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.

View More On Wikipedia.org
Recent contents Top users
  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. makkhi

    What is phased array head and neck coil in MRI?

    I was reading this article " The Effect of Head Rotation on the Geometry and Hemodynamics of Healthy Vertebral Arteries" They used an MRI machine with a phased array head-neckcoil and a phased array superficial coil. what are they?
  7. T

    Finding Induced EMF of secondary coil

    Homework Statement There's a primary and secondary coil. The primary coil has 15 turns, and the secondary coil has 16000 loops. The 25000 V is applied to the primary coil, what will be the induced emf in the secondary coil. Homework EquationsThe Attempt at a Solution Very confused as to how...
  8. V

    How Does Flow Rate Affect Heat Transfer in a Copper Coil?

    Hi, I am currently doing my final year project in college. I am using a copper pipe which is 8m long with 8.5mm ID and 10mm OD. The pipe is bent into a coil which will be placed inside a acrylic box. The aim is to pump water through the coil to get the box to a desired temperature. At the...
  9. H

    Coil vs Solenoid: Understanding the Difference and Equations for Magnetic Fields

    Homework Statement I'm having problems figuring out the difference between a coil and a solenoid. My book provides two equations for magnetic field, and they are similar, but one depends on the radius (coil) while the other depends on the length (solenoid). Homework Equations Bcoil = μNI/2a...
  10. A

    Help Needed: Building a Tesla Coil - No Arcs Coming Out Toroid

    Hello all, I am in the process of building a tesla coil and I need a little help. I have everything completed enough that I can start testing it. I plug the coil in and the spark gap fires immediately and continuously, but no arcs come out the toroid. I tried moving the toroid closer to the...
  11. S

    Number of turns in coil to get an output of 8V

    Hello! First of all excuse my English. I'm Swedish. I'm doing an exprement in which I utilize the energy from the rotation in a stroller wheel to charge a 5V battery . I plan to make a magnetic generator with a disc placed on a 10 " wheel, consisting of the 20 Neodymium magmeter on the radius...
  12. B

    Design a coil with a variable pitch but a constant length?

    I believe what I am attempting to do is not possible but here goes. I want to design a fixed overall length coil which I can manually adjust the pitch on. Optimally one would be able to grab the coil and by twisting it in place would be able to change it's pitch by changing its diameter but not...
  13. B

    Magnetic Field in plane 90 degrees off Helmholtz coil axis?

    In a recent Physics lab, I experimented with the magnetic field generated by two Helmholts coils. I used a Hall probe, and some software created by the Grad students to plot the field strength against probe position in a series of configurations. I understood almost all of the lab, I...
  14. milkman_78

    Can a Micro-Generator Fit These Size and Power Constraints?

    Based on what I have gathered so far, I don't see why a micro-scale generator wouldn't work, but then again I am a geographer with modest calculus skills. My biggest problem is not knowing how much I don't know, and I am hoping some kind and wise soul on PF can cure my ignorance. Let's say I...
  15. A

    Measuring a Coil of Wire With Ohmmeter and Balance

    Homework Statement A coil of fine copper wire has a resistance of 6.2 -Ω and a total mass is 14.4 g. What is the diameter d of the wire and what is its length L? (The density of copper is 8.96 g/cm3.) Hint Given: •Model the wire as a long cylinder of diameter d and length L. Write one...
  16. A

    Magnetic force on a charge outside of toroidal coil

    Homework Statement Turns of wire would around a toroidal core, carrying a sinusoidal alternating current i(t), represent a toroidal coil in my case. My question is, does magnetic force affect a non-moving charge outside of toroidal core and is there a magnetic field outside of toroidal core...
  17. R

    Finding forces/torques on a permanent magnet from a coil

    I want to know what methods there are for calculating forces by a current-carrying coil on a permanent magnet (the application I have in mind is electrical motors). I.e. given a geometry (like a CAD model of the magnet), the magnet type (e.g neodymium), and wire coil geometry, how are the forces...
  18. C

    Force on a magnet inside a short coil

    The equations are incredibly difficult, so I'm just after a general idea of how the force on a magnet bellow a coil changes with the distance to the coil. Shown bellow: Axial symmetry: o x o x cross section of coil o x o...
  19. N

    Why does my inductor coil have no effect on my circuit

    I have the circuit with a drawing below, to create sonoluminescence. One of the steps needed was an inductor coil in order to achieve electrical resonance within the circuit. The link provided here: http://www.macgeisler.de/nld/sbsl-howto.html told me to find the inductance needed through the...
  20. T

    How Can You Test a Coil for Shorts Without Disassembly?

