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

    Induced emf in secondary coil - help

    induced emf in secondary coil - help ASAP Please Homework Statement A very long, straight solenoid with a cross-sectional area of 6.00 cm2 is wound with 40.0 turns of wire per centimeter, and the windings carry a current of 0.250 A. A secondary winding of 2.00 turns encircles the solenoid...
  2. J

    Magnetic flux through smaller coil within solenoid

    Homework Statement A solenoid has 235 turns of wire wrapped along its length of 27 cm. The diameter of the solenoid is 1.5 cm. In the middle of the solenoid is a smaller coil of diameter 1.0 cm with 50 turns of wire along its 2.0 cm length. The two coils are coaxial. A current of 15 A is in...
  3. L

    Calculating Magnetic Field of a Tight Coil

    Homework Statement A 1.88 m long wire carrying 3.1 A is wound into a tight, loop shaped coil 0.05 cm in diameter. What is the magnetic field at its center? Homework Equations The Attempt at a Solution I use Ampere's law but i get the wrong answer. I think i did not set up the...
  4. T

    Force on a Magnetic Dipole Around a Coil

    First of all, this is not homework (before anyone suspects). I'm just doing this out of hobby and expanding my education. I've been trying to come up with distilled expressions for force on a magnetic dipole , anywhere in space around a simple coil. I started out with these expressions...
  5. G

    Magnetic feild in circular coil

    Homework Statement A 20 turn circular coil of length 5.9 cm produces a magnetic field of magnitude 1.9 mT at its center. Find the current in the loop Homework Equations B=(moconstant)nI where n is the number of turns per unit length and I is current. magnetic field is B The...
  6. R

    How to not short circuiting an induction heating coil

    how to not short circuit an induction heating coil Just wondering about induction heating coils and how to not short circuit one. basically, if i hook up one end of the coil to the positive and one end to the negative (DC) i assume that i will be short circuiting the connection and also...
  7. J

    How Does Magnetic Field Orientation Affect Torque on a Solenoid?

    Torque on a soleniod / coil in magnetic field Homework Statement A solenoid having 180 turns and a cross-sectional area of 6.68 cm2 carries a current of 1.12 A 1) If it is placed in a uniform 1.12 T magnetic field, find the torque this field exerts on the solenoid if its axis is...
  8. C

    Finding the diameter of a coil.

    Homework Statement You have a 1.2-m-long copper wire. You want to make an N-turn current loop that generates a 0.60 mT magnetic field at the center when the current is 1.5 A. You must use the entire wire.Homework Equations What will be the diameter of your coil? The Attempt at a Solution...
  9. R

    Benefits of induction coil over an alternator?

    I'm just wondering about what benefits there are to building / using an induction coil as opposed to other devices to create devices for spark gap experiments. I am referring to the induction coils with a primary winding and secondary windings with enormous numbers of turns - similar to...
  10. S

    Help with Coil Winding for Water Fuel Cell Circuit

    I am trying to gather some info about winding inductors. This is not simple. I am trying to put together a resonant circuit to power a water fuel cell. I know a lot of people will say that this is bull but I don't care , I am having fun with it and am learning a heap. The circuit uses a bifilar...
  11. M

    Collapsing fields and coil polarity, freewheel diode, .

    When a DC coil (relay) is denergized, shouldn't the collapsing field cause a current that would oppose the change in current? Wouldn't that induced current be in the same direction as when the coil was enegized? Not seeing how a freewheeling doide gets forward biased. If I apply Lenz Law...
  12. F

    Calculating Current Draw in Electromagnetic Coil

    My situation is this. I have 6,560 ft (4 lb) of polyurethane-nylon coated #27 gauge round wire wound in a coil with an air core of 1 1/8 in. wide x 4 in. long x 4 in deep. I don't want to destroy my precious electromagnet so I'm afraid to give it some current. What would happen if I attached a...
  13. R

    Induced secondary coil flux field?

