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. E

    Is it possible to make a coil burner portable?

    I am trying to develop a product that would use a portable heating element. For example: If I wanted to use a coil burner, is there a way I could make it cordless using let's say a rechargeable battery? It does not necessarily have to be a coil burner. It just has to been something that...
  2. C

    North Pole Entering a coil wound counterclockwise

    Electricity and Magnetism (Polarity) Homework Statement Draw and indicate the current flow for the following situtions a) A north pole entering a coil wound counterclockwise b) A north pole exiting a coil wound counterclockwise Also is you could please explain coils, and...
  3. S

    What is this coil inside this AC to DC power converter?

    I have been studying the plans for a few AC to DC converters and I understand that the basic conceptual design is one where the AC power is transformed to lower the voltage and is then passed through a bridge rectifier to convert that power to what I call hopping DC. The power is then smoothed...
  4. J

    Which Coil Shape is Better for Eddy Current Measurements?

    Hi, I'm currently in a dead spot of my mini-project where I've to decide upon the coil shape. I can't find adequate definition of both coils by the means of: - size - losses - frequency range - inductance - skin depth which makes it impossible to argue which one would be better...
  5. S

    Can't have high voltage function generator. What about low voltage Tesla coil?

    According to many knowledgeable people on the internet, an affordable "high" voltage function generator does not exist. I would have liked to have had electrodes operating at >50v with frequencies up to 15 Mhz but it seems such a function generator is out of my reach. So I want to know if a...
  6. B

    Perpetual Battery with Pickup Coil and Magnents

    Hello, I recently was thinking about an idea for a perpetual battery. I have an extremely limited amount of Physics knowledge (just a Conceptual Physics [Algebraic Physics] class) as I am still in high school. Does anyone know if this would work: 1. Have a tube 2. Wrap the tube in copper...
  7. S

    Calculating Resistance and Inductance of Coil in AC Circuit

    1. Homework Statement . A wire coil has both resistance and inductance, and is connected in series to an AC power supply with 80Hz and 180V, drawing 0.4A current and 18W power. The circuit consists of a single loop. 1. Calculate the inductance and resistance of coil 2. Plot vector of...
  8. G

    Induction Coil Failure with increaseing inductance as coil is unwound

    I have a 13 layer 130mH induction coil that failed and now registers 6.64mH. During the failure analysis the coil was unwound layer by layer and the induction dropped in steps of 0.7-1.5mH to a value of 1.3mH until the 8th layer was removed the the inductance increased to 5.4mH. Then the 9th...
  9. R

    Nature of Coil and magnet fields?

    I find it difficult to visualise how the magnetic field generated by a coil can be the same as the field of a permanent magnet. Are the magnetic fields the same or is it just that the effects are the same in that they both attract iron or magnets in the same fashion? Visualising the field...
  10. Artlav

    Tesla coil with voltage doubler?

    I want to power a small-ish tesla coil from a 8KV 500W transformer with a voltage doubler to raise that to 16KV. Problem is - it works considerably worse (shorter sparks, LOUD gap) than with a 30KV 100W flyback, spark gap being the same, set at about 12KV. One issue appears to be that...
  11. I

    Faraday's Law (Flux on one coil due to current through another Coil)

    Homework Statement There are a lot of numbers in this problem. Just about the only way to get it right is to work out each step symbolically first,and then plug numbers into the final symbolic result. Two coils of wire are aligned with their axes along the z-axis,as shown in the...
  12. Z

    Heat transfer for a oven coil.

    I'm curious how heat transfers between the heating element in my electric oven and the air in the oven. Say when I first turn on my oven the air is at room temperature (say 70F) and the surface temperature of the heating coil is at say 500F. After some time passes, the air in the oven rises...
  13. J

    How to find inductance of a coil with two concentric ferromagnetic cores?

