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. R

    Hallback Array Closed Loop Coil

    Hi all, I'm new to this forum and I'm not a physicist. I'm a Cabinet Maker looking for a career change. I performed an advanced search on the entire site and was surprised to find not a mention in regards to Halbach Array. My understanding is that the special arrangement of nib magnets can...
  2. J

    Can a Permanent Magnet Affect the Capacitance of a Coil?

    Hello, I've learned from my study of oscillator circuits that an inductor has some inherent capacitance in it due to the distance between the individual windings. I've heard somewhere that if you place a permanent magnet close to a coil that it will behave like a capacitor and I was wondering...
  3. L

    Magnetic field due to an elliptical coil

    Is there any expression for finding out the magnetic field due to an elliptical coil? Can we proceed with Biot Savart's law? If so what is the final expression?
  4. C

    Why Does an Aluminum Ring Levitate Above a Magnetic Coil?

    I don't know how to answer these questions. :( I know the alternating current makes the magnetic field changes. And the changing magnetic field generates emf.But I don't know why the emf is large enough to push the aluminum ring upward, and how come it goes up? thx a lot.
  5. W

    Induced EMF in N=181 Coil, A=.01955^2 at t=2.50, 7.50, 15.0, 25.0ms

    A magnetic field with the time dependence shown in Figure 23-38 is at right angles to a 181 turn circular coil with a diameter of 3.91 cm. What is the induced emf in the coil at each of the following times? (a) t = 2.50 ms 0 V (b) t = 7.50 ms (c) t = 15.0 ms...
  6. P

    Coil current physics homework

    I was wondering about the following problem: You are looking down on a single coil in a constant magnetic field B = 0.9 T which points directly into of the screen. The dimensions of the coil go from a = 6 cm and b = 15 cm, to a* = 20 cm and b* = 19 cm in t=0.028 seconds. If the coil has...
  7. M

    Effects of Doubling Primary Coil Current on Secondary Coil Induced EMF

    What would be the change of the induced emf in the secondary coil of a two coil system ( without ferromagnetic core ) if both the amplitude and the frequency of the current in the primary coil would double?: emf would stay the same emf would be halved emf would be 4 times larger...
  8. K

    How can Faraday's Law be used to calculate induced voltage in a coil?

    Hello, I am new here. I was hoping to get some help with a problem. I need to find the Induced Voltage in a coil in terms of the number of coils N, the length l, and time t. I think when all said and done the equation should look close to: NlcB0*sqrt(1-cos(kl)), which is the induced...
  9. L

    Calculate Impedance of Copper Coil w/ Iron Core

    I have to calculate the impedance (=R+j*w*L) of an infinite copper coil (par meter), with an iron core. Given data are the magnetic permeability, conductivity and radius of the copper wire, inside and outside radius of the coil, radius of the core and permeability and conductivity of the iron...
  10. M

    Calculating Max Emf from Electric Generator Coil

    Hello everyone, I'm confused on how to do this problem, it says: An electric generator contains a coil of 120 turns of wire formed into a rectangular loop 40.0 cm by 20.0 cm, placed entirely in a uniform magnetic field with magnitude B = 3.50 T and with B initially perpendicular to the coil's...
  11. C

    Coil Winding Mechanics: Deriving Linear Wire Speed Equation

    Hi folks! Long time listener-first time caller. I am building a coil winder for building my own transformers-fun fun! Anyway, I came across an interesting aspect associated with winding which, if not for anything else, provides an interesting math physycs problem. I am trying to understand what...
  12. T

    Inductance of a coil in an AC L-R circuit

    Does the formula tan (phi) = (wL - 1/wC)/R work without a capacitor? Can I turn it into tan (phi) = wL/R instead? I don't know what formula to use to find the inductance of an inductor in this question: A voltage source V = 160V sin (100t) is connected in series with an inductor and a 17.0...
  13. P

    16-Year-Old Seeks Help Building a Coil Gun

    Hey! Im 16 and love physics, but I am starting to get board with the regular school course and want to start a little project of my own, i thaught a coil gun would be a good start:biggrin: . Any way, I've looked on google on how to make one but all the instructions suck so i was wondering if...
  14. J

    Inductance of a coil for a given emf and current change

    Hi, My Question: What is the inductance of a coil if the coil produces an emf of 2.50V when the current in it changes form -28.0 mA to 31.0 mA in 12.0 ms? For this I know I will need to use this equation: E=-M(delta I)/(delta t) My problem is that I was wondering if coming up...
  15. T

    How do you find the resistance of a coil

    A coil is to be used as an immersion heater for boiling water. The coil is to operate at a voltage of V and is to heat an amount of water with a volume of v by T degrees C in a time interval of t seconds. Use 4190 for the specific heat capacity of water and 1000 for the density of water. How...
  16. I

    Does the speed of a wave in a spring depend on the maximum speed of each coil?

