced a changing magnetic flux...
  38. R

    Calculating Inductance of a Solenoid with Multiple Isolated Loops

    I found this formula to approximate the inductance of a coil of wire. But what if a solenoid were composed of N separate loops, where each loop of the solenoid is connected to its own battery? That is, what if the solenoid had the same number of loops and the same geometry, except that each loop...
  39. E

    Using a bimetallic coil to turn a pulley

    Hello, I am looking at the possibility of turning a pulley using a bimetallic coil embedded inside. How can I calculate the thermal "spring constant" of the coil, as a function of geometry and material properties? Does anyone know of devices with similar actuation mechanisms? thank you.
  40. Salvador

    Toroidal coil rotating magnet

    there is a toroidal coil , a magnet rotates in the middle of the coil , I wonder what happens when first the magnet that rotates is a permanent magnet , second case if the magnet that rotates is a electromagnet supplied with a certain frequency AC current? I wonder what kind of output we see on...
  41. Davian Francis

    What is the Optimal Water Flow Rate for Designing a Helical Coil Heat Exchanger?

    really need help in designing a helical coil HE. i know i must first do an energy balance to find heat rate.but what next?to find the area needed and the number of turns etc
  42. J

    Calculating Average EMF in Two Coils on a Ferromagnetic Core

    Hey guys been trying this question for a while now and i just can't seem to find any equations which link the two coils to find average EMF and also the final current I2. I am new to electrical so still learning any help is much appreciated, thanks! Two coils, A and B, are wound on the same...
  43. M

    Making Steel Wheels Magnetic for Model Train Track

    I have a project I'm working on where I need to have a model train be able to have an electromagnet hold its wheels to the track -- so that it can go "upsides down" and resist derailment. I'm making the wheels and the track -- so all options are on the table. If I used a steel track (say...
  44. Salvador

    Coil loop with a magnet through it produces AC or DC?

    Here is my misunderstanding , for the example let's ignore resistance losses , say i have a infinite length of coil , and an infinite strip of magnets passing through that coil, each magnet separated by some distance from the next one , the strip of magnets move through the middle of the coil ...
  45. B

    Will a DC to Pulse Width Modulator work for SS Tesla Coil?

    I am making a small solid state tesla coil. I have the secondary coil, toroid and primary coil but am not sure what to do for a control circuit. I was planning on using two 9 volt batteries for power. Would a DC to Pulse Width Modulator work? This is the one I was thinking of -...
  46. J

    Why Is the Cross Sectional Area of a Coil Used in Calculating Flux Linkage?

    Flux linkage in a wire coil is given by BANcos(theta) with B being flux density, N being the number of turns in a coil and A being the cross sectional area of the coil and theta being the angle between the normal to the plane of the coil and the magnetic field. Is anybody able to explain why it...
  47. S

    Can Two Control Signals Be Safely Connected to a Single Phase Contactor Coil?

    If I have a contactor that I want to use with two separate control sources, on a site with a single phase power source, is it possible to connect two 120V control signals to the contactor coil, potentially live at the same time and connected to the same source, without causing a short, or...
  48. A

    A coil of 25 turns of wire is suspended by a thread

    Homework Statement A coil of 25 turns of wire is suspended by a thread. When a current flows through the coil, the tension in the thread is reduced by 4.0 ´10-2N. http://members.shaw.ca/barry-barclay/Self-Tests/test11/Magnet20.gif Homework Equations F=IBL B=nμI[/B]The Attempt at a Solution...
  49. EMRF

    Field outside a ferrite cored coil

    The field outside a coil is given by I notice permeability of vacuum in the expression, and this makes sense since we are evaluating the field in space. Is there any effect to the coil having a ferrite core? Looks like there should not be (again the field is evaluated in space). However...
  50. Alettix

    Formula for torque on a coil in a magnetic field

    Hi! I have some simple questions on the formula for torque on a coil in a magnetic field, ie this one: τ = NIA sinθ where I is the current flowing through the coil, A is the area of one loop, N is the number of loops, B is the magnitude of the magnetic field and θ is the angle between the...
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