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. J

    Loop Coil Comparison: Hollow Tubing vs. Solid Wire

    Is the same inductance formula valid for a coil made of hollow tubbing that for a solid wire made , with both having the same width?, and supposing that a high frequency current flows through it whats the skin effect influence on the result
  2. K

    Air cooled coil electromagnet ?

    Air cooled coil electromagnet ? Hi. I'm a (very) Junior researcher I'm trying to biuld a solenoid electromagnet (air bore, not metal), But I need it in a specific size and most important I have to have it AIR COOLED (by fan or compressed air). Does anybody know if such an electromagnet...
  3. J

    Soldering tap points onto a coil

    Hello All, I'm making a long coil for some experiments and I want to put some tap points onto the coil without actually cutting the wire. I was wondering if anyone knows of a simple way to do it? The coil is made out of insulated 22 gauge wire (regular not mag wire) wrapped on a core that...
  4. D

    Constructing a Competitive Alternative to the Tesla Coil: Tips and Tricks

    [SOLVED] pls HELP me There is an electronics competition, so can somebody tell me if there is something better than Tesla coil. The opposition is going to have a demonstration with a Tesla coil. What is your suggestion? What should I construct against the Tesla coil?
  5. S

    Self inductance of a solonoidal coil

    Homework Statement A long, solonoidal coil with 2000 turns produces a B field pf 3mT at its center when a current of 1A flows through the coil. If the cross sectional area of the coil is: 2*10^-3 m^-2, and the field is uniform throghout the solonoid, determine the self inductance of the oil...
  6. C

    How Does a Toroidal Coil's Magnetic Field Interact with a Bar Magnet?

    Say I've inserted a north pole of a bar magnet into a toroidal coil. When the bar is moving there will be an induced EMF in the coil which will lead to a magnetic field that opposes the initial magnetic field. From what I understand the B field in the toroidal coil is circular inside the coil. I...
  7. W

    One Photon from coil and battery

    I need only one photon from a coil and battery set up. Anyone know how I can get just one photon? e.g. 1) slowly increasing ramp voltage that spits out single photons slowly? 2) Send a tiny voltage in by pushing a switch? 3) Have many windings or just a few? Any clues...
  8. B

    How Does a Moving Coil in a Loudspeaker React to a Fluctuating Voltage?

    can anyone help with me understanding the physical mechanisms that determine the current that flows through a MOVING coil immersed in a magnetic field when a fluctuating voltage is applied across the coil? Also I need to find a Differential Equation that describes the behaviour of the current...
  9. M

    Maximizing Dipole Electromagnet Strength: Coiling Methods Compared

    I am designing an electromagnet and need a strong field strength. I have came across a few different ways to wire the coil and am curious which way produces the strongest dipole electromagnet. The coil is to be wound around a cylindrical steel core. The first way is what I think is the most...
  10. T

    Impedance of Coil - Why Does Impedance Increase?

    hi, I have tested impedance of transformer coil and I found out that if I would like to have smaller input impedance then I have to reduce the diameter of magnetic wire. I understand that If i reduce the cross setion of the wire then I will reduce the DC resistance. I don't understand...
  11. L

    Tungsten filament-finding length of coil

    Homework Statement Tungsten wire has an emissivity of 0.35. A tungsten filament in a light bulb can be considered to emit light only from the sides of the filament (consider it a cylinder... they are usually wire "cylinders" wrapped into coils.). If the operating temperature of the filament...
  12. D

    Calculating EMF from a Rotating Coil: Max & Avg Values

    On a particular dynamo, the rotating coil has 500 loops, each of area 2.5x10-4 m2. The magnetic field can assumed to uniform and of magnitude 0.400T. When the bicycle is ridden at a particular speed, the coil rotates with a frequency of 8Hz. What is the maximum emf produced? What is the average...
  13. Z

    What force acts against a magnet passing through a coil?

