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. 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 =...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. A

    Understanding Torque in a Metal Coil with Magnetic Field

    Homework Statement For a metal coil, if a magnetic field is being applied parallel to each circular loop, why is there torque being exerted on the coil? Homework Equations torque=(magnetic field)(area)(current) The Attempt at a Solution When I cross the current with the...
  7. L

    Calculating Magnetic Dipole Moment & Torque of Coil in Magnetic Field

    Homework Statement A circular coil having 20 turns and a radius of R = 12.8 cm carries a current of 2.70 A. It is placed in a uniform magnetic field of 60.0 mT. The initial angle between the magnetic moment of the coil μ and the magnetic field B is 26.0o. 1)Calculate the magnetic dipole...
  8. M

    Induction Coil Help - Output Voltage & Tesla Coil Use

    ok, i recently acquired a 25mm spark gap induction coil. the input voltage is 6v dc. how can i know what the output voltage is? also, i want to use this as a substitue in place of a nst to power a 6'' tesla coil. will it work? i mean the basic idea is ot the a high voltage input and the...
  9. J

    Moving a bar magnet through a coil

    Homework Statement You move a bar magnet through a coil at a constant speed. Graph the flux through the loop as a function of time. Graph the induced current in the loop as a function of time. Homework Equations The Attempt at a Solution Graph of flux vs time: I'm thinking is...
  10. S

    Primary coil of an ideal transformer. I need an equation.

    Homework Statement The primary coil of an ideal transformer is connected to a 120-V source and draws 1.0 A. The secondary coil has 600 turns and supplies an output current of 5.0 A to run an electrical device. A) What is the voltage across the secondary coil? B) How many turns are in the...
  11. W

    Relation of I and V in secondry coil of transformer?

    One of the function of transformer is to increase the Voltage and decrease the current,It is according to P=IV.The decrease in the current will produce the loss in energy from the resistance of supply lines i.e P=I^2.R. My question is that the P=(V^2)/R is also the power loss and in case of...
  12. C

    What Determines the Magnetic Field Orientation in a P Type Semiconductor Coil?

    P type semiconductor coil... The magnetic field orientation in a P type semiconductor wire, in which a DC current is flowing will be caused by the direction of movement of the electrons or the positive holes?
  13. jegues

    Transformer Induction coil (COIL CONSTRUCTION)

    Hello all, I'm currently working on a project and I have a question in regards to creating an efficient induction coil for our circuit. Without going into the specific details of the circuit(We aren't given the details anyways, just the circuit itself), it basically imitates a transformer...
  14. L

    Rotation Rate of a Generator Coil

    Homework Statement If the rotation rate of a generator coil is doubled, what happens to the peak emf? Homework Equations The Attempt at a Solution I think it stays the same. Am i right?
  15. M

    Where Does Lenz's Law Apply in an Automotive Setting?

    A bar magnet is dropped from rest through the centre of a coil of wire which is connected to a resistor and datalogger. The resistor and datalogger are to the left in the diagram, and the coil on the right side. Add an arrow to the wire to show the direction of the induced current as the...
  16. M

    Magnetic field of a rectangular coil

    I got this formula for the magnetic field of a square-shaped coil: B = m0*2*sqrt(2)*I*N/(a*pi), where m0 is the permeability, and a is the side of the square... I can't really get why it is so, and my best tries resulted in approximation of the 'diameter' of the coil, for example by taking the...
  17. F

    Does a potential coil carry current?

    I have seen the potential coil go across two phases to measure voltage. But there is no neutral attached to the potential coil. If the two lines were 120v ea. the potential coil will have 240v of potential going across it. How is it that this coil can measure the voltage in both...
  18. W

    10/1 step down tranformer, resistance, power loss of secondary coil

    Homework Statement A 10/1 stepdown tranformer has a full load secondary current of 50A and is rated 30kVA. The copper loss at full load is 280W. The primary winding has a resistance of 0.25ohms. The core losses are 120W. Find the resiatance of the secondary coil and the power loss in the...
  19. V

    Superconducting induction coil

    Looked at Maxwell's eqns after quite some time,and was wondering, what happens if we apply an alternating flux to a superconducting coil? An emf should be produced, but there's actually no emf in a superconductor!
  20. V

    What is the induced voltage in the tilted coil frame?

