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. B

    Torque on a rectangular coil in a uniform magnetic field

    So this was a section taken out from a question which I am trying to do shown below I have drawn a sketch to help me visualise of what is going on I have used Fleming's left hand rule to help me determine what direction the force is facing on each side of the coil. For the last part in...
  2. rayjbryant

    Calculating the terminal velocity of a magnet falling through a copper coil

    The magnet being used % magnet dimensions [m] d = .0127; r = .00238; %mass of magnet [kg] m_w = .0017; % other constants u_0 = 1.26E-6; % permeability of free space constant T m/A g = 9.81; % gravitational constant in/s^2 %coil properties [22 gauge wire] [m] a = .00635; %radius w =...
  3. Adesh

    Why does the current have no ##\phi## component in a toroidal coil?

    These are images from the book Introduction to Electrodynamics by David J. Griffiths . . . My problem is that I'm unable to understand how the current has zero ##\phi## component (I have underlined it in the first image)? I do understand cylindrical coordinates, I know...
  4. A

    When is the flux through a coil from a bar magnet zero?

    Suppose I have a finite sized cylindrical bar magnet of radius $a$ and length $b$. It is coaxial with the $x$ axis and moving from $-\infty$ to $\infty.$ A circular closed wire of radius $r>a$ is in the $y-z$ plane with center at the origin. When the bar center of the bar magnet passes through...
  5. B

    Calculate the charge flowing in the coil if the field is removed

    Hello So here is my question Not so sure how to approach this question This is what I have worked out so far which is the magnetic field strength of the solenoid, not sure if this comes in helpful though Thanks for any help!
  6. N

    Electromagnet Coil Performing Poorly

    I recently posted about an air cored electromagnet I was designing. It currently uses 300' of 17 AWG magnet wire, coiled around a .5'' diameter tube. I purchased a DC to DC step up to test different voltages and currents. I noticed while using it that regardless of what current I supplied...
  7. L

    Basics of RF coil development for MRI

    Hi all, I'm trying to understand basics of radiofrequency (RF) coil development for magnetic resonance imaging (MRI). For example, the problem is to develop simple surface single-loop RF coil tuned to 100 MHz. In program Coil32, I set the following parameters: diameter of the loop D = 20 mm...
  8. Y

    Electromechanical Systems: Determine the voltage across a moving coil

    Homework Statement: Figure shows two mutually coupled coils, for which L11= L22 = 3 + 2/3x (mH) L12 = L21 = 1/3x (mH) where x is in meters, (a) If i1 = 5 A dc and i2 = 0, what is the mutual electrical force between the coils at x = 0.01 m? ( b ) If i1 = 5 A dc and the second coil is...
  9. D

    I tried building an induction coil

    i tried to build an induction coil. the input voltage is 12.1 volts. the output voltage is 16.5 millivolts maximum. so the voltage in the primary coil is 12.1 volts. the voltage in the secondary coil is 16.5 millivolts maximum. the induction coil consist of a nail. thicker coils form the...
  10. jerromyjon

    High voltage coil discharge polarity for vehicle spark plugs

    I've recently had a discussion with fellow technicians in the automotive industry about spark plugs and some systems having "opposite polarity" on the ignition coils. (specifically the secondary coil which sends the high voltage pulse to the plug which sparks the fuel) Common sense tells me...
  11. K

    Efficiency of heating up aluminum vs steel by induction

    Summary: In a heating by induction experiment performed, the idea was to determine the efficiency of heating up a small steel cylinder, an aluminum cylinder and then compare the two efficiencies. The cylinder was surrounded by a metall coil that alternating current was going through...
  12. garthenar

    Power related to the EMF of an adjustable coil in a magnetic field

    I'm already stuck on A. I'm hoping once I figure that out the rest will just fall into place but be prepared for this to take awhile. I understand how to use Faraday's law to get the current or voltage of the system based off the movement of the bar but I have no Idea how to relate the rate of...
  13. cnh1995

