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. W

    Faraday's Law and the radius of the coil

    I've only recently started learning basic electrodynamics, but I don't understand why a loop of coil with a small area and a magnet falling through will produce a larger peak to peak emf amplitude than a loop of coil with a larger area with the same magnetic field falling through. To clarify...
  2. Z

    Can I use capacitors to create a magnetic field with a transformer and coil?

    Hello. So I'm trying to work on a project with capacitors. I have a twelve volt battery hooked up to a transformer that produces 120 v ac. I would like to then hook the transformer up to five capacitors in parallel and then use the power stored i the capacitors to shoot through my coils to...
  3. S

    Mutual-Inductance of Rogowski Coil (Toroid of Circular Cross-section)

    Homework Statement Calculate Mutual-inductance of a circular cross section toroid. circular cross-section radius :a toroid mean radius :R Previous attempt for self inductance :https://www.physicsforums.com/showthread.php?t=537149 Homework Equations B=μNI/(2pi(R+y))...
  4. C

    Resonance frequency of heating coil

    I am doing R&D and have been hit by a problem. I want to find the resonnce frequency to my heating coil without having to hook it up to the rest of my oven. I fall into the problem because I don't have the stray funds to buy a frequency generator. I heard that with capacitors and an oscilloscope...
  5. M

    What is the mutual inductance between a coil and an infinite straight line?

    Homework Statement Find the mutual inductance between a coil with N loops and an infinite straight line with current I on its axis. Homework Equations M12 = M21 = flux 1/I 2 = flux 2/ I 1 emf = -d/dt flux i = emf /R R = eta*l/S The Attempt at a Solution I have done this...
  6. STEMucator

    Torque on a Coil: 20-Turn Rectangular Coil in Mag Field

    Homework Statement The attachment shows a rectangular ##20-turn## coil of wire, of dimensions ##10 cm## by ##5.0 cm##. It carries a current of ##0.10A## and is hinged along one long side. It is mounted in the x-y plane, at angle ##θ = 30°## to the direction of a uniform magnetic field of...
  7. M

    Calculating Induced Current in a Circular Coil with Time-Varying Magnetic Field

    Homework Statement A circular coil has N equal loops with diameter C. Each loop has resistivity η and diameter d. There is a field on the central axis of B(t) = B_0 sin(ωt). Find the induced current (ignoring other fields) Homework Equations emf = -d/dt * flux(t) i = emf/R R = η*l/AThe...
  8. E

    How can I calculate the force between finite coil and metal plate?

    Hi, I would like to calculate the force between a finite coil and a nearby metal plate. A pulsed current is supposed to flow into the magnetic coil, which will generate a magnetic field near the coil. Due to this magnetic field, an Eddy current will be produced in a nearby metal plate and...
  9. N

    How Does Increasing Current in Helmholtz Coils Affect Electron Motion Radius?

    Homework Statement If the acceleartingb voltage remains constant, but the current through the hemholtz cois is increased, what would be the effect on the radius of the circular motion of the electrons? Homework Equations The Attempt at a Solution
  10. I

    What is the Formula for Finding the Area of a Circular Coil?

    Homework Statement Please see attached image file I understand everything in this problem except I don't know how they got (1/4) in the area of a coil. Can someone explain this? I have googled it and I am not getting a clear answer. I thought the area of a coil could be (pi(r)^2)L...
  11. D

    Why won't a magnet slow down when falling through a copper coil?

    Please watch this video (link: http://www.youtube.com/watch?v=JN-A3RryOC8) for reference. As you can see, the magnet does not slow down (at least, not appreciably) when falling through the copper coiled around a PVC pipe, and I can't figure out why.
  12. J

    Magnetic Field Calculation for Spherically Shaped Coil

    Hello, I'm attempting to calculate the magnetic field \mathbf{B} outside of a coil with current density, \mathbf{J}, and whose volume is a section of a sphere. Here is a diagram of the cross-section of the coil: (The wire ridges are aesthetic and aren't considered in the calculations - I'm...
  13. D

    Magnitude of EMF when the armature coil is in different positions?

