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. M

    Oscillation of a coil in a Magnetic Field

    Homework Statement Hi I am really stuck on this question. It got handed out to us this morning and is due in Wednesday of this week. Any help would be great thanks. A circular solid coil consisting of a circular disk of radius R = 20mm and mass M = 50 g pivoted through its diameter. It has...
  2. R

    Max Voltage Induced in Rotating Coil

    Homework Statement A square coil (25 x 25 cm) that consists of 50 turns of wire rotates about a vertical axis at 1000 revolutions per minute. The horizontal component of the Earth's magnetic field at the location of the coils is 2 x 10-5. Calculate the maximum voltage induced in the coil by...
  3. T

    Tesla coil not working (help anyone?)

    Hi All, Long time reader, first time poster. I'm currently building a tesla coil. here are the details: 1.) I'm using three parallel NSTs that each output about 6500 volts at .9 amps. 2.) I'm using 4 high voltage capacitors that I built using two sheets of aluminum siding with...
  4. T

    Mutual inductance of a coil and straight wire

    Homework Statement A single rectangular loop is placed distance C from a wire of current I. The dimensions of the loop are BxA. The loop and wire both lie in the same plane, and a is at right angles to I. Derive an expression for the mutual inductance, given that you found flux in a previous...
  5. P

    How Does the Length of a Yoke Affect the Inductance of Yoked Coils in Series?

    When finding for "L" is the value for "l" (length of coil) affected by the length of the core material. Or more specifically when one is working this equation for two coils yoked in series do you figure each coil separately?...and if NOT, do you include the length of the yoke? Here is a link...
  6. E

    My IEC Contactor Coil keeps overheating

    I have a 3ph IEC contactor with 120v coil voltage. For some reason, the coil starts heating up like crazy when I run it. I have 121v on L1, 120v on L2 and 121v on L3. I re-connected all the wiring to make sure there were no loose connections but still it keeps heating up when I energize the...
  7. R

    Calculating Induced Current in a Coil of Wire

    Homework Statement A flat coil of wire consisting of 20 turns, each with an area of 50 cm2, is positioned perpendicularly to a uniform magnetic field that increases its magnitude at a constant rate from 2.0 T to 6.0 T in 2.0 s. If the coil has a total resistance of 0.40 Ω , what is the...
  8. T

    Magnetic field: Bar magnet & coil. Number of Turns?

    Hey all, I'm new to this site, so bear with me here! First post woot! Homework Statement A bar magnet with magnetic dipole moment 0.5 A m2 lies on the negative x-axis, as shown in the diagram. A compass is located at the origin. Magnetic North is in the negative z direction. Between the bar...
  9. A

    Find the inductance and a current of a coil

    Hi everybody, i have got a question,any help will be much appreciated A ferrite ring core has a slot cut in it such that the plane of the slot contains the axis of the toroid. It is wound with 26 turns. i have attached the picture of the this problem. Relative permeability = 680 Bsat...
  10. E

    How can I transmit a static frequency through a copper wire coil

    I am trying to figure out how to program a 528 hz signal to emit and amplify through a copper wire coil
  11. M

    Quick induction coil question

    Hi guys, quick query (at least I think it's quick!). I know that, in a microphone, when a waveform passes through the electromagnetic field it resonates the diaphragm and in turn moves the induction coil set in the middle, creating a VARYING current... My question is: Is the varying...
  12. C

    How Is Torque Calculated on a Rectangular Coil in a Magnetic Field?

    Homework Statement A rectangular coil consists of 25 turns of wire forming a square 4cm each side. By considering the force on a current-carrying straight wire, calculate the torque acting on the coil when the normal is at 30 degrees to a magnetic field of 0.8T and 12 A are flowing...
  13. P

    How much will the speed of a magnet be reduced when it is passed trough a coil?