    Engineering Frequency of operation and Q factor of a coil

    My reasoning: Initial Q factor Q1= X1/R After doubling the frequency, reactance also doubles. So, Q2= 2(X1)/R. Hence, Q factor doubles (option a is out). Now, since it is mentioned that the coil has high Q factor, I assumed X >> R and hence, total impedance is approximately equal to the...
  14. M

    Calculating the torque of the Laplace force on this coil

    We first determine the Laplace force for each value ##\alpha##. $$F_{\alpha} = 5(0.3)(0.4)\sin(\alpha) = 0.6\sin(\alpha) \ \text{N}$$ We then calculate the torque at angle ##\alpha##. $$\tau_{\alpha} = \frac{a}{2} F_{\alpha} = 2.5 F_{\alpha} \ \text{N.m}$$ Then we just plug in ##\alpha## and...
  15. gdritz

    Molten metal temperature vs Induction Coil Current

    Hi guys, I'm new here. I have been analyzing the behavior of cast iron melts in induction furnaces and realized that at the end of the melt the current increases slightly. The power remains the same. Physically, does anyone know the reason? I imagine to be related to the magnetic permeability...
  16. T

    Utilizing Fan Coil Unit return to fullfill fresh air requirements

  17. dedocta

    I FRB's source as Rail and/or Coil Guns (or mass drivers)

    Summary: FRB's source as Rail and/or Coil Guns (or mass drivers) Hello, I've been studying rail and coil guns recently, and certain applications of this technology can result in some pretty high speeds with a significant amount of mass. I've been wondering if these FRB's could be a result of...
  18. J

    B Coil + zinkplate + copperplate + 9V battery = shock

    So I just connected a zinkplate and a copperplate in series with a battery 9v and a coil(with a an iron core). All the parts are from a set bought for learning about electricity. Since I was a kid I have many time put the + and the - of a 9V battery on my tongue, and felt the electricity. So...
  19. brainbaby

    Role of the capacitor, coil and choke in this television receiver design

    Hi friends, I am studying this circuit which is the first all electronic television receiver created by Dr. Farnsworth back in 1927. Triode are being employed along with some caps and coils. The design is very simple and clear, basically this receiver is a detector circuit which detects the...
  20. D

    I Electromagnetic Fields and the manipulation of Space-Time

    Summary: Mathematical and Physical queries in regards to Electromagnetic Fields and their manipulation of Space-Time. I recently started looking into Einstein's Field Equations, to get a better understanding of how mass distorts and curves the plane of Space-Time, however from doing this I...
  21. P

    How to calculate the voltage induced in a coil by an AC magnetic field?

    So, as it says in the title, I am trying to calculate overall voltage induced in a coreless coil in the cases of it being stationary and moving in an alternating magnetic field. To go more into detail, I would like to create a mathematical model of a coil in an alternating magnetic field that...
  22. Charlie Cheap

    Will switching to a lower resistance resistor damage my coil on long trips?

    I have stated here before I run a points distributor in my 200 Ford six but usually with a Pertronix conversion. After finding a later 200 head (1973) I plan to have it machined for a direct fit 2-barrel carb. Now I am using a 2-barrel adaptor and I want as much spark as possible at the plugs...
  23. mariost

    Electrical How Did I Safely Build and Use a Tesla Coil for Entertainment and Education?

    A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce high-voltage, low-current high frequency alternating-current electricity. Tesla tried to transfer energy with a wireless way. It was really difficult...
  24. M

    Coil and resistor in parallel -- How to calculate the phase angle?