    I am currently studying for a Magnetism and Electricity exam coming up. I was just wondering, within the topic of Electromagnetic induction; my textbook states that if an armature coil of some sort -either from an AC or DC generator was placed horizontally into a magnetic field that is also...
  14. P

    Coil placed in a time-varying magnetic field

    Homework Statement A coil 3.75cm radius, containing 500 turns, is placed in a uniform magnetic field that varies with time according to B = (1.20 x 10-2 T/s)t + (2.70 x 10-5x4)t4. The coil is connected to a 610-Ω resistor, and its plane is perpendicular to the magnetic field. You can ignore the...
  15. R

    Double resonant solid state tesla coil

    So, the igbt bridge system i have going is a 600 volt 300 amp full bridge of cm300 igbt's and i was wondering if a .660uf tank capacitor is too big for my system. The mmc is made out of 2000 volt 1uf capacitors, 2 strings of 3 in series. Thank you.
  16. D

    Why Does Torque Change in a Rotating Coil Even if the Force Remains Constant?

    Homework Statement for this question, since area of cutting of magnetic field change, so magnetic flux change, f is unchanged . but i don't understand why the torque will change since the force is unchanged, since torque=FORCE X DISTANCE FROM THE ROTATING PIVOT Homework Equations...
  17. W

    Laminated iron core inside a coil magnetic field question

    A laminated iron core was inserted into a coil with an AC current flowing in the coil. 1.The current in the circuit decreased after inserting the core. 2.Also the magnetic field was found to be stronger on the outer edge than in the center of the laminated iron core. How to explain the fall...
  18. D

    How fast Coil Springs are? Greatest mystery today?

    Hello, Hope someone finds this a challenge. Thought it would be a snap to find out, goggled it, nothing. Weeks later have not found one person in the world that knows of one example of how fast coil springs release. Just talked with Hyperco a major manufacturers head engineer, he...
  19. Y

    How Does Water Affect the Inductance of a Coil?

    water as coil "core" How much a coil inductance of 0.1 mH (3 cm long, some 50 turns wound around 5 cm diameter empty plastic pipe) may change when water enters the pipe ?
  20. I

    Magnetic Field Strength versus Coil Density

    Homework Statement We did a lab where we measured the magnetic field strength of a wire coil versus the coil density of the wire coil, keeping current constant. We determined the relationship of B (magnetic field strength) versus n (coil density) to be direct. I need to explain why this is...
  21. U

    Inserting iron core in an inductor coil

    Homework Statement A coil is connected in series with a bulb and this combination is connected to a DC source. When an iron core is inserted in the coil, what will happen to the brightness of the bulb? The Attempt at a Solution When the iron core is inserted, the magnetic field...
  22. A

    Mutual Inductance Between a Coil and a Solenoid

    Homework Statement A small, thin coil with N2 loops, each of area A2, is placed inside a long solenoid, near its center. The solenoid has N1 loops in its length L and has area A1. Find the mutual inductance as a function of θ, the angle between the plane of the small coil and the axis of the...
  23. P

    Coil Gun: How It Works & Physics Behind It

    What is the physics behind coil gun. For the magnetic field part, that is convert a electric voltage to the magnetic field. How the magnetic field related to the voltage? Is there any equation for the conversion the voltage to the magnetic field, maxwell or others? After that, the...
  24. G

    Mutual Inductance of RC Circuit on a Small Coil

    Homework Statement My textbook has two problems, based on the same premises, but the solutions manual solves each of them differently, so I was wondering why? Here are the two problems... 1. In the circuit shown in Fig. P29.49, the capacitor has capacitance C = 20μF and is initially charged...
  25. patrickmoloney

    How Does Coil Rotation Affect Magnetic Flux and EMF Generation?