    Homework Statement This isn't exactly a homework question so there aren't any data/numbers to work with. I just want to know what to do if there are two ferromagnetic cores inside a coil of wire, arranged as concentric cylinders. Or how to account for the air gap between the core and the coil...
  14. T

    Effects of doubled over Tesla Coil

    This is something that just occurred to me. I was cleaning out an old closet when I came across some speaker wire, kind of like this. I was wondering, what would happen if I wrapped that around a tesla coil secondary coil? You have two separate coils interwinding, essentially, so would the...
  15. F

    What Causes Inverted Voltage Peaks in a Rogowski Coil?

    I've been doing some test on a rogowski coil that I built. It is like an air-cored current transformer. I am using it to measure high frequency pulses. The picture shows a discharging capacitor being captured by a current probe (above) and by the rogowski coil (below). I don't know what is...
  16. J

    Finding the phase between coil and its magnetic field

    Hey Guys, I am just trying to wrap my head around the results I've gotten and was wondering if anyone can check my work. I was basically trying to calculate the magnetic field along the z-axis of a infinitely long coil. Here are some questions and concerns: 1. Did I calculate the Bfield...
  17. S

    Heating coil wire resistance and length of wire required

    Homework Statement A portion of Nichrome wire of radius 2.50 mm is to be used in winding a heating coil. If the coil must draw a current of 9.25 A when a voltage of 120 V is applied across its ends, find (a) the required resistance of the coil and (b) the length of wire you must use to...
  18. E

    Inductance of a coil (negative inductance?)

    Hi everyone, I encountered a problem as a part of the solution of which I needed to get the i-V relation across a solenoid to gain some intution in the other parts of the problem, which is the well known expression VL=LdiL/dt, where V and i are referenced with respect to the passive sign...
  19. D

    How Do You Calculate Induced Voltage in a Coil with External Magnetic Field?

    Hello. Say I have a single turn of a coil in an external magnetic field. How do I calculate the voltage induced in this turn ? Initially I would use Faraday's law ∇×E = -j ω B But what should I use for B ? Will B not be a combination of both the external field as well as the field...
  20. L

    Building a speaker, have a few questions about the voice coil and magnets

    Hi there, I'm building a speaker for my intro to EE class. We were given ten small washer magnets, some washers, a nut and a bolt. Enameled wire is also provided. My group prototyped a speaker with the following configuration: Voice coil wrapped around a paper tube which fits around the bolt...
  21. S

    How many turns do I need for a compact air-core coil with specific dimensions?

    Hello there Its a air core coil I am not too sure how to calculate the number of turns I have to wind. Specs are below Height : 4mm Outside D: 9.5mm Inside D :7mm Coil wire thickness : 40 AWG / 0.08mm Coil resistance : 55 Ohms Coil weight : 0.7g Important figures highlighted. I...
  22. M

    Why Is My 15kV Tesla Coil Not Working?

    Hi I've built a NST 15kV tesla coil and I hooked it up today and it kinda didn't work. I'm wondering if anyone would like to help me as it's a school project and needs to be finished ASAP so if anyone might have any ideas / advice, that would be amazing! Pictures of all my parts...
  23. M

    What is the Electromotive Force Induced in a Moving Coil in a B-field?

    Homework Statement A 25-turn coil has a radius of 1 cm and it is carrying a current of 1 A. The coil is in a constant B-field of 1 T (directed along the coil's axis). The coil is moving perpendicularly to the B-field at a speed of 1 m/s. a) Is there an Electromotive force induced in the...
  24. M

    Max EMF in a Model AC Generator Coil

    Homework Statement In a model ac generator, a 500 turn rectangular coil, 8.0 cm by 20 cm, rotates at 120 rev/min in a uniform magnetic field of 0.60 T. (a) What is the maximum emf induced in the coil? (b) What is the instantaneous value of the emf in the coil at t = (∏/32)s? Assume that...
  25. D

    Torque on a current carrying coil with an applied frictional force?