    Homework Statement As shown in this picture: a 18 cm long solenoid with 1500 loops (N = 1500) and radius 2 cm is located at the center of wire frame (coil) that is 5(width) by 8(height) cm. There is a current inside of solenoid that is growing from 0 to 2.5 A in 7.5 seconds that rotates...
  21. H

    Design a Helmholtz Coil: Step-by-Step Guide | Electronic Engineer

    Dear Sirs, I was asked to design a Helmholtz coil. Being an electronic engineer, I can design electronic circuits but I have no idea about designing Helmholtz coils. Can you help me by suggesting a paper or article that describes a straightforward, step-by-step method for designing these...
  22. Z

    Voltage Induced in Coil: Hall Effect

    Homework Statement http://img697.imageshack.us/img697/2317/img11l.jpg (a = 0.10 m and b = 0.16 m) i=3t^3 - 5t (i - ampéres t - seconds) Determine the voltage induced in the coil to the instant t = 3 sec. well as the current direction. Homework Equations Hall efect The...
  23. F

    Finding the inductance of a coil

    Homework Statement A circular coil has a radius 0.10 m and 30 turns. An external magnetic field 2.60 mT is perpendicular to the coil. a) If there is no current, find the magnetic flux in the coil. b) When current = 3.8 A in some direction, there is no more net flux in the coil. Find the...
  24. S

    What is the Inductance of the Coil in a Radio Tuning Circuit?

    Inductance of the coil?? Homework Statement A radio has a tuning circuit consisting of a variable capacitor and antenna coil. IF the circuit has a maximum current when C=300pF and f=40kHz, what's the inductance of the coil?? Homework Equations f= 1/(2pi root (LC)) The Attempt...
  25. B

    Concept question, coil spring and energy.

    Homework Statement A coil spring of mass m rests upright on a table. If you compress the spring by pressing down with your hand and then release it, can the spring actually leave the table? Explain, using the law of conservation of energy.
  26. B

    Electromagnet coil core to yoke ratio?

    I'm building pairs of coils with standard core heights and diameters and linking each pair with a yoke. The magnets all run at 6V DC with windings of 24 AWG magnet wire in 6/8/10 layers. Is there a ratio of coil core mass to yoke mass for maximum efficiency? (shown below)
  27. 2

    Need help with Dynamo rule applied to coil and magnet:

    Hi, (I posted this on TSR as well, but they're being a bit slow...) Take the following setup: If you move the bar magnet left and right (a few cm) inside the coils, so that the ends do not leave the coil, will it induce a current/emf? I presume it does so, as I have been taught. But I don't...
  28. W

    What is the function of a copper-coil electronic component?

    What is this(copper-coil one)?
  29. C

    What Determines the Direction of Induced Current in a Parallel Coil Setup?

    Homework Statement P and Q are two coils arranged in parallel to each other and coaxially. Q is connected in series with a cell, a closed switch S and a rheostat. Determine the direction of the current in P when: the switch S is opened. Homework Equations Lenz's Law: The direction of the...
  30. H

    Uniform Magnetic field in a circular coil

    A 138 turn circular coil has a diameter of 2.00 cm and resistance of 53.0 Ω. The plane of the coil is perpendicular to a uniform magnetic field of magnitude 1.00 T. The direction of the field is suddenly reversed. a.) Find the total charge that passes through the coil. b.) If the reversal...
  31. N

    Capacitor discharge through a coil, need to find current

    I'm designing a circuit to discharge a capacitor though a coil of wire to make a large magnetic field, which is basically an undriven RLC circuit which starts out with a charged capacitor in series with an inductor and a resistor (the coil having a certain resistance in addition to its...
  32. A

    Calculate voltage induced on a coil

    Hi, i m new here n very poor in EE.. just want to ask that, is there any formula for us to calculate voltage induced on a coil if we have the info like the number of turns of the coil n the flux (mWb/sec).. cos i can't get from google as well...sorry for trouble n thanks for ur guiding...
  33. H

    Flux Linking in secondary coil for Toroidal Transformer problem

    Homework Statement A toroidal transformer has been built. It has a square section 'doughnought' shaped non-magnetic core, inner radius 'a' and height 'h' around which the secondary transformer has been wound 'n' times. Calculate the flux linking the secondary due to a time dependent current...
  34. D

    Current In Coil Around A Capacitor

    1. Homework Statement See attachment. 2. Haven't gotten there yet. 3. The problem I'm having with this is seeing the connection between the capacitor (at least, that's what I assume that square thing is) and the loop. Frankly, I don't see why there would be or why there must be...
  35. K

    Induced EMF on a primary coil by a secondary coil

    [b]1. Derive an equation to find the induced EMF on an inner solenoid by a changing current on an outer solenoid. Homework Equations We're given the equation EoRMS=(No*Ai*(2*pi*f)*(permeability constant)*IiRMS)/Li for the induced EMF on the outer solenoid by a changing current in the...
  36. J

    What is the Average Induced EMF in a Rotating Coil?

