Coil Definition and 905 Threads

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. G

    Building a coil for generating ELF magnetic fields

    I am interested in replicating Bob Beck's work in the attached PDF document, dating back to 1978. After building a variety of coils Beck was able to demonstrate EEG entrainment with a 9-foot coil and by broadcasting an amplified Schumann Resonance frequency. The idea would be to interface said...
  2. C

    Find the resistance of the coil

    Homework Statement A water heater consisting of a metal coil that is connected across the terminals of a 24-V power supply is able to heat 270 mL of water from room temperature (20°C) to boiling point in 70 s. What is the resistance of the coil? (When entering units, use ohm for Ω.)...
  3. H

    Core material selection to achieve desired inductance of a coil?

    Hello everyone, I am trying to make a coil with the exact specs as the original. I have all the info I need except the actual core material used. I have all the measurements of the core and coil including: Wire gauge, # of turns and turns per layer,Bobbin dimensions, inductance without the...
  4. F

    Difference between Oudin coil and Tesla coil

    So, how do Oudin coils differ from Tesla coils, and how do they operate? All I have been able to determine is that the primary coil as well as the secondary coil is grounded, and that the primary and secondary seem to be one and the same, although I'm not even sure about that. Every website I...
  5. H

    Can I Design a Transformer Coil with These Specifications?

    I am in need of a transformer which has the following characteristics: Operating frequency 20kHz Turns Ratio 1:8 Primary 12V square wave @ around 100mA max Dual secondary coils (wound together with equal turns) (Note: Only 1 secondary coil will operate at any given time) Secondary 96V...
  6. J

    How to add capacitance in between two points end points of spiral coil?

    Hi All, I am at present working on coil design for RFID tag, i want to know how you add capacitance in spiral coil i.e. how you join two ends in spiral structure with capacitance in between, i have already calculated capacitance value needed to resonant at particular frequency. Any help is...
  7. R

    Calculating Conservation of Energy for Magnet Dropping Through Coil

    Hi I am trying to understand the effect of dropping a magnet through a single coil of wire. If there is one turn of wire, connected to a resistor, and a magnet with known mass and flux density is dropped vertically through the coil, a current will be induced in the coil. The forces acting...
  8. Drakkith

    Current in an Electromagnetic Coil

    What keeps the current in an electromagnetic coil from moving between the touching conductors and instead go through the conductor? Is it the resistance being much higher between two touching sections of the coil? Is there a small amount of current "leaking" between each loop where they touch?
  9. M

    Finding Specific Heat of oil with an electric heating coil

    Homework Statement To determine the Specific heat of an oil , an electrical heating coil is placed in a calorimeter with 380g of the oil at 10C. The coil consumes energy(and gives off heat) at the rate of 84W. After 3min the oil temperature is 40C. If the water equivalent of the calorimeter...
  10. L

    Rotating magnet inside coil = flux change?

    Apparently, that's how a lot of car speedometers work... but I don't understand how a rotating magnet inside a coil (or any conductive material, really) can induce a current in the coil. I can understand how pushing a magnet in and out through a coil can induce current, because Flux = Area...
  11. P

    Engineering Solving Series Circuit with 10Ω Resistor, Coil and Capacitor

    Homework Statement A series circuit consisting of a 10 ohm resistor, a coil and an ideal capacitor is connected across a 200 V, 60 Hz power supply. The current drawn is 8 A. The voltage across the coil is 120 V and its power factor is 0.8 lagging. Determine (a) the voltage across the...
  12. S

    Coil Winding: How to Layer Coil Turns

    Hello everyone I have a quick question on how to wind overlapping layers of magnet wire around a coil form. How do you layer coil turns for a coil? Do you just start at the top of the coil form and then coil over the top of the previous coil in the same direction and then just twist the two...
  13. P

    Torque on a coil in a magnetic field

    Homework Statement A cylinder with mass m = 262 g and length L = 12.7 cm has a wire longitudinally rolled up around it, such that the rolling plane, with N = 13 turns, contains the axis of the cylinder and is parallel to a plane which has an inclination θ with the horizontal. The cylinder is on...
  14. S

    Magnetic bullet fired through a coil can fire another bullet?