    Homework Statement A planar 50-turn coil of area ## 0.20m^2 ## is rotated in a uniform ## 0.15 ## Tesla magnetic field by a motor at a constant angular velocity ## \omega = 315 s^-1 ## The axis of rotation is in the plane of the coil and is perpendicular to the magnetic field. At time ## t =...
  26. F

    Coil & Generator Homework: Solve for Current & Reactance

    Homework Statement problem is attachedHomework Equations formula sheet is attachedThe Attempt at a Solution 1. I=v/z=110v/11Ω=10A 2. sinø=(Imax)(X)/v=(10A)(9Ω)/110V ø=54.9° 3. I don't know what to do for this. I want to use Xc=1/ωC and solve for C but I need to first find Xc somehow
  27. L

    Induced current in a coil around a solenoid

    Homework Statement A coil with 150 turns, a radius of 5.0 cm, and a resistance of 12 Ω surrounds a solenoid with 300 turns/cm and a radius of 4.3cm; see the figure. The current in the solenoid changes at a constant rate from 0 to 1.8 A in 0.12 s. Homework Equations B from solenoid =...
  28. P

    How to simulate a coil in Ansoft Maxwell 3d?

    Hello, I want to simulate a coil of a transformer in Maxwell (3D), but my problem is: the coil design is not a closed path. Imagine that you draw a ring and then you cut part of it. You get something like a "letter C". In these two terminals I`m going to put an excitation (100A, for...
  29. T

    Calculate Average Emf in Rectangular Coil

    Homework Statement A rectangular coil of wire has 65.0 turns and is 30.0cm by 43.0cm . Initially the plane of the coil is perpendicular to a uniform external magnetic field. It is then rotated till its plane is at an angle of 35.0∘ with that field. The magntude of the external field is 1.90T...
  30. H

    Improve Your Transformer Design Process with Affordable Coil Design Software

    Hi everyone, I have been designing wideband transformers for a while. My biggest problem is the time it takes. So, I am looking for good software for coil design. I need something that can calculate from inputs the inductance, total number of turns, number of turns per layer, resistance...
  31. J

    Tesla Coil Thruster: Could it be Possible?

    This may well be a very silly bordering on sci-fi question, but I was just thinking about this. Tesla coils can shoot off some truly huge bolts of lightning. My understanding is that this is due to the charge in the secondary coil being "shaken" back and forth like water being sloshed around...
  32. V

    What Is the Magnetic Vector Potential of a Finite Length Coil?

    Hi Basically I want to examine the effect of a magnetic vector potential created by a coil on the spin of an electron in a Coulomb potential. The Hamiltonian of a charged particle in a Vector Potential is well known. But I have a problem in calculating the Magnetic Vector Potential of a...
  33. E

    How does the direction of a coil antenna affect its directivity?

    Hello, I am afraid this might be a simple question but I am really confused. I am currently working with ferrite core coil antennas, and I am having trouble at understanding their directivity. The cylindrical ferrite core is placed in the middle of the loops. What I have read is that...
  34. X

    Power generated from magnet and coil

    Hey guys, I'm an engineering student and for my project i am planning to use a power generator based on magnet and coil like those hand power shake flashlights. I am using gauge 45 AWG copper wires (0.051816mm) and coiled to have 200 coils. The coil size will be 2.5cm. The magnet i am using...
  35. R

    Ideal coil size for a low wind turbine.

    I can't find anything I can make heads or tails out of so if you guys can help I thank you. I would like to design a wind turbine and be able to get as much power as I can out of each of it's coils. If I start with a magnet that is 1.1811" in Diameter and it is .125" thick with a grade of N52...
  36. N

    What is the Lagrangian and equation of motion for a bead on a rotating coil?

    Homework Statement A bead of mass m is threaded around a smooth spiral wire and slides downwards without friction due to gravity. The z-axis points upwards vertically. Suppose the spiral wire is rotated about the z-axis with a fixed angular velocity \Omega. Determine the Lagrangian and the...
  37. L

    Tesla Coil - Capacitor necessary?

    Hi to all, It may be a low-level question, but nevertheless, one to which I'm looking for an answer. The main question is as follows: - Within a Tesla coil, what is the main purpose of the capacitor and spark gap? Other such questions arising from the principle question: - What would...
  38. W

    Why Is My Coil Suppressor Circuit Allowing Voltages Above 130V?