    Let's say a radio power transformer or other electronic transformer (audio for example) has a short between two of its coils (for example, the enamel coating has burnt off). Is there any way to test it to find out without taking it apart? As I see it the short will be either between adjacent...
  21. P

    Wire coil in decreasing magnetic field

    Homework Statement A wire coil of 2 cm with 10 turns is in a magnetic field of 2 T. The field is perpendicular to the plane of each turn of the coil. The coil is wired in series with resistor of 5 Ω. The field drops at a constant rate to 0.0 T in 10 ms. What is the current through the resistor...
  22. V

    How is a flat coil polarized in comparison to a linear coil?

    I know that a linear voice coil is polarized from top to bottom, but how is a flat coil polarized? Would a flat coil be polarized from the inside to the outside? Where the inside(blue) is one pole and the outside(red) is the other? If you were to do multiple windings(stacked layers) would it...
  23. 8008jsmith

    Deriving Magnetic Field from Helmholtz Coil Lab Data | Homework Question

    Homework Statement I had a lab where we used Helmholtz coils to measure the period of a bar magnet (1/s2) vs output current. The graph of this is a straight line. Using the slope, I am supposed to be able to derive the C constant and then that divided by the intercept is supposed to yield the...
  24. C

    Do increased windings conflict with thicker coil diameter?

    I have read that to increase motor magnetism that an increase in the windings increases the number of tiny magnets that can be used to provide the magnetic force. I have also read that increasing the cross section of the rotor increases the efficiency. Finally I have read that increasing the...
  25. AdityaDev

    Calculating Heat Generated in a Coil due to Changing Current and Resistance

    Homework Statement What amount of heat will be generated in a coil of resistance R due to a charge q passing through it if the current in the coil decreases down to zero uniformly during a time interval ##\Delta t## Homework Equations ##dH=i^2Rdt## ##i=\frac{dq}{dt}## The Attempt at a...
  26. cseil

    Faraday's and Lenz's Law - square coil

    Homework Statement A square coil rotates around an axis passing through the center. It is inside a magnetic field of B= 0.6T uniform and constant. The side of the coil is a = 2cm, the resistance R is 0.1 ohm. The coil is powered by a generator that gives an emf = 0.2 + 0.24sin(ωt). The current...
  27. J

    Practical application; wire coil dripping.

    As part of a wire manufacturing process, heavy wire coils are being sprayed with oil to prevent corrosion. Final step is to have these coils dripped to eliminate oil excess. Basic question is; if I where to build a vibration platform/table to do this dripping, what would be a good consideration...
  28. D

    Understanding Coil Winding Direction & Polarity

    So I've been told that the direction that you wind a coil will determine the polarity of the induced voltage across the coil. I drew out two coils with clockwise and counterclockwise winding direction and with using the right hand rule and saying that the positive polarity of the induced...
  29. D

    Formula for Helmholtz Coil with a finite thickness?

    The formula for Helmholtz coil is given by mu*(0.8^1.5)*nI/R, where I is the current, n is te number of coil and R is the radius of the coil. Now assume the bunch of coils have a small 'thickness' w (so it looks like a hollow cylinder with a very small height), and the the two coils are...
  30. cseil

    Calculating magnetic force on circular coil carrying current

    Homework Statement A circular coil with center on the z axis and orthogonal to the xy axis carries a current. The coil is in a magnetic field B with axial symmetry compared to the x axis. B forms an angle θ with the z axis. Calculate the magnetic force acting on the coil. 2. Homework...
  31. J

    AC Coil Levitation - Get Expert Help for Science Fair Project

    Hi pf, I am trying to get a fun experiment for a science fair at school and would greatly appreciate some help. I have found the experiment I want to do in the video below (43mins 50seconds in). The school has a large aluminium plate so that is sorted. What I am having difficulty with is...
  32. L

    Thought experiment on magnetic field propagation

    Some 30 years ago I learned in the elementary school, that if I move a permanent magnet in a coil which ends are somehow electrically closed, than I need to apply force on the magnet, because the generated current creates a magnetic field which is against the magnet's field. However if the...
  33. P

    Electromagnetic Coil Strength from Moving Liquids?

    I was reading about drift velocity and according to http://amasci.com/miscon/speed.html 100VDC at 1A moving through ~12 AWG wire would produce an electron velocity of 8.4 cm/hr. Since that is incredibly slow I'm curious if a charged fluid (something like the oil used in an oil-based van de...
  34. Keystone

    Bending Light? – Questions & Answers

    Hi , so , i am not asking this question for invisibility or anything like that, but i do have a few questions. First off, i know that photons have no charge, but is there any way that electro magnetic pulses can effect their path when the copper coils that make the electro magnet are at very...
  35. M

    Why Does Rearranging an Inductor Yield Different Magnetic Fields?

    I found two ways to solve this problem, but I get two different solutions, it's confusing because I can't see the flaw in wrong solution. 1. Homework Statement Long cylindrical inductor of diameter D1 and inductance L1 is connected to battery and creates magnetic field B1. Inductor is then...
  36. BeautifulLight

    Dual voice coil speaker: Each coil get an inductor?