    Using a PMs' field and inducing a primary coil which is coupled with an independent coil of equal configuration to the primary. Would this secondary flux field be opposite and of equal EMForce? If so, Equal to the PMs' strength or the primarys' EMForce? Thanks Robin07
  14. H

    What is the optimal coil value for a toroidal coil used in a hydrogen generator?

    Hey fellas, I blundered onto this forum trying to figure out the value of a coil. I'm building a hydrogen generator and the plans call out for hand winding a toroid coil. I'd like to buy one instead but it doesn't give the value of the finished coil, just how to make it. It tells you to use...
  15. L

    A rotating coil measuring the magnetic field

    Homework Statement A rotating coil is a common device for measuring magnetic fields. Consider a coil of area A and N turns that is rotated at angular frequency w in a magnetic field. The position of the coil is adjusted so as to produce a maximum induced current Imax which can be measured by...
  16. D

    What Direction Does the Coil Rotate in a Magnetic Field?

    Homework Statement A circular coil, with radius of 10 cm, and 25 turns, rotates in a constant magnetic field of strength 2.4 T, with the axis of rotation perpendicular to the direction of the magnetic field. (a question about finding the induced voltage- 5.92 V) part C. If the...
  17. P

    How Is the Magnetic Field Calculated at the Midpoint of a Helmholtz Coil?

    Homework Statement The picture shows (there's supposed to be a pic) a Helmholtz coil consisting of two circular coaxial coils, each of 200 turns and radius R = 25.0 cm, separated by a distance s = R. The two coils carry equal currents i = 12.2 mA in the same direction. Find the magnitude...
  18. E

    Measure High Voltage using Coil Inductor

    Hi everybody, I need to indirectly measure the high voltage across a wire, which is one of the leads to a spark gap. I ran the wire through a coil inductor(air core) and measured the voltage across the coil leads with an oscilloscope when i get the spark. I also connected a resistor in series...
  19. S

    Simple harmonic motion of coil spring

    hi i ned a little help with this problem please. An object is connectedto a 100 coil spring, that is hanging from the ceiling. The spring stretches by 0,160m. What is the spring constant? Im not sure how to go about with this...is the force 100? please help. Thanks
  20. M

    Solving for Current in a Coil: A Troubleshooting Guide

    Homework Statement A 21.8 cm diameter coil consists of 18 turns of circular copper wire 1.70 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate of 8.15E-3 T/s. Determine the current in the loop. Homework Equations V=IR V=B/T * A * N...
  21. P

    Understanding Induced Voltage: Circular Coil & Permanent Magnet

    Homework Statement The sketches below show a circular coil and a permanent magnet; the arrows indicate both the magnitude and the direction of the velocities of the magnet and coil. In which situations will the induced voltage (and hence the current) in the loop be zero? (Enter your answer...
  22. P

    Induced emf in a Rectangular Coil

    Homework Statement A rectangular coil of 150 turns has dimensions of 23 x 70 cm and is located in a uniform 3 T magnetic field. In 1.2 s, the plane of the coil is rotated from a position where it makes an angle of 15° with the magnetic field to a position where it makes an angle of 72°...
  23. P

    Magnetic Field of 60-Turn Coil w/ 0.2m Radius & 4A Current

    What is the magnetic field at the center of a 60-turn coil carrying a current of 4 A, if it has a radius of 0.2 m? I was thinking of using the equation B=(mu0)(N/l)(current) But I was wondering do I use the radius for l or do I use the diameter?
  24. P

    What is the Maximum Torque on a Flat Coil in a Magnetic Field?

    Homework Statement A narrow flat coil wound on a square frame has 160 turns and sides of 34.0 cm. It carries a current of 5.30 A and is positioned in a 0.260- T magnetic field. What is the maximum torque that can be exerted by the field on the coil? Homework Equations Torque = (Number...
  25. clope023

    Changing Potential Energy of a Magnetic Coil

    Homework Statement A coil with magnetic moment 1.40 Am^2 is oriented initially with its magnetic moment antiparallel to a uniform magnetic field of magnitude 0.830 T. What is the change in potential energy of the coil when it is rotated 180 degrees, so that its magnetic moment is parallel...
  26. R

    Force produced by current carrying coil to move sludge(steel rod)

    hi everyone, I have a problem, if U see the photo I have coil which carries current of rectified ac waveform through it. I have sludge(Steel rod of weight 20#) which has to be moved till the centre of the coil. If the current in coil induces magnetic field to sludge to move upward, then...
  27. Cyrus

    What Are the Differences Between Magneto and Ignition Coil Systems in Vehicles?