    I am trying to make a coil suppressor to restrict any voltage above say 130v. It is a simple VDR RC circuit. I am using a resistance of 47ohm, 250v and a capacitor of .1nF 250v a VDR of 130v. But the circuit is not working as expected. Is it because of the voltage spec of resistance and...
  39. kira506

    Understanding Self-Inductance of a Coil: How Does it Happen?

    Self inductance of a coil : how does it happen ? I've got some hardtime trying to imagine how it happens , the phrase which confused the most while studying was "each turn acts as a small magnet ",so why does it change polarities at the moment of switching the circuit on or off ? Also the whole...
  40. Entanglement

    What is the relationship between magnetic flux and coil wire?

    Magnetic Flux= BA is A the surrounding area affected by the flux or the area of the coil itself that is affected by the flux
  41. M

    Ignition Coil and Capacitor oscillations

    BOB S had posted this in a now closed thread: https://www.physicsforums.com/showthread.php?t=360072 Regarding this analysis ... https://www.physicsforums.com/attachment.php?attachmentid=20126&d=1250393723 My questions ... Q1) Does this oscillation from the L-C circuit actually...
  42. E

    Understanding Flux Density in Coils: Equations and Factors Explained

    Hello, I am looking into magnetic flux density in coils can anyone tell me if there is a general equation that equates flux density to the electric current, the coil's dimensions and number of turns? Any help would be appreciated. Thanks.
  43. J

    What does it mean to 'drive' a coil?

    I hear this term a lot but couldn't find much from a google search My initial guess is that we put a AC current through a inductor coil to create a magnetic field. Am I close?
  44. B

    How to Calculate Induced EMF in a Rotating Coil?

    Homework Statement a coil starts perpendicular to a magnetic field of 0.365 tesla , it has a length of 0.15 cm and a height of 0.25 cm , it rotates with a frequency of 1800 rotation / min . it also has 30 turns calculate the mean induced Emf during quarter a rotation Homework Equations...
  45. S

    Optimizing Activation Coil Selection for Maximum Gamma Flux

    What is best way to figure out which of these activation coils would yield a higher gamma flux: 27Al, 58Ni, and 115In. I have a PuBe neutron source, which I am told to just use a 4.5MeV neutron-energy. I am running MCNP calculations to find flux at a point away from the foil. I knows the...
  46. P

    Multiple coil field math for magnetic train

    i need to know how to calculate the inductance and field strength of a coil while another coil directly beneath it is turning off and coils under that are also turning off i also need to know how quickly the coils will turn off and if i can accelerate the process if it makes a difference the...
  47. E

    Inductance for an arbitrary shape coil composed of single loops

    Dear all, I would like to estimate the inductance of a rather arbitrarily shaped coil composed of multiple single loops. For example, I am wondering about the inductance of sandglass like coil which has many turns at the edge and less in the middle. The inductance of a single loop seems to...
  48. M

    What is the maximum emf induced in a rotating coil with given parameters?

    Homework Statement A 104-turn coil rotates 7.14 times per second. The coil has a cross-sectional area of 0.670 m2 and the magnetic field through the coils is 0.0720 T. What is the maximum emf induced in the coil? Homework Equations Honestly the rotating coil is throwing me off. But I...
  49. A

    How Does a Toroidal Coil's Magnetic Field Change with an Air-Gap Insertion?

    Homework Statement A toroidal coil,with N turns of wire carrying a current I, is uniformly wound around a toroidal core that has a mean radius a, a cross-sectional area A= ∏(d/2)^2, and is made of a linear, isotropic homogeneous material with relative permeability μr. You may assume that the...
  50. V

    Archived Derivation of total magnetic field with changing distance in a coil?

    Homework Statement You are a member of a research team studying magnetotactic bacteria. Magnetotactic bacteria from the southern hemisphere preferentially swim to the south along magnetic field lines, while similar bacteria from the northern hemisphere preferentially swim to the north along...
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