    Homework Statement There's a diagram in my book but imagine a coil in a square shape attached to a vertical shaft, the diagram for convenience sake represents the coil as one circular wire exactly like a wire actually looks. However, the coil has 410 turns and has an area per turn of 3.1 X...
  26. S

    Type of induced/back emf in dc motor's armature coil

    Actually this not a question, I want to justify whether my concept is right or wrong. So let's start. Faraday's law of electromagnetic induction e=Nd\varphi/dt explains the way of electromagnetic energy conversions. The induced voltage is always ac because the rate of change of flux is...
  27. N

    Computing the emf induced in a coil

    Homework Statement The following is Problem 1-13 on page 23 from Electrical Engineering Fundamentals, 2nd ed., by Vincent del Toro: "In the configuration shown in Fig. P1-13 the coil has 100 turns and is attached to the rotating member which revolves at 25 \frac{rev}{s}. The magnetic...
  28. H

    Different magnets with a coil, what are the currents?

    Hi. Can someone please explain/tell me what would be the resulting currents trough the coil in every of the three depicted scenarios in the attached picture, I'm confused here. Would the first and the second drawing produce the same result? Is there any current flow in the third drawing. Thanks.
  29. D

    Voice Coil Selection: Metal Bellow Pressure System

    I hope this post finds everyone well! I am currently trying to build up a system capable of providing pulsatile pressure (a sinusodial profile) to a silicone tube. In brief, the system consists of a linear voice coil actuator connected to a metal bellow. At the moment, I have worked out...
  30. G

    Calculating Force and Torque on Electric Motor Coil

    Homework Statement An electric motor has a square coil with 20 turns and an area of 150cm^2. the coil is free to rorate in uniform magnetic field of 300mT. If there is a DC current of 5.00A, passing through the coil: what is the maximum force on one side of the coil? and what is the maximum...
  31. T

    Energy stored in coil with given relationship between current and flux

    Homework Statement The relationship between the current in an N-turn coil and the flux created by it is given as: \Phi = \frac{ai}{b+ci} Determine the energy stored in the coil when the current varies from 0 to I. Homework Equations W = N \int{i d\Phi} The Attempt at a...
  32. leviterande

    Does this strange coil really consume 1700Amps?

    Hi, I have seen a couple of videos on youtube where people simply hook a homemade simple coil of copper wire directly to the House 120v AC. One of them for example hooked a close wound aircore coil with 14 gage wire(01.6mm), 6"(152mm)diameter, about 1" length and 30 turns only.. and...
  33. T

    Coil design and magnet orientation in a unique generator

    First, I am not an electrical engineer - I am a hobbyist building a prototype linear-stlye generator based on an idea I had which, for various reasons, cannot be built with magnets that pass completely inside of coil(s) like most of the ones I have seen described for wave energy capture and...
  34. K

    Orientation of magnet relative to coil and it's effect on inductance

    Say I have a coil that is stationary and I have magnets that move past it in a fashion similar to the example in this video: . What is the optimum orientation of the magnet and coil to induce the most current? I know I will want to optimize the rate of change of magnetic flux through the coil as...
  35. A

    Linear movement detector using magnetic, wire coil and transistors

    Hello, I have cool idea for a device and one hardest part of it is to detect the movement of the object. I think I can use a wire coil, and a small magnet attached to the moving object. When the object passes the wire coil (up or down), there will be small voltage inside the wire coil. It...
  36. M

    Copper fins coil with out pipe

    I am looking for copper fins the same as would be on a heating pipe. the fins need to be like a coil or slinky. If you have ever used or know who makes them please let me know. I am working on an invention and this is one of the parts i need. 2 to 3" OD and 3/4 to 1" ID
  37. J

    Coil Moving through a Magnetic Field velocity

    Homework Statement At t=0, a rectangular coil of resistance R = 2 ohms and dimensions w = 3 cm and L = 8 cm enters a region of constant magnetic field B = 1.6 T directed into the screen as shown. The length of the region containing the magnetic field is LB = 15 cm. The coil is observed to...
  38. M

    Magnetic image of a coil over a conducting surface

    Homework Statement If the coil in the figure is touching to an ideally conducting (σ=∞) non-magnetic steel from the A4-A5 side, what would be the magnetic field in the gap. Assume A1=A2=A3=A4=A5. Homework Equations The Attempt at a Solution I have calculated that when the coil...
  39. P

    EMF induced in a rotating coil

    Hi, So, I am learning about induced emf. I am having a hard time grasping the idea that we are interested in the angle between the normal to the plane of the coil and the magnetic field. In the standard illustration I actually understand it, but the following question confuses me. We are...
  40. H

    Coil winding direction on opposite legs?