    Im trying to find out the difference. It seems that an ignition coil converts the cars battery voltage from 12V to several thousand volts; whereas, a magneto creates several thousand volts without any input from the aircrafts battery.
  28. M

    Van der graaf generator and tesla coil

    Hello peoples. Im attempting to build a van der graaf generator and a small tesla coil. Hopefully I have come to the right place for help. Firstly I'll start with van der graaf generator. I am going to use pvc lower roller (negative charge) and nylon upper roller (positive). any suggestions...
  29. A

    Explain how an e.m.f. is induced in the secondary coil

    Homework Statement The photograph shows a transformer which has been cut in half. The transformer consists of primary and secondary coils wound around the same laminated iron core. The diagram shows a cross-section of the iron core and the two coils. One coil consists of a few turns of thick...
  30. T

    A Multirange Coil Ammeter Galvonmeter (?) resistance question

    [SOLVED] A Multirange Coil Ammeter Galvonmeter (?) resistance question Homework Statement A Multirange Ammeter. The resistance of the moving coil of the galvanometer G in the figure (See Below) is 48 Ohms, and the galvanometer deflects full scale with a current of 0.0200 A. When the meter...
  31. E

    Are 4uF Capacitors a Viable Option for MMC in Tesla Coils?

    MMC for Tesla coil, inquery... Hello all, Every project of mine starts like this... I first need to consider my budget. So, I am wanting to build a Tesla coil. I can get everything needed for this, but I have concerns about the primary capacitor. As I have looked all about the internet...
  32. H

    Magnetic flux in a coil, find current

    Homework Statement 1.) Problem (exam question that I got wrong and want to figure it out) A circluar coil of radius a=.35m rotates at a frequency of 120 hz in a constant magnetic filed of B=.8T. The axis of rotation is perpendicular to the field the coil has N =340 turns it has a resistance...
  33. B

    I'm thinking of building a Tesla Coil

    I have a very limited budget right now. How much do you think it would cost to build a small Tesla Coil? This would include buying the components of a Tesla coil.
  34. S

    A coil with turns given magnetic field, time find the emf induced in the coil

    A coil with 240 turns enclosing an area of 13.7 cm^2 is rotated in a time interval of 3.70×10^-2 s from a position where its plane is perpendicular to the Earth's magnetic field to one where its plane is parallel to the field. The Earth's magnetic field at the lab location is 5.9×10−5 T ...
  35. S

    EM: Magnetic induction at a point due to a line of current, or square coil.

    Hi everyone, (nb: I posted this in the introductory physics section, but maybe it should be here? I'm not exactly sure how to divide physics into introductory and advanced. I hope this isn't against the rules - it's only my second post!) I am trying to understand my EM course again, and I...
  36. S

    Find I(coil): Solenoid & Coil Setup

    Homework Statement A 44.0 -turn, 3.90-cm-diameter coil with R(resistance) = 0.510 surrounds a 2.40-cm-diameter solenoid. The solenoid is 16.0 long and has 240 turns. The 60 Hz current through the solenoid is I(solenoid)= 0.530Asin2\pift. Homework Equations Find the value of I(coil)...
  37. R

    Average Current Through A Coil Over An Interval

    [SOLVED] Average Current Through A Coil Over An Interval Homework Statement The problem comes from a homework assignment I have. It has to deal with average current flowing through a wire over an interval. It is stated as follows: A five-turn circular coil of radius 15cm is oriented with its...
  38. B

    What Formula Calculates Inductance for Jumble Wound Air Coils?