    A magnet will induce EMF when it passes through a conducting coil. Where does that energy come from? Does the coil do work on the magnet somehow? The B field induced in the coil should be parallel to the magnet's motion, so I would think it could not slow the magnet's progress. Does the magnet...
  14. M

    Transformer: secondary coil question

    Hi I wondered if anyone could explain as to how actually the whole process of transformation of voltage happens. I know the equations involved but can't get them together to reach a conclusion. When a.c. is passed throught the primary, a flux is induced in the core, which travels to the...
  15. K

    Square Coil, Round Hole and mutual inductance

    Homework Statement A square, single-turn wire coil L = 1.13 cm on a side is placed inside a solenoid that has a circular cross section of radius r = 2.77 cm, as shown in the figure below. Basically a big circle with a square in the center. The solenoid is 20.0 cm long...
  16. M

    Magnetic Flux (Induction - Magnet through a coil)

    Is the incoming flux (first peak) equal in magnitude to the outgoing (second peak) flux? Why? A magnet was dropped through a solenoid, this experiment was completed twice, a graph of Voltage (V) vs. Time (t) was made for each experiment. The area under each curve is defined to be equivalent to...
  17. K

    Find the maximum induced emf in the large coil solenoid

    Homework Statement Given: u_0 = 1.25664e-6 A 2 m long large coil with a radius of 14.6 cm and 320 turns surrounds a 4.2 m long solenoid with a radius of 4.6 cm and 7700 turns. The current in the solenoid changes as I = I_0 sin (2pi*f*t) where I_0= 30 A and f=60 Hz.Inside solenoid has...
  18. R

    Induced charge in coil from other static coils?

    Hello ALL, I have a question about magnetism and generating electricity in a coil from a group of another coils that are alternately switched on/off (cascade). Would a current be generated from a group of coils that are switched on and off in sequence, having another coil parallel to them...
  19. B

    Designing and Building a Tesla Coil: Tips and Experiences

    any of you every attempt to design and build a tesla coil. I would love to build one . Can any of you share your experiences when you first begin to construct the Tesla coil and how long did the project take? What materials do I need. Do you have to be an electrician to build a tesla coil
  20. S

    How to Calculate Induced Current in a Coil Outside a Solenoid?

    Homework Statement A coil of 120 turns and radius of1.8 cm and resistance of 5.3 ohm is placed outside a solenoid. If the current in the solenoid is changed, what current appears in the coil while the solenoid is being changed? Homework Equations emf= -dflux/dt = A*dB/dt emf=iR...
  21. K

    Music Musical Tesla Coil: Cooler Than The Electric Guitar

    Cooler than the electric guitar http://www.hauntedfrog.com/gt/movies/2007/duckon/SingingTeslaShow.html"
  22. G

    Galvanometer has a coil with a resistance

    part 1: A galvanometer has a coil with a resistance of 81 W. A current of 131 mA causes full scale deflection. Calculate the value of the series resistor that is required in order to use the galvanometer as a Voltmeter with 40 V full scale. so to make a voltmeter, the galvanometer and...
  23. M

    What exactly is the solenoid shape? Is it just the coil?

    What exactly is the solenoid shape? Is it just the shape of the coil with the core inside or do they refer to the shape of the magnetic field surrounding the coil?? Is this the solenoid, just the coil? Or are they talking about the magnetic field that surrounds the coil?
  24. M

    How does winding a metal wire into a coil create magnetic flux?