    I need some help to calculate the retardation of a magnet cylinder passing trough a coil with an open end which lies horizontal. If you have a 0.5 m long circular coil which is 50 mm in diameter and a circular magnet cylinder fitting into the rod. The magnet cylinder has an initial speed of 10...
  14. J

    Magnetic field of elliptical coil (at all points in space)

    Homework Statement What I actually need to find is the magnetic field at any point in space for an elliptical solenoid. I think the way to do this would be to find the magnetic field caused by an elliptical current loop, and then to use some kind of summation for multiple loops to get the...
  15. P

    Creating a Nichrome Heating Coil for 12V, 36W @373K

    Homework Statement A heating coil is to be made, from nichrome wire, which will operate on a 12 V supply and will have a power of 36 W when immersed in water at 373 K. The wire available has a cross-sectional area of 0.10 mm². What length of wire will be required? (Resistivity of nichrome at...
  16. R

    Tesla Coil Plasma: Can It Make Music?

    Okay, now I realize that this is from sci-fi, but I'm just wondering if it's possible to do this. In the movie, The Sorcerer's Apprentice, the guy uses Tesla coils to "make music." He said that when they fired, the did so at such a high frequency that it made sound. Is this possible?
  17. J

    Two Phase Power For Contactor Coil?

    Is anyone able to explain why someone wired this motor contactor circuit such that activating the coil is done by connecting the two leads to the following: contactor: Allen-Bradley 69A86 lead 1: 120V AC lead 2: 120V AC - Phase Shifted by 120 degrees So I guess the difference of the...
  18. C

    Tesla Coil Surprises Inside a Faraday Cage

    When this guy gets inside the Faraday cage and they hit it with like 200,000 volts from a Tesla coil , when he is inside the cage he can touch the inside and not get shocked , so basically the charge flows on the outside , is this because the electric field from all around the circle pushes...
  19. AJ Bentley

    Wavelength dependence of a resonant coil?

    This question relates to the design of a Tesla coil, which is basically a loose-coupled, tuned transformer. The secondary is a series LCR circuit that develops a high voltage across a capacitor. The capacitor takes the form of a toroidal 'top-load' to ground. In the literature, much...
  20. S

    Stator ring coil and connection questions

    Hello everyone: I am trying to find a program or formula that will help me figure out how many windings, turns of coil, are needed per coil on a 6 coil steel stator ring powered by 3-phase AC power to get a certain magnetic field strength, about 1.3T. Is there any way that you could help me...
  21. A

    Magnetic field inside a sperical coil

    Homework Statement What is the induction in the centre of a spherical coil with N turns, the current I and the radius R? Homework Equations Biot-Savart law \mathbf{B} = \int\frac{\mu_0}{4\pi} \frac{I d\mathbf{l} \times \mathbf{\hat r}}{|r|^2} The Attempt at a Solution I know what...
  22. E

    Mutual Inductance: Coil 1 Excited, Coil 2 Open Circuited

    I have a very basic question regarding mutual inductance. Consider a basic square loop with two coils wound on opposite sides from each other, with coil one excited while coil two si left open circuited. The total flux linking coil 1 is Φ11 = Φl1+Φ21 where Φ11 is the total flux...
  23. V

    Determining the constants R and L of a coil

    We determined the constants R and L of a coil by placing it in series with a standard resistor of 10 ohms and reading the voltages on the terminals of Rs, the coil and the series circuit complete. What are the values of R and L for the following voltage readings at 60 Hz: Vrs = 20; Vcoil =...
  24. W

    How can I simulate a helix coil with current in COMSOL Multiphysics?

    Hello ! I am using Comsol Multiphysics in order to simulate the eddy currents in a damaged/cracked steel circular rod, with a helix coil surrounded it and thus creating the alternativ magnetic field. Actually, I am having a lot of problem in modelling it, mainly because I am new in using...
  25. H

    Measuring the frequency-dependency of the resistance of a coil inductor

    0. Bit o' background + greeting Hello everyone. I am a third-year math/physics/CS/AI major and I've never used this forum before, as can be seen from my impressive post count. I enjoy leafing through it though and find myself perpetually impressed by the activity and commitment of the community...
  26. K

    Resistor, capacitor and coil with Alternating current

    Homework Statement A problem from a translated Sears-Zemansky, 1965, 14-10: A conduction coil with inductance of 15 miliHenrys and resistance of 10 Ohms, is connected in line with a capacitor of 200 microFarads and a resistor of 12 Ohms. The circuit is supplied with an alternating current of...
  27. T

    Why does induced current in loop vary twice with rotation of coil?