    Magnetic bullet fired through a coil can fire another bullet (no amplifiers, batteries, etc. are involved) A magnetic bullet, fired through the middle of a coil, can induce enough current that a nichrome wire connected to the ends of the winding gets hot red and is able to ignite a charge of...
  15. B

    Magnetic flux through a coil. Field generated by a straight conductor.

    Hi! I'm stuck on a problem concerning the magnetic field produced by a long straight conductor: A triangular piece of conductor (N=1) rests in the vicinity of a long straight conductor with a current I=50A. What is the magnetic flux through the triangle if a=1cm? (See attached file). My...
  16. M

    Induced EMF through a coil How/Why?

    Homework Statement In a lab I passed a magnet through a coil and measured the voltage. I need/want to know why when moving a magnet through a coil you induce a current. I don't necessarily need a direct answer - I more just want to know if my argument holds and where to look if I'm...
  17. Telemachus

    Magnetic induction for a tesla flat spiral coil

    Hi there. I have a current I running throught a tesla spiral coil, and I have to compute the magnetic field at the center of it. The tesla coil has N turns, and an inner radius a, and outer radius b. This is the tesla spiral coil: The courrent enters through the outer cable, and goes out...
  18. S

    Valve spring in engine, why the closer coil must be down?

    In engine, there is valve and the valve spring. If you have ever look at the valve spring before, then you will notice that one end has its coil closer together than the other end. So a valve spring is a kind of progressive spring. In almost all engine repair manual I read, the instruction is...
  19. R

    Solving Equilibrium of Glass Cylinder w/ Coil Wrapped Around It

    Homework Statement A glass cylinder of radius R, length l, and density \rho has a 10-turn coil of wire wrapped lengthwise, as seen in the figure . The cylinder is placed on a ramp tilted at angle \theta with the edge of the coil parallel to the ramp. A uniform magnetic field of strength B...
  20. K

    Building a Tesla Coil: What You Need to Know

    I'm getting ready for my Christmas break project and I've settled on building a Tesla coil. I was looking at this << link deleted by Moderators >> but I'm still not really certain about what the components do and why they're needed. I kind of understand what a capacitor and transformer is but...
  21. O

    How do you power an ignition coil

    Hello, I've just bought a HV Spark Coil from this site: http://www.rmcybernetics.com/shop/high-voltage/hv-spark-coil/prod_4.html And I was wondering if anyone could help me on how I could power it? I'm really poor on money at the moment since I've just spent it on this item, so if anyone...
  22. M

    How to Design a Coil to Achieve 0.5 Tesla?

    hello everybody i'm a student to mechanical engineering and I'm in my last year of my studies. in this year i supose to make a project and in part of my project i need to know how to design a coil that will gives me 0.5 tesla inside the core of the coil. unfortunatly, after a lot of searches...
  23. S

    Exploring the Effects of Self-Inductance and DC Excitation on Coils

    Hi, When coil is excited with ac because of varying nature of current ,flux of varying nature will be developed in coil and because of varying flux emf will induce in coil. what will happen if coil is excited with dc? intially cureent will increase from zero to maximum and is...
  24. R

    Magnet & Coil: Causes of Pistons Stroke

    I have a situation that a magnet is placed near to a coil. Especially in pumps and the pump is working based on the stroke mechanisam. The coil is powerd up by a DC source of 12volts and the piston(which having magnet on it) is attracted by this coil called as stroke. The distance between the...
  25. E

    Behaviour of a piece of metal inside a coil

    Hello, I was thinking about this and I'm still not sure. I have a long coil (which has uniform magnetic field inside) and a piece of ferromagnetic. Coil is connected to some power source and is positioned perpendicular to surface of the Earth. If I put that piece of ferromagnetic metal...
  26. D

    Electric generator coil design

    Hi, i am developing a home-made generator but i am having some trouble with coil design. Going on Faraday's induction formula : V = N A (2 pi RPM/60) B a 50 turn coil with a radius of 20mm going at 20,000 RPM should give me 80 volts or so, in practice i am getting much less than...
  27. T

    How do I fix the primary part for my 1.8KW Tesla tower?