    I was reading there that if you wind a piece of metal wire into a coil it creates a magnetic field. Does this wire have to have current running through it? I know that a changing electric current creates a magnetic field but how does winding a piece of metal wire into a coil create magnetic flux?
  25. A

    A coil of wire is connected to an uncharged capacitor in a magnetic field

    a coil of wire is connected to an uncharged capacitor in a magnetic field... Homework Statement A 10-turn coil of wire having a diameter of 1.0 cm and a resistance of 0.20 ohms is in a 1.0 mT magnetic field with the coil oriented for maximum flux. The coil is connected to an uncharged 1.0...
  26. N

    Faradays law: magnetic coil question

    Homework Statement (The information is for several questions and i have posted one of them) Two coils magnetically coupled, Voltage of 240v, 50Hz applied to coil 1, current of 2A flows, second coil connected only to a high impedance rms voltmeter reading 100v find: The peak total flux...
  27. S

    Inductance coil with water pipe

    If I place a pipe filled with WATER inside of a coil and then half filled pipe of same material, does the inducatnec change? Will the change be able to be observed using multimeter? any ideas?
  28. D

    Magnetic Field at the Center of a Coil

    Homework Statement The radius of a single coil of wire is 0.22m. It carries a 200 A current that flows clockwise. A long, straight wire carrying a current of 310 A toward the right is located 0.05m from the edge of the coil. What is the value of the magnetic field at the center of the coil...
  29. R

    DC Motor: Rotating Coil in Magnetic Field

    The diagram shows a DC electric motor containing a rectangular coil of 20 turns and of length .50m and width .40m The coil is pivoted so that it can rotate freely on an axle. The coil is shown lying horizontally in a magnetic field of uniform stength .60T. A current of 3.5A is passing through...
  30. K

    Driving a coil Voltage drive? Current drive?

    Driving a coil...Voltage drive..? Current drive..? Hi Guys As the title...I am now having a 10 turns coil, does it really matter that I drive it with sinusoidal voltage signal or a sinusoidal current signal? Will it affect the response of the coil? (like resonance frequency, Q factor...etc)...
  31. K

    What Factors Affect the Average Induced EMF in a Rotating Coil?

    A circular conducting coil with radius 2.61 cm is placed in a uniform magnetic field of 0.827 T with the plane of the coil perpendicular to the magnetic field. The coil is rotated 180° about the axis in 0.222 s. (a) What is the average induced emf in the coil during this rotation? (b) If the...
  32. K

    What is the magnitude of the induced current in the coil

    The component of the external magnetic field along the central axis of a 50−turn coil of radius 5.0 cm increases from 0 to 1.0 T in 4.3 s. (a) If the resistance of the coil is 2.9 Ω, what is the magnitude of the induced current in the coil? (b) What is the direction of the current if the axial...
  33. S

    Current of a coil surrounding a solenoid

    A 40-turn, 4.0-cm-diameter coil with resistance R=.40 ohms surrounds a 3.0-cm-diameter solenoid. The solenoid is 20 cm long and has 200 turns. The 60 Hz current through the solenoid is I = I_0 * sin(2pi*f*t). What is I_0 if the maximum current in the coil is 0.20 A? Basically, there is a coil...
  34. M

    Helmholtz coil with a ferrous core

    Dear all, I know that I can create a uniform field using the design of a Helmholtz coil with an air-core. However, if I use a ferrous core like iron, will I still be able to create a uniform field under the same conditions? Also, how is the equation for the magnetic field, B, changed when...
  35. cepheid

    Magnetic Flux Through a Wire Coil

    Hi, This problem confused me the first time around, but I think I've got it. I just want a confirmation that my reasoning is correct. I know I have the correct answer, but what is important is the method of arriving at it. Homework Statement A wire is being wound around a rotating wooden...
  36. J

    Electric field for radially polarized coil

    Hello All, A while back, I created a document describing how one could create a radially polarized electromagnet (like a doughnut with the North pole in the center and the south pole on the outer edge) and I would like to know what the e-field would look like when the current is increasing in...
  37. M

    What is the principle of tesla coil'?

    What is the principle of "tesla coil'?? What is the principle of "tesla coil'? What is different between "tesla coil' and 'high-voltage transformer"? Thank you in advance!
  38. M

    How Can I Measure the Movement of a Loudspeaker Membrane?