    Hi again. I'm going crazy over this question. Does a longitudinal wave in a spring depend on the maximum speed of each coil? Me, I've always thought that the transverse velocity of the Particle or coil remains constant and independent of the wave speed itself. Am I wrong? Or did I misunderstand...
  17. z-component

    Building a Tesla Coil for My High School Graduation Project

    My school district requires that each high school senior complete what's called a "Graduation Project," in which the student makes a project of their choice that relates to their academics. There's no specific requirements about the actual project, just the completion of different components...
  18. J

    What is the magnitude of the magnetic field at the center of the coil?

    Alright there is a problem I was given and it has four parts, I got the first two but am having trouble with the last two. A)Consider a circular current loop of radius 10.5 cm with 200 total turns. Assume that the current through the coil is I. What is the magnitude of the magnetic field at...
  19. W

    Engineering Help: Find the Integral for a Wire Coil

    i am looking for an equation (integral) , so that i can predict what width to make a coil of wire , of certain length ,and thickness, so that it comes out to an outer diameter of 1.5" with an inner diameter of .5".. i usually spend my time in the engineering section , but i thought that i would...
  20. M

    Mysteries of a simple spiral (coil).

    Let we have a piece of wire, copper, for example. Let we have the generator of alternating current with changing frequency. We connect the ends of a wire to clips of generator of an alternating current and then turn it “ON”. Resistance of a piece of wire does not depend on frequency of a...
  21. S

    Rectangular coil in a galvanometer

    Good day everyone, I was wondering how would you determine the magnetic field within a square coil? My colleague and I are trying to write a lab up on tangent galvanometers, but all we can find are models with circular coils, and ours is square. Any help is appreciated.
  22. N

    Metal ring repelled from AC coaxial coil

    I thought people helped on this forum? If anything is unclear just ask, I'm checking for posts every minute. Come on people I have to get this done by 5 pm. I've gotten a little further. I believe it has something to do with mutual inductance. A metal ring (no current) is brought close to a...
  23. L

    Finding Quantitative Proof of Optimal Helmholtz Coil Separation

    I'm trying to track down a quantitative proof that the most uniform magnetic field between two Helmholtz coils occurs for a separation equal to their radii. So far I've just been playing around with the Biot-Savart law and proving that B is identical at several trial points along the axis...
  24. R

    Understanding Magnetic Induction Field B on Circular Coil Axis

    Just a quick question about finding the magnetic induction field B on the axis of a circular coil shown on page 7 on http://www.physics.gla.ac.uk/~dland/ELMAG305/Elmag305txt5.pdf I understand why the field must be along the x-axis but why does (dlxr )x become dlrsin(alpha)? alpha doesn't seem...
  25. M

    Generators (know r, l, B, angular speed of coil) how to find peak EMF?

    The coil of a generator has a radius of 0.14 m. When this coil is unwound, the wire from which it is made has a length of 5.7 m. The magnetic field of the generator is 0.20 T, and the coil rotates at an angular speed of 25 rad/s. What is the peak emf of this generator? Please help me get...
  26. M

    Magnetic force on coil problem

    I'm stuck on the following problem: A long thin coil of length l, cross-sectional area S, and n turns per unit length carries a current I. It is placed along the axis of a large circular ring of radius a, which is carrying a current I'. If d is the displacement of the center of the coil from...
  27. L

    Magnetic field coil of wire problem

    This is the problem taken from Giancoli Chapter 20, number 80: The magnetic field B at the center of a circular coil of wire carrying a current I is : B = \frac{\mu_{0}NI}{2r} , where N is the number of loops in the coil and r is its radius. Suppose that an electromagnet uses a coil 1.2m in...
  28. G

    B-field produced by a spiral coil

    Howdy I'm having a ton of trouble with this question Basically I have a spiral coil running around the z-axis with radius 'a' height '2b' and pitch 'c'. The point (x,y,z) = (a,0,0) is on the spiral and n = 2b/c (that's the number of turns on the spiral). There's a steady current running...
  29. S

    Question regarding mutual inductance of two coil

    I have my question,solution and the problem I faced in the attachment that followed.Thanks for anybody that spend some time on this question.
  30. S

    Need help with torque on a rectangular coil

    This is another question that I have think for very long hours but still find the solution to this question.I have my question in the attachment that followed.
  31. S

    Need help with torque on a rectangular coil

    i have think very long on this question but still can't figure out what is meant by the question.I have my question and my doubt on the attachment that followed.
  32. L

    Television steering coil control circuit

    Hi. I'm trying to find information about the circuit which controls raytracing within a television CRT tube (the circuit which controls the current through the steering coils deflecting the beam up down left and right)... How is this precise raytracing accomplished... what type of circuit is...
  33. P

    Measure the resistance of a coil of wire using a voltmeter/ammeter

    hey everyone. physics doesn't make sense to me. i need help (!) esp. since I am considering choosing it on highlevel in the IB Diploma programme I am in right now. anyway. so i have to answer this question for the class on wednesday, but I am totally lost. i would appreciate it a lot if...
  34. R

    How Is Average EMF Calculated in a Rotating Coil?