    A square loop of wire of side a is rotating with frequency \omega in a magnetic field. I understand that at time t, a magnetic field B=B_{0}sin\omega t passes through the loop. But why does the current induced in the loop vary twice with the frequency of rotation? What is the expression of...
  28. Sirsh

    How do you calculate the resistance in a coil?

    Hi all. I'm just wondering if it is possible to calculate the resistance in a coil without the amperage value? I've got voltage,coil-diametre, amount of turns, coils material type. The only way i think it is possible if i set a ampmetre into the circuit. is there any way? Thank you.
  29. H

    Basic Coil Turn question please see

    Homework Statement 200-turn,coil of 8.0cm length is made of 0.50mm-diameter copper wire. Magnetic field is perpendicular to coil. At what rate B should increase to induce a 2.0 A current in the coil? Homework Equations The Attempt at a Solution i am not getting anthing
  30. T

    Exploring Faraday's Law of Induction with a Rotating Coil

    Homework Statement A flat square coil of N turrns and area A is rotated at an angular velocity w in a uniform magnetic field of strength B. The rotation axis is perpendicular to the magnetic field direction. The coil is connected to a Galvonometer using suitable slip ring connectors and the...
  31. K

    A conduction coil and 2 resistors

    Homework Statement a conduction coil with 2 resistors are connected, according to the drawing. write the expression for the potential difference Vac over the coil after t seconds after the switch is closed. Homework Equations The current at any time: (a) i=I(1-e-Rt/L) The electro motive...
  32. T

    Biot-Savart applied to rectangular coil

    Homework Statement A rectangular current-carrying coil, with side lengths a and b has N turns. The current, I is stable. The coil is shorter than its width. Calculate the magnitude of the magnetic field at the centre of the rectangle. Homework Equations The law of Biot-Savart (I think)...
  33. JJBladester

    Electromagnet within a coil

    Homework Statement Hooking up voltage to a solenoid (coil of wire) creates an electromagnet. Moving the electromagnet in and out of a larger coil hooked up to a galvanometer creates an emf (voltage) in the larger current. Does an emf get created for a *stationary* electromagnet inside a...
  34. S

    Magnetic flux generated by a motor coil

    Hi, I am not so good with magnetic equations and I am needing some advice in how to start to calculate the magnetic flux generated by a motor coil. Finally I want to be able to calculate the magnetic flux generated with and without the iron core of each coil in the motor. I will...
  35. S

    Current carrying coil - torque on a circular one

    Hello, Could someone please either verify my proof or find the error in it - its driving me nuts! if Torque (T) = Fd but F = BIlsin theta and F changes as you move around the circle 1. therefore to find F on the semi-circle: \int between 0 and pi of BIlsin theta d theta = 2BIl ...
  36. K

    Coil length or Solenoid length?

    This is not a homework. I am just pretty confused about a problem (with solution!) I saw in the internet found here: http://www.transtutors.com/physics-homework-help/electromagnetism/Electromagnetic-induction.aspx The part I am confused is the mutual inductance part. Here I repeat the question...
  37. R

    Helmholtz Coil Problem: Analyzing Magnetic Field at Point Z

    Homework Statement The diagram illustrates a Helmholtz coil, consisting of two identical circular coils of wire, each one having N loops and carrying the same current I. The radius of each coil is R, and the two coils are R meters apart. (a) What are the direction and strength of the...
  38. F

    Iron core for Electrostatic coil

    I am just an electrician doing experimental work with a Stubblefield coil. From what I've read the most common steel is 1018. If Stubblefield used a common bolt I assume this would fall into the 1018 realm. Would the 1018 iron core be better cold rolled or hot rolled for the magnetic collapse as...
  39. S