    Hello. So I have a coil and a resistor in parallel connection. It is powered by alternating current. I have to calculate angle between voltage and current, what is the formula? I know the reactive resistance in coil, I know resistance of resistor, voltage across both of them and amps flowing...
  25. Zack K

    Forces acting on a coil due to a varying magnetic field

    I don't understand why a force would be acting on this rectangular coil at all. The magnetic field of the wire would only induce a force on the coil, if the coil had a current flowing through it. At first I would think that the electric field from the varying magnetic field would induce such...
  26. J

    Calculating Charge on Capacitor with Decreasing Magnetic Field & Coil

    Where should I start?
  27. Zack K

    Current induced on a coil by a changing magnetic flux in another coil

    I will first calculate the magnetic flux of the coil in motion. $$\frac {d\phi}{dt} = -\frac {dB_{loop}}{dt}A = -\frac{d}{dt}(\frac{\mu_o}{4\pi}\frac {2\pi NR^2I}{(R^2+z^2)^{\frac{3}{2}}})A$$differentiating in terms of ##z##, we get $$\frac {d\phi}{dt} =(\frac{\mu_o}{4\pi}\frac {6\pi^2...
  28. noxidINF

    Motor drive a coil in a magnetic field to power itself?

    Hello Friends, I have been wondering, is it possible to construct a motor, and attach a coil to it, such that with the motion due to the rotation of the motor, it generates a excess of energy that can be used to power the motor in turn, basically, could i use the excess to charge a battery that...
  29. puya

    Magnetization of a Helical coil in a Reservoir of parrafin

    To test an Experimental Model , my advisor said to make this investigation; I have a Reservoir of parrafin, Capacity is 50 liters, Around this Reservoir there is a Helical copper Pipe, I have to magnetize the Reservoir by using Helical coil . Many thanks For your assistance
  30. L

    Loading/charge time of an electromagnet

    Hej Guys, Did anyone see anywhere an equation to this? If nothing else then a loading time formula for solenoid would do. Thank you!
  31. A

    Electrical Why isn’t this Tesla coil working?

    Hello all! I have made a Tesla coil using a proven circuit I found online but what I have made isn’t working here is a picture please help. PS: yes I know it is fairly messy but the specs are as fallows: B50k potentiometer One green 5mm led One 200ohm 1/4 W 5% resistor Primary coil is 8...
  32. A

    B Calculating the Uniform B Field in an AC Helmholtz Coil: What's the Formula?

    What would be the formula to calculate the right spacing distance between the coils in order to get a uniform homogeneous B field in the middle of the coils and how to determine the B field strength? I can only find bits and pieces on google about these sort of formulas but their intended for...
  33. kancharla_g

    Where can I find Laminated sheets for coil core

    I need to buy a 'I' shaped CRGO laminated core sheets, is there any website where I can buy online? Thanks
  34. marino

    Power generated by a coil rotating in magnetic field

    The problem: a coil of radius r, length l and N turns, rotating with constant angular velocity ω around an axis perpendicular to its simmetric axis and passing for the center of the coil. The coils is submersed in a static magnetic field, intensity B0, perpendicular to the axis of rotation of...
  35. S

    Force in a magnetic field on a moving coil

    Homework Statement A square coil (sorry, its not "current carrying" as shown in diagram, my mistake) of length L is released from rest, in a horizontal uniform magnetic field going into the plane of paper, of length 2L. What can you say about the coil's acceleration? Homework EquationsThe...
  36. Celso

    Induced EMF — generator coil area calculation

    Homework Statement What is the necessary area for a generator that produces an emf of ##\mathcal{E} = 150V## when it spins at a ratio of 60 revolutions per second, in a magnetic field of ##B = 0.5 T##? Homework Equations ##\oint_{c} E \cdot dl = \mathcal{E} = -\frac{d}{dt}\iint_{s} B \cdot dS...
  37. betamu

    Flux through a coil due to Self-Inductance

    Homework Statement A coil has 460 turns and self-inductance 7.50 mH. The current in the coil varies with time according to i=(680mA)cos[πt/(0.0250s)]. What is the maximum average flux through each turn of the coil? Homework Equations ##\varepsilon_{ind} = N \frac{d\Phi}{dt} ...
  38. Dante Meira

    Repulsion between permanent magnet and air core coil

    I formulated a statement about the repulsion between a permanent magnet and an air core coil (electromagnets without a ferromagnetic or ferrimagnetic core), and I believe this statement is true, but I would like to seek the opinion of others about it: "In a system where an electromagnet made...
  39. K

    How to wind a DC generator coil?