    I have noticed there are different Inductance formula's for a various types of air coils & there design, single layer spiral, flat wound spiral, multilayer etc. My question is for the design of Jumble wound --- Random wound air core coils: What is the Inductance formula for a Jumble...
  39. C

    What voltage appears across the primary coil of this transormer

    Homework Statement A step down transformer produces a voltage of 6.0 V across the secondary coil when the voltage across the primary coil is 120 V. What voltage appears across the primary coil of this transormer if 120 V is applied to the secondary coil? Homework...
  40. T

    How Does the Changing Current in a Solenoid Affect a Coil Within It?

    [SOLVED] EMF problem - Current in Coil Homework Statement A small square coil is located inside an ideal solenoid at the center with its plane oriented perpendicular to the axis of the solenoid. The resistance of this coil is 2.00 \Omega and each side is 4.00 cm long. The solenoid has 125...
  41. O

    Rectangular coil current problem

    please, i want to be sure of my password and user name can it be posted to email? also, idon't know how to submit questions can the guide lines be posted as well? Thank you. A rectangular coil, carrying a current of 400pie amperes, lies in the z=0 plane with its corners at the points...
  42. T

    How Close Is the Magnetic Flux Through a Coil to the Calculated Values?

    Homework Statement A long straight wire on the z-axis carries a current of 3.0 A in the positive direction. A circular loop in the xy-plane, of radius 10 cm, carries a 5.0-A current, as shown. Point P, at the center of the loop, is 25 cm from the z-axis. A circular coil of four turns, 2 cm...
  43. C

    Effect of Changing Magnetic Field on Flux through a Coil

    Homework Statement You hold a wire coil perpendicular to a magnetic field B. If the magnitude of B increases while its direction remains unchanged, how will the magnetic flux through the coil change? Check all that apply: The flux is unchanged because the position of the coil with...
  44. F

    Effects of Resistance & Speed on Coil Pendulum Motion in Magnetic Field

    How do resistance and speed of a coil in pendulum motion in a magnetic filed affect the induced voltage and the decay of Potential Difference? Details: Q1 When the speed of a coil is kept constant and a 3.3ohm resistor is added to the circuit of which the coil is a part of, the induced...
  45. F

    How Many Turns of Wire Does the Coil Have?

    Homework Statement A bar magnet with magnetic dipole moment 0.51 A m^2 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 magnet and the compass is a coil of wire of radius 1.5 cm, connected...
  46. K

    What is the theoretical limit to coil inductance over coil resistance?

    Is there a theoretical limit to the time constant of an electric motor? I was think, if inductance is simply the conversion of current into the magnetic field, and if increase in resistance limits that current for a given power supply, that having a higher time constant would in effect allow...
  47. Y

    Mechanical equivalent of a coil

    Hi. This is a simple one (I think): We all know a swing, or simple mass on a spring, moves in harmonic motion, and has a specific resonative frequency. We also know that the RCL circuit (which includes a coil and a capacitor) reacts similarly to an external oscillator, also with a specific...
  48. R

    Archived Current of Coil, and Emf of Coil.

    Homework Statement A magnetic field is perpendicular to the plane of a single-turn circular coil. The magnitude of the field is changing, so that an emf of 0.91 V and a current of 3.2 A are induced in the coil. The wire is the re-formed into a single-turn square coil, which is used in the...
  49. D

    Induction of a coil and force exerted on magnet in a magnetic field

    Hi! This is my first post on this forum, and I have two questions. First of all I'd like to mentoin that my math knowledge is at high school level + some basic calculus. Ah, and I haven't learned about (partial) differential equations yet. My physics skills go only as far as electromagnetism...
  50. B

    Calculating Number of Loops in Coil 2

    Homework Statement In each of two coils the rate of change of the magnetic flux in a single loop is the same. The emf induced in coil 1, which has 200 loops, is 2.67 V. The emf induced in coil 2 is 3.78 V. How many loops does coil 2 have? Homework Equations E=-N(delta Phi/delta t)...
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