    Hi, I'm kinda new her, so I hope this is the right place to post this. English is not my native language, so you might experience some spelling error:) I am working on a project that my teacher assigned med the other day, were I am supposed to find out how i can measure the movement/velocity...
  39. L

    Electromagnetism: Turning effect of coil

    Homework Statement This is a question about turning effect on a current-carrying coil lying between the poles of a magnet. Please refer to the following link: http://img11.picsplace.to/img.php?file=img10/22/N1_000.gif On the textbook, it is stated the turning effect on the coil can be...
  40. G

    Super Conducting Coil Properties

    I was wondering what the energy density of superconducting coil/tape is. I essentially what to be able to say is for every centimeter or inch of this material this is the amount of energy could be in it (kW, kWh, etc). So the background; I would like for the parameters to be for...
  41. L

    Radius of coil in magnetic field

    Homework Statement Two coils have the same number of circular turns and carry the same current. Each rotates in a magnetic field in a setup similar to the square coil in the figure below. Coil 1 has a radius of 4.2 cm and rotates in a 0.19 T field. Coil 2 rotates in a 0.42 T field. Each coil...
  42. J

    How Do You Calculate the Frequency for a 90 Degree Phase Shift in Coils?

    Hello All, I did an experiment recently involving two coils in series with a high frequency signal running through them. My goal was to determine at what frequency the signal in one coil would be phase shifted by 90 degrees with respect to the first coil. I was able to experimentally...
  43. J

    EMF canceling in toroidal coil setup

    Hello All, My question concerns induced emf in an air-core toroid setup. This is simply a thought experiment and I think I know the answer to this but thought I would run it past you all anyway. Picture a non-magnetic toroidal core with two one-layer coils wound on it 180 degrees apart...
  44. S

    Calculating EMF Induced by a Moving Wire in a Magnetic Field

    Can i get some help with this homework problem?? A physicist wraps a long copper wire around a toilet paper roll and places the roll in a uniform magnetic field. The axis of the roll is aligned with the field. The radius of the roll is r = 6 cm and the strength of the field is B = 0.1 T. If the...
  45. S

    Calculating Induced EMF in a Coil with Uniform Magnetic Field

    I have a homework problem where there is a long copper wire around a toilet paper roll that is placed in a uniform magnetic field. The axis of the roll is aligned with the field. I am given the radius of the roll, strength of the field, and a velocity at which the wire is unrolled. How do i...
  46. ?

    Currents and magnetic fields in a coil

    Please help me if you can... question: Use the following quantities to calculate the magnetic field strength of the horseshoe magnet. Mass of coil: 20 grams current in coil: 2.0 amps length of bottom of coil: 10cm angle coil makes with vertical: 30 degrees Hint: Equate magnetic...
  47. E

    Magnetic Flux and Induced EMF in a Coil

    In a physics laboratory experiment, a coil with 210 turns enclosing an area of 12.7 cm^2 is rotated during the time interval 3.70 \cdot 10^{−2} sfrom a position in which its plane is perpendicular to Earth's magnetic field to one in which its plane is parallel to the field. The magnitude of...
  48. F

    Electric Heating Coil: Potential Difference in 3.5 mins

    An electric heating coil is immersed in 4.2 kg of water at 22°C. The coil, which has a resistance of 260 Ω, warms the water to 33°C in 3.5 mins. What is the potential difference at which the coil operates? I was looking through the chapter, and did not see any equations that I can use that...
  49. J

    Wind Toroidal Cores - Tips for 20 Gauge Magnet Wire

    Hey Everyone, I recently got a hold of a coupe of toroidal cores that I want to wind some wire on (see pic). They are roughly 2.5" OD, 1" ID, 1" thk. I plan to wind two coils of 20 gauge magnet wire onto them but I was wondering if anyone here knows how the factory-made ones are wound? Do...
  50. J

    Calculating induced power in coil

    Hi, I'm working on making a coil and I was wondering if there are some nifty equations out there to predict how much power the coils can make under a changing magnetic field of X gauss. I am going to be using 1 inch of a 3/8" x 2.25" bolt to wind my coil onto and I will be exposing it to a...
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