    I want to make a dc generator and not sure my design will work. I will wind the coil on a donut shape disk and put 6 rectangular magnets on a disk rotor with North Pole face the coil. Please see attached pictures. Will this design works or have problems? Can I have one continuous coil or I...
  40. Wrichik Basu

    Why are there three wires in secondary coil of transformer?

    This is a 12-0-12 transformer that I intend to use in my circuit: Why are there three wires in the secondary? One is of course the neutral (in black). Why are there two live wires? As an additional question, can I use four 1N5408 rectifier diodes to convert the output of this transformer to...
  41. B

    Transformer: single primary coil and multiple secondary coils

    If I have a coil with 10 turns and a primary voltage $$V_p$$ and primary current $$I_p$$ and a single secondary coil with 10 turns, I understand the power in the secondary will be $$P=V_pI_P$$ and hence voltage and current in the secondary coil will be the same. If I now bring a 3rd coil with...
  42. Krushnaraj Pandya

    Magnetic field due to spiral coil

    Homework Statement Consider a spiral of 20 turns with inner radius R and outer radius 2R. If the current is i, find magnetic field at the center of spiral Homework Equations From Biot-Savart law-dB=mu(idl)/4pi*x^2 The Attempt at a Solution Integration seems like a good option. x is...
  43. G

    B Coil B field strength with different diameters

    Hi, I have a quick question. Say I have two metal rods or tubes and I want to make an electromagnet, one rod is with a diameter x and the other rod has a diameter of x2 (two times larger) Now I take the same gauge copper wire and wrap an equal amount of turns around each of the two rods. Then I...
  44. MARX

    Kleppner Mechanics: Disk and coil spring

    Homework Statement A solid disk of mass M and radius R is on a vertical shaft. The shaft is attached to a coil spring that exerts a linear restoring torque of magnitude Cθ, where θ is the angle measured from the static equilibrium position and C is a constant. Neglect the mass of the shaft and...
  45. mheruian

    Winding Direction Consideration (Proper Winding)

    Hello, I'm boy who suddenly been strucked by curiosity on how hand crank generator works and i watch and read some of how to create one, specially this one on youtube: and i want to create one but i don't have a 3D printer, but i saw some alternative but as i do/design my own coil based on...
  46. A

    Why does a coil squash my function generator signal?

    Greetings, In the first picture below, I create a 5 volts sine amplitude signal with a frequency of about 100 Hertz. The 3 Ohm, 400 turn coil (that will eventually be part of a transformer) is not initially connected. The output waveform from my function generator completely matches my input...
  47. J

    How does a Ruhmkorf coil produce radio waves?

    Does the spark frequency = the interruptor frequency = radio signal frequency. From the sources I have found these frequencies don't seem to match. We use a 9V DC one at school. Many Thanks
  48. J

    Magnet moved in a circular coil

    Homework Statement Homework EquationsThe Attempt at a Solution As the magnet moves in and out of the coil , flux linked with the coil changes , as a result an EMF is induced in the coil . A current flows in the coil . The current depends on how fast the magnet is moved . Current will vary in...
  49. F

    EMF induced in a coil encircling an ideal solenoid

    Homework Statement A current I(t)= (0,160 A s^{-3}) t^3 flows through an ideal solenoid with a turns density n = 9,00 \cdot 10^{-3} m^{-1} and a cross sectional area A_s=2,00\cdot 10^{-4} m^2 A single loop of wire has the same axis as the solenoid, but its radius is larger. That is: the loop...
  50. Mohammad Hunter

    Electromagnetic coil and capacitors vs resistance

    I'm not really sure if this is even scientific but while calculating how much energy is stored in electromagnetic coils and capacitors, pretty much the same formula is used: For electromagnetic coils it's U=0.5LI2 For capacitors it's U=0.5CV2 Why I think they're the same is that in a sense L to...
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