    Hi everyone i am building a 1.8KW tesla tower and i have a problem i couldn't make the primery part round because the wire was too strong, does that effect my design and will it work ? [PLAIN]http://im13.gulfup.com/2011-11-01/1320190449301.jpg
  28. R

    Newby Question on Inductive Sensor Coil Specs

    I'm an old digital guy working on a little analog oscillator project so I'm a bit in over my head. The objective is to detect alloy deviations in samples of aluminum scrap: a very simple go/no-go detector I've cobbled together an inductive meter design using a dual op-amp sine wave...
  29. S

    Mutual Induction of a solenoid and a coil

    Homework Statement A single-turn circular loop of radius R = 0.235 m is coaxial with a long 1780 turn solenoid of radius 0.0435 m and length 0.850 m, as seen in the figure below. The variable resistor is changed so that the solenoid current decreases linearly from 6.12 A to 1.46 A in 0.230...
  30. S

    Mutual Induction of a solenoid and a coil

    Homework Statement A single-turn circular loop of radius R = 0.235 m is coaxial with a long 1780 turn solenoid of radius 0.0435 m and length 0.850 m, as seen in the figure below. The variable resistor is changed so that the solenoid current decreases linearly from 6.12 A to 1.46 A in 0.230...
  31. Y

    Equivalent circuit of induced EMF of coil.

    I want to model a coil circuit with induced EMF. I want to verify that my model is correct in a circuit. That the voltage developed across the load is calculated correctly. From the equivalent circuit, you can see the current depend on the jX_L and it acts as a low pass filter in the complete...
  32. M

    How does the magnetic field strength decay(radially) inside a solenoid coil?

    I'm looking at redesigning a hydraulic solenoid valve with the aim of reducing the package size. The solenoid coil is by far the largest component of the device, with about 4000 coils arrayed in about 90 layers stacked on top of each other. I'm wondering if I can reduce the size by removing some...
  33. W

    Induction coil powering a crt: how does it work?

    A professor the other day used an induction coil power a crt tube like the one at the link below. http://chemteacher.chemeddl.org/services/chemteacher/index.php?option=com_content&view=article&id=99 I understand the general idea of both induction coils and crts, but what confuses me is...
  34. M

    How Do I Build a Coil Gun Without Exceeding SCR Limits?

    ...and need some help with a bit of engineering. I've got 5 2200μF capacitors @ 400V (I'm familiar with high voltage + current, just not inductors, and have the appropriate safety gear) in parallel with about .05Ω ESR a piece. These are running into a GE C150 SCR, which can surge up to 1200...
  35. D

    If we know the inductance of an iron-cored coil to be 200mH, and we

    If we know the inductance of an iron-cored coil to be 200mH, and we remove the iron core such that the core is now air, how exactly can we determine what the new inductance is with just this information? I played around with the equation for inductance, however, I could not seem to get it...
  36. M

    Will an induction cooker work in reverse if a hot pan is place on the coil?

    I was wondering whether an induction hob cooker would work in reverse if a hot pan is placed on the coil - so would this generate a current? I would assume not as the heat induction pan wouldn't be able to create a magnetic field in the coil?
  37. C

    Estimate induced emf in the coil

    [Solved] Estimate induced emf in the coil Homework Statement Consider a single-loop coil whose magnetic flux is given by this image: Estimate the induced emf in the coil at times near t = 0.3s, t = 0.4s and t = 0.5s This is for algebra-based physics. Homework Equations emf = -N*(change in...
  38. 0

    How to find the spec for a bend in a coil

    Howdy folks, I'm having trouble finding a spec for bends in wound wire i.e. a coil. For example if you take the coil, say 150mm long and roll it on a flat surface and it deflects from the table in places (wiggles), how does one possibly determine what is an acceptable bend and what isn't? It...
  39. B

    Suggested waveform Amplifier for electromagnetoc coil testing?