    Jackson's 5.35: Insulated Coil on a Sphere

    Homework Statement The question is Jackson's 5.35. Insulated coil on a sphere (radius a) to generate uniform field B0 in the z-direction inside the sphere and dipole field outside the sphere. Conductivity is \sigma and permeability is \mu. 1st question is to find the surface current K and...
  40. D

    Solve Parallel Resonance: L&C Values & Resistance of Coil

    When placed in series a coil and capacitor resonate at a frequency of 2251Hz and when placed in parallel they resonate at a frequency of 2228Hz. At parallel resonance it is also found that a current of 5mA flows from the supply when the supply voltage is 25V r.m.s. Determine the value of the...
  41. L

    Induced EMF in a coil problem

    1. A 100-turn, 2.0-cm-diameter coil is at rest in a horizontal plane. A uniform magnetic field 60 degrees away from vertical increases from 0.50 T to 1.50 T in 0.60 s. 2. EMF = N*d(phi)/dt phi = flux = ABcos(theta) 3. dB/dt = 1/0.6 EMF = 1000*(1/0.6)*pi*r2*0.5 = 0.262 V Is...
  42. N

    Question about magnetism/induced emf in small coil

    Homework Statement A solenoid with a length of 25.0 cm, radius 1.60 cm and 5500 turns carries a current of 1.50 A. A small coil of radius 1.05 cm and 130 turns is placed at the center of the solenoid with its axis in the same direction as that of the solenoid. A 470 ohms resistor is connected...
  43. Y

    Generator connected to transformer- Find angular speed of coil

    Homework Statement A generator consists of a circular coil of radius 0.2 meters wrapped 10 times and is spun in a uniform magnetic field of 0.38 Tesla. It is connected (on the primary side) to a transformer with 7 turns on the primary side and 20 turns on the secondary side. If the secondary...
  44. A

    How to Design an Amplifier for a Rogowski Coil?

    hiii guys im doing my FYP on amplify the voltage from a rogowski coil just to make it short i have already design the coil which can detect a 50k frequency and gives pick-to-pick = 10mV Ac now, i have to design an amplifier that can give an actual value. so, i have already got a...
  45. V

    Tesla Coil Help: Get Answers to Your Questions Here!

    Hello everybody! :D Im building a tesla coil for a science fair and needed some help with it. For the toroid, I got a rubber pipe which I intend to bend to a toroid and wrap with aluminum tape. Will this work? How will it be different if I use a metallic sphere? Also, for the spark gap...
  46. L

    Amplitude of the induced voltage across the coil

    If anyone can advise that would be great. 1. The plane of a 5 turn coil of 5mm² cross sectional area is rotating a 1200 r.p.m in a magnetic field of 10mT. Q. Calculate the amplitude of the induced voltage across the coil Data: 5 turns c = 1200 rpm A = 5cm² B = 10 mT 2. φ =...
  47. K

    Finding EMF Required for a 22A, 5 Ohm Heater Coil

    Homework Statement A current of 22 amperes flows in a heater coil whose resistance is 5 ohms. What E M F in volts is required? Homework Equations The Attempt at a Solution Not quite sure where to begin. I'm thinking the internal resistance, R, is inherent w/the circuit so EMF...
  48. D

    Moment of Inertia of a uniform rectangular coil

    Homework Statement A uniform rectangular coil of total mass 270 g and dimensions 1m x 5m is oriented perpendicular to a uniform 4.00-T magnetic field (the figure ). A current of 2.90 A is suddenly started in the coil. Homework Equations angular acceleration = torgue / moment of inertia...
  49. N

    Magnetic Force in a current carrying coil

    Homework Statement A rectangular loop with length of l = 0.30 m and width w = 0.12 m and a mass of 25-grams falls (from rest) a distance of .28 m before entering a constant magnetic field that points out of the page. The internal resistance of the wire is 5.5 \Omega. (i) What is the speed of...
  50. S

    What is the induced emf in a coil with changing magnetic field?

    Homework Statement A coil is wrapped with 247 turns of wire on the perimeter of a square frame of sides 27.3 cm. Each turn has the same area, equal to that of the frame, and the total resistance of the coil is 2.53. A uniform magnetic field is turnedon perpendicular to the plane of the coil...
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