    1st order crossover desired low-pass frequency: 100hz At 8 ohms, that'd be about 12mH. But what happens with a DVC speaker? Each coil get a 12mH inductor? I'd like to think so... Speaker is 8+8 ohms and will be parallelled to a set of 8 ohm extended range speakers showing my amplifier 4 ohms...
  37. B

    Induced Current problem from review

    Homework Statement A 40 turn circular coil of a 4.0 cm radius and a total resistance of 0.20 Ω is placed in a uniform magnetic field directed perpendicular to the plane of the coil. The magnitude of the magnetic field varies with time as B = 50*sin(10π*t) mT where t is measured in s. What is...
  38. C

    Electromagnetic Induction and a coil of wire

    The magnetic field that is oriented perpendicularly through a 9.2 cm diameter coil of wire drops from 6.4 T to 6.1 T in 0.076 seconds. What is the emf induced in the coil? Trying to answer this. My question is, if they are perpendicular then does that mean that cos90 makes phi = BAcos theta...
  39. M

    Building a Tesla Coil: A Student Guide

    Hello everyone, I am interested in building a Tesla coil for fun and education. I am an EE student in my junior year of college, so I have most of the basics down, but I'd like to learn a little more so that I do not set my house on fire. I've been going through the principals of Tesla coils...
  40. V

    Voltage generated by a vibrating coil around a magnet

    Can I get the voltage generated by a vibrating coil around a magnet as a function of the frequency and amplitude of the vibration (given all necessary informations about the coil and magnet)? What would that function be? Also, what information about the coil and magnet would be sufficient and...
  41. F

    Ansoft Maxwell 15 Coil simulation

    Hello! I am a student of electrical engineering. I got assigned to a project where I need to simulate a coil in Maxwell 15 and a ball which floats in the magnetic field of the coil. This is for an experiment for demonstrating magnetsim, so my task is to find out what dimensions the coil needs...
  42. T

    Current flow in an MRI receive coil

    I am a physics student with very limited experience in electronics and I have been tasked with making an receive coil for use in an MRI machine. The design of an RF coil amounts to constructing to what essentially amounts to an LC resonator with a set resonance frequency. The design of my coil...
  43. D

    Optimizing Impedance Measurement: Bridge vs. Sine Wave Generator Method?

    Why don't we just connect a sine wave generator in series with a DMM and the coil, set the amplitude Δv0 to a given value on a scope, measure the RMS current I on the DMM and use Z = 0.707Δv0/I?
  44. R

    How the solenoid gets the linear motion when the current is passed in the coil?

    The Solenoids which are used for pneumatic controller uses the solenoid as a switch to control the value opening and closing. This is done by passing current to through the coil which produces the magnetic field . But i would like to know how the generated magnetic field will move the solenoid rod?
  45. B

    How To Design Solonoid Coil for AC Voltage

    Hello Friends, Can you help to solve the problem of my solenoid coil as before i created 12VDC coil & its working fine thanks for that help guys. but now i want 240 VAC solenoid coil. so can you please help me which SWG I have to select. how many turns have to select..i want the equitation how...
  46. Hijaz Aslam

    Electric Field of a circular arc at a point

    Homework Statement Given that the circular arc wire with radius 'r' has a linear charge density ##\lambda##. What is the Electric field at the origin? Homework Equations ##\vec{E}=\frac{kq}{r^2}## where ##k=9\times10^9## is a constant. 3. The Attempt at a Solution I took a small segment dy...
  47. Q

    How to measure the length of metal sheet coil?

    Hi everyone, I have been trying to find an equation to measure the length of a coil. The coil is a metal sheet that wraps around the loops as it creates. It looks like a roll of tape. I have been using two different formula, but it is not giving me the right results. 1. L = 0.065449 (OD^2 -...
  48. K

    Powering a Tesla Coil with a 12 volt battery--help--

    So I have been wanting to build a Tesla Coil for a while now, and I did not want to make a large one, just enough for a 4 or 5 inch spark. That being said I began searching the internet for designs when I stumbled upon the 12 volt battery variation. The idea is that the 12v battery would drive...
  49. A

    Why Isn't My Coil Simulation Achieving the Expected 8pT Signal in Maxwell?

    hello every one i want too simulate a coil with with Maxwell and transient solution type: this coil is in a paper and i want to simulate it i attach the coil properties. in this paper the dimension of coil is given such: diameret:12cm; length=84cm; moment=30a-m^2; construction= 16 turns...
  50. ilovescience85

    What is the resistance of a 0.2 H coil for a given time constant without prefix?

    Good afternoon all, I recently submitted a assignment and my lecturer has questions a figure i have put as an answer. Question was; An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply. Determine: the...
Back
Top