    Hi everyone, I am currently doing some experimentation with electromagnetic coils, I realize I will need a waveform amplifier for the testing using my rsr32 function generator. Could someone point me in the direction of a decently priced one?
  40. L

    Voice coil motor force control using slow decay mode

    Hi, I am trying to control a voice coil motor's force, which is directly proportional to the current through its coil. The direction of the force needs to be reversed, so I thought an H-bridge would be a good way to do it. I have read a lot about H-bridges but I am still confused about a few...
  41. L

    Multiplying equations - spiral coil heat transfer

    "multiplying equations" - spiral coil heat transfer Hi, I was wondering if anyone could explain to me what is meant in this article by "Multiplying equations 8 & 9". I have both equation 8 and equation 9 however I cannot seem to work out how to get equation 10...not sure if it's something...
  42. M

    Does the direction of winding affect the induced emf in a an inductor coil?

    Hi, What if the inductor coil is wound one way rather than the other. Then the circular flow of current will be clockwise in one case and anticlockwise in the other. And if the inductor is connected to an ac source, then the current will vary. Now in both the orientations, the variation...
  43. S

    DURKOOOL DM84-2012-35-5024 Power Relay: Contact DC Voltage & Coil Activation

    considering this relay http://my.element14.com/durakool/dm84-2012-35-5024/power-relay-dpdt-2co-24vac-8a-pc/dp/1557207" what does contact DC voltage meant? and to energize / activate the coil i need a 24v current to do the job?
  44. Y

    Finding Magnitude & Direction of Force & Torque Exerted by B on Coil

    Homework Statement A coil of wire consisting of 40 rectangular loops, with width 16 cm and height 30 cm, is placed in a constant magnetic field given by B = 0.055Tx + 0.210T.z The coil is hinged to a fixed thin rod along the y-axis (along segment da in the figure) and is originally located in...
  45. E

    Emf / coil induction from a spark

    Homework Statement suppose we have a coil sitting on a desk (with radius =1), and then a spark passes by the side of it, in such a way that the magnetic flux through the coil is maximized. The coil is attached to a full wave rectifier which is connected to a very large capacitor. There is an...
  46. F

    Induced Emf: Magnet Passes through a Coil

    I'm doing a lab write-up for physics 2. The experiment is about the title, a bar magnet being dropped through a solenoid. I have to explain four graphs that plot the change in emf (y axis) vs. time (x) axis. There are incoming and outgoing peaks on these graphs. I have to tie these results...
  47. davenn

    Induced voltage with coil between 2 magnets

    hi gang, Just building a seismometer I have 2 x 2.5cm disc rare Earth magnets spaced far enough apart for a coil of wire to move between them. Would you expect there to be any difference in induced voltage into a coil between 2 magnets when the magnets are orientated to attract or repel ...
  48. A

    Force of neodymium magnet inside an electromagnetic coil

    Hey guys, Im trying to design a electric gear shiftier for a motor bike. Basically I require about 200N of force to change gear with a 10mm throw (in both directions). I would like to use a tube neodymium magnet. (23mm diameter 25mm high with a 5mm hole throw the centre with a N48 grade) What I...
  49. A

    Force of neodymium magnet inside a electromagnetic coil

    Hey guys, Im trying to design a electric gear shiftier for a motor bike. Basically I require about 200N of force to change gear with a 10mm throw (in both directions). I would like to use a tube neodymium magnet. (23mm diameter 25mm high with a 5mm hole throw the centre with a N48 grade) What...
  50. H

    What materials are best for building a Helmholtz coil?

    Hello PFs, I need to build some Helmholtz coils, and I was wondering if anybody here had suggestions on what to make the actual rims that hold the wire in a coil are generally made out of? So far its been suggested that I use bicycle rims, but even that creates a question--aluminum or steel...
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