    A closely wound, retangular coil of 80 turns has dimensions of .25m x .4 m. The plane of the coil is rotated, in .06 sec from a position where it makes an angle of 37 degrees with a magnetic field of 1.1T to a position perpendicular to the field. What is the average emf induced in the coil...
  35. D

    Primary coil is used to overcome the back e.m.f

    I was told that P.d. supplied to the primary coil is used to overcome the back e.m.f. so that the the flux will keep changing, why is it so? What happened if the P.d. supplied is different to the back e.m.f.? Thx!
  36. S

    Building a Tesla Coil for a School Science Fair: Tips and Advice

    I want to build a tesla coil for my school's science fair. Is there some way you can make the Tesla coil safe and not extremely dangerous and deadly? I don’t want to kill myself :eek: ! Does anyone have any tips or advise? ~Thanks
  37. K

    Voltage pulse from ignition coil ?

    Voltage pulse from ignition coil ?? Hi, Does anyone know the voltage of the pulse from a typical ignition coil? thanks. tyler
  38. M

    Generators: Water instead of a coil?

    Yea, I just had a pretty weird idea, can we instead use water instead of a coil since water is a conductor as well (impure water that is.). Can we instead rely on convection currents or water waves to power this generator?
  39. D

    Force within coil: compression or expansion?

    A coil of wire is formed of many loops. These loops, though tracing a circular path, may be though of as being parallel to each other. We know that whenever parallel wires carry and electric current, there will be a mechanical force generated between those two wires. When electric current is...
  40. T

    Radio Tuner without an inductor coil

    A friend and I are trying to build a radio controlled airplane, but an LCR circuit tuner would be too heavy. Does anybody know of a way to make a tuner without an inductor coil? Any help would be appreciated.
  41. J

    Electromagnet pulse coil powered by static charge

    Hello, I have a question concerning electromagnet coils and static electricity. If one were to generate a static charge and store it up some how (like in a Leyden jar or something), and that charge was then dumped over a small electromagnet, would there be enough energy to provide a small...
  42. U

    Electricity Generated by Magnet Motion Over Coil

    A small coil is laid on a flat table and a magnet is held vertically over the magnet. Both are stationary. I move the magnet so that it passes the coil and then held it stationary again. I move the magnet over the coil and hold it stationary there again. What am I supposed to conclude about the...
  43. tandoorichicken

    Is the Emf in a Coil of 100 Turns 0 When B Field Decreases from 1.0 T?

    Please tell me if this is right: A coil contains 100 turns of wire in a loop 15cm in diameter. The loop is placed between the poles of a large electromagnet B= 1.0 T, with the plane of the loop perpendicular to the field. If the magnetic field is steadily reduced from 1.0 T to 0 in 16...
  44. Y

    Magnetic field-determine the plane of coil makes with verticle

    a long piece of wire with a mass of 0.100kg and a total length of 4.00m is used to make a square coil with a side of 0.100m. the coil is hinged along a horizontal side, carries a 3.40-A current, and is placed in a vertical magnetic field with a magnitude of 0.0100T. (a) determine the angle that...
  45. M

    Calculating Induced EMF in a Changing Magnetic Field

    Ok, so here's the problem: Induced EMF A 5.80 cm diameter wire coil is initially oriented so that its plane is perpendicular to a magnetic field of 0.770 T pointing up. During the course of 0.140 s, the field is changed to one of 0.240 T pointing down. What is the average induced emf in the...
  46. Jonathan

    Measuring Self-Capacitance & Self-Inductance of a Coil

    the self-capacitance and self-inductance of a coil? Are there equations for these where I won't need to know the number of turns? Since I think #2 is no, are there meters I can buy to measure this, or can I use the measurements from a volt/resistence meter I already have?
  47. S

    Plastic disc with a coil wound around is axis of rotation

    A question, I have a plastic disc with a coil wound around is axis of rotation. The coil carries current I. Now the disc carries charges at its circumference. Now the current flowing in the coil is brought to 0 instantaneously. This creates Electric Field to be produced that travel in...
  48. D

    Finding the Inductance of a coil

    I'm stumped by the following problem. To determine the inductance of a coil used in a research project, a student first connects the coil to a 12.0V battery and measures a current of 0.630 A. The student the connects the coil to a 24.0-V(rms), 60.0-Hz generator and measures an rms current of...
  49. D

    Watching Light Travel in a Coil: Is It Possible?

    my uncle was describing something that showed light traveling at a slow speed and i had no idea how it worked. he said it was a clear solid plastic like tube wrapped around in a coil and when you shined a light in one end you could watch it enter the coil, spin around the coil, and then exit...
  50. A

    Would the Induced Current Change Direction Inside a Solenoid with a Search Coil?

    if we were to insert a search coil inside a solenoid, (plane of coil perpendicular to B), would the induced current change direction in the middle of the solenoid ? it would have to wouldn't it since it would now be approching the opposite pole --- ??
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