    I am winding a transformer. I want to get it done right the first time. The transformer has a square core with a coils on opposite legs. I want the polarity to be the same on each coil so how do I wind them? Should the start of the windings be at the top of each coil? Should the...
  41. S

    Formula for average current on a coil inside a solenoid

    Homework Statement A solenoid of length 20.0 cm is made of 5000 circular coils. It carries a steady current of 10.0 A. Near its center is places a very flat and small coil with a resistance of 2.50 Ω made of 100 circular loops, each with a radius of 3.00 mm. This small coil is oriented so that...
  42. T

    Tesla coil with 555 timer troubleshooting help

    I attempted to build a tesla coil with a 555 timer but seemed to have failed some where. Perhaps you could take a look and give me some hints on what to try in order to make it work. I attached some pictures as well. I made the secondary coil on a 1/2 (.875 OD) pvc pipe with a 10 to 1 ratio...
  43. C

    Coil Design for Uniform Magnetic Field?

    Dear Forum, I am attempting to make a treatment mattress or pad for PEMF treatment of osteoporosis. I have osteo, and there are commercial units available, but they cost ~$3K+! I have a capacitor discharge circuit, but need a coil design for the pad. I created a gauss probe with a linear hall...
  44. R

    Constructing a Tri-Axial Square Helmholz Coil

    Homework Statement I'm a summer REU student tasked with building a tri-axial square helmholtz coil setup. My frame will be made of aluminum while the wire used will be copper. I've been researching for days, having actually never studied these coils before, and I'm having serious trouble...
  45. B

    Wave Propagation in a Coil Spring

    I am studying the vibrations in a coil spring, and want to confirm with others that my derivation is correct. I found that for small oscillations the spring is described by the 1-D wave equation, with wave speed k*l^2/m. where k is the spring constant, l is the spring length, and m is the...
  46. P

    Rotational speed of a coil in a magnetic field

    This is for self-study. Homework Statement The armature of a motor has 97 turns each of area 190 cm² and rotates in a uniform magnetic field of 0.33 T. A potential difference of 24 V is applied. If no load is attached and friction is neglected, find the rotational speed at equilibrium...
  47. P

    Charge through a coil in a magnetic field

    Homework Statement At a certain place, the Earth's magnetic field has a magnitude B = 59 μT and is inclined downward at an angle of 70º to the horizontal. A flat horizontal circular coil of wire with a radius of 13 cm has 950 turns and a total resistance of 85 Ω. It is connected to a...
  48. N

    Anti-Helmholtz coil configuration

    Hi Say I have to coils in the anti-Helmholtz configuration as in the attached picture. It is pretty easy to find the field along the z-direction, as this is introduced in introductory EM. However say that I would like to know the field along the x-direction. This I don't know how to find...
  49. O

    Analyzing the Speed of a Permanent Magnet in a Coil

    If a permanent magnet rod enters a coil of wires at a certain speed will the permanent magnet slow down? I'm trying to build a generator of some sort. So i need to know is my logic sound. I'll give you scenario. Scenario: The permanent magnet slides into the coil at a speed of...
  50. P

    Using a DC source to generate a large magnetic field in a coil

    I am a mechanical engineer and I'm working on a project in which I need to generate a large magnetic field in a coil of wire. The current system uses AC power (480V or 230V) and I am exploring the possibility of using a DC battery source. The coil is has an OD of 72mm, an ID of 62mm and a...
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