    Homework Statement A rectangular coil of 200 turns has a length of 200 mm and width 120 mm. The coil rotates with a constant angular speed of 1200 revolutions per minute about an axis through the midpoints of its longer sides in a uniform magnetic field of 2.4 x 10-2 T. Starting from a...
  37. B

    How Does Changing Wire Resistance Affect EMF in an AC Generator?

    Homework Statement This is the solution to one of the problems I came across: In an AC generator, a coil spins in a magnetic field. Of the following choices, circle the one that will not cause an increase in the EMF generated in the coil? a. replacing the coil wire with one of lower...
  38. F

    Flux of magnetic moment into a coil

    Hi, I've an experiment in which I've some magnetic material place into a coil that's used as sensor. Say it's a cylindrical one for the sake of simplicity. I'm trying to evaluate the flux induced by the material into the coil so that I can optimize the coil parameters (size, position and...
  39. C

    Current through a coil in a magnetic field

    Question: A coil of 90 turns, of resistance 6 ohm and area 28 cm² moves from a uniform magnetic field of 0.02 Tesla to one of 0.42 Tesla in 3.0 second. What average current flows in the wire (in amp) ? Relevant equations: EMF= (Area * Rate of change of magnetic flux) * Number of turns...
  40. A

    Orientation of coil in electric generator: Important?

    Hi, I'm working with my granddad on a project to build a (simple!) electricity generating windmill. We're not trying to make the most efficient design possible, just a reasonably efficient design given the simple tools and materials we're using. It's mostly just a project for fun! :) So, we...
  41. O

    What are some ways to improve wireless energy transfer using coil antennas?

    I've found this video on the web: http://www.youtube.com/watch?v=TIhPayFBE9c&feature=related and id like to be able to build one myself. But i don't really know how to start with this nor how it works. -The 8 shaped coil is really 8 shaped or just 2 coils bound together? -how do you make...
  42. M

    Electromagnetic induction Coil testing

    Whats the easiest way to test the max output of electricity induced in an air coil. I will wire it 3 phase delta. (or double delta) Will I need a resistive load attached for current flow? What should I use? How do I test? Use a multi tester? Is there math I can use to estimate the amount. I...
  43. J

    ELECTROMAGNETISM-torque on a current coil

    A circular coil of 50 turns has a radius of 0.2m and carries a current of 5A. The coil is in a field where the magnetic induction is 0.6 Web/m^2. What is the max torque on the coil? I used the formula for the torque on a coil: r=NBIAcos(theta) I assume that the angle for max torque is 0 my...
  44. Q

    [HELP] Confused about EMF induced in rotating coil

    Ok, now I got another question while doing electromagnetic induction questions. I know flux linkage=NBA and in a rotating coil, Flux linkage=NBA cos wt, which differentiated (Faraday's Law) wrt time gives E=NBAw sin wt, where w = angular frequency. However, when the plane of the coil is...
  45. Q

    [HELP]Confusion on torque of rotating coil

    Hi everyone. I have a confusion over a certain concept. I know the torque for a rotating coil in a uniform magnetic field is BIAN. But what if the coil is at a certain degree to the magnetic field? http://img44.imageshack.us/img44/1926/magnetic.th.png Sorry for the bad drawing. My...
  46. D

    Emf induced in the windings of coil

    Homework Statement a tightly wound circular coil has 36.8 turns, each of radius .1m. the uniform magnetic field is in a direction perpendicular to the plane of the coil. the field increased linearly from 0 to .42t in a time of .251s. what is the emf induced in the windings of the coil...
  47. M

    Calculating Torque on a Circular Coil in a Magnetic Field

    Homework Statement a circular coil of wire has a diameter of 2 m and contains 10 loops. The current in each loop is 3 amps, and the coil is placed in a 2 tesla magnetic field. Determine the maximum torque exerted on the coil by the magnetic field. Homework Equations F = IL x B...
  48. M

    Calculate the current in the coil

    Homework Statement A circular coil of 394 turns and area 0.78 m2 is in a uniform magnetic field of 0.8 T. The maximum torque exerted on the coil by the field is 0.0059 N · m. Calculate the current in the coil. Answer in units of A Homework Equations torque= i*A*B The Attempt...
  49. B

    Force on a Permanent Magnet Falling through a Coil

    What is the drag force on a magnet falling through a coil? I have found several sources online describing the drag force on a magnet falling through a conductive pipe. How might this vary if a coil is used in place of a pipe? Does the coil need to be connected to a circuit to create this force?
  50. 0

    I am looking for the B-field of a real coil.

    I am looking for the B-field of a real coil. So a straight piece of pipe with some current density. Is it correct that there is no analytical solution to this? It would be enough if I had the field of a current rotating in a cylinder obviously. I am working on some Biot-Savart but either I...
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