# Coil Definition and 58 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. ### Do concentric coils steal power from one another?

The amount of power generated by a coil in a changing magnetic field is determined by the area perpendicular to the field, the field strength, and how quickly those values change over time, and is multiplied by the number of loops in the coil. But that made me wonder what would happen if one...
2. ### 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...
3. ### 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...

Hej Guys, Did anyone see anywhere an equation to this? If nothing else then a loading time formula for solenoid would do. Thank you!
5. ### 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
6. ### 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...
7. ### 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...
8. ### Helmholtz synthesizer experiment

Hello all! Inspired by the Helmholtz synthesizer, I am experimenting with electromagnetic excitation and tuning forks. http://www.sites.hps.cam.ac.uk/whipple/explore/acoustics/hermanvonhelmholtz/helmholtzssynthesizer/ How can I determine the size and charge of an electromagnet in order to...
9. ### Calculate the induced EMF for angle α

I have a question in my book and it’s confusing me a bit. I tried to search online for similar solved problems but couldn’t succeed. So here it goes: Calculate the induced EMF in a conductor loop when the angle between \vec{A} ~ and~ \vec{B} ~is~ changed ~from ~{0 °}~ to ~{α °} in 1...
10. ### Magnetic field in the gap of a tapered torus

Homework Statement Consider a toroidal electromagnet filled with a magnetic material of large permeability µ. The torus contains a small vacuum gap of length h. Over most of its length the torus has a circular cross section of radius R, but towards the gap the torus is tapered on both of its...
11. ### Calculating flux with a magnet and a coil

Homework Statement [/B] Hey, I'm having some difficulties with my physics project and I hoped someone could help me out. We have to calculate the magnetic field, but first we need to know the flux. This is the setup we got: We have to let a magnet fall through a PVC tube. The tube has a coil...
12. ### Mutual Inductance of Coaxial Tube and Coil

In my lab we are working with a Coaxial coil and stainless steel tube, and are aiming to find the mutual Inductance. I've done some looking around and have easily found the Inductance of a Coaxial cable, and for that of Coaxial coils, but am having trouble with a combination of the two. The...
13. ### Flux through a Coil

Thank you for reading my post. I can understand why a change in magnetic flux through a conducting surface would induce an emf, but how does this work when inducing an emf through a coil? How does the flux through the empty space between the wires have an effect on the electrons in the wire...
14. ### Electromagnet with two cardboard pieces

Hello! Recently I was going through some old exams and upon encountering this problem (which seemed pretty easy) I got stuck. Exams at my university are composed of individual tasks, each having three subquestions with four plausible answers respectively. Solution sheet gives results only, so...
15. ### What force does the current carrying coil feel?

Homework Statement What direction does the force that the current carrying coil feel point to when a magnetic field is turned on? A magnetic field is turned on and points from bottom to top and passes through a current carrying coil that has current passing through it CCW. Here is a diagram...
16. ### Help with 3axis Helmholtz Coil

First of all, hello to all of you. My question is, I want to simulate 3-axis Helholtz Coil in Maxwell 3d. I made some models of it, but I am not sure I got all right - especially ration of coils in x-y-z and their current excitation. Second, i'd like to see H field, or B field plot if some of...
17. ### The rate of change in the magnetic field linkage in a coil

Hi, I would appreciate it if someone explains the difference between these two phases regarding a coil rotates in a uniform magnetic field. 1. The rate with which the coil intercepts the lines of magnetic field in the dynamo is maximum when the plane of the coil is parallel to the lines of the...
18. ### I Tangential force on a linear solenoid plunger

Hello, I know how a plunger in a pull solenoid is pulled to the center of the solenoid. What I am wondering is the following. Does the plunger experience a centering force towards the center of the coil? If the plunger is moved slightly off-axis from the center of a circular coil, will the...
19. ### Why does the speed of the magnet matter in a coil?

I am currently studying Faraday's law and electromagnets and in class we were told that if you had a coil and say a bar magnet was passed through it the faster the magnetic field was applied to the coil the greater the induced voltage or emf would be. I do not understand why the speed would...
20. ### Pipe or coil in generators

Hi, I understand you can induce an electrical current by passing a magnet through a copper pipe. If so, why do generators (and motors for that matter) use coils in stead? Do coils allow a stronger current or greater efficiency? Where can I go to find out the most energy-efficient design for a...
21. ### Number of turns vs. wire length affecting voltage in coil

When winding a coil around a magnetic core, if you wanted to tap the coil such that each half has the same AC voltage output, would you: A) wind each part at the same RPM for the same amount of time, to get the same number of turns for each, or B) wind the second part proportionally less, to...
22. ### Magnetic flux and how to manipulate it discussion anyone?

Good day all, I am looking to discuss how to manipulate the magnetic flux of a coil. I unfortunately lack the math skills to calculate what I actually need to build for my project. I have been coop up in my garage trying to physically solve the problem but I am running out of time and money for...
23. ### Self inductance of a superconductor

Hi. Superconductors can be made hover above or even below magnets. As far as I know, this can be interpreted as an extreme form of Lenz's law: Eddy currents on the surface of the superconductor create an opposing force that is able to cancel gravity since the currents aren't affected by...
24. ### Magnetic flux through a loop

Homework Statement Homework Equations Flux = DeltaB * Area The Attempt at a Solution : Since the magnetic fields are going in opposite directions through the loop, I assumed that they would have different signs, so I chose 2.0 T to be positive and 1.0 to be negative, so when calculating the...
25. ### Inductive charging: Emf induced in two coil loops

Homework Statement So I'm trying to figure out this problem: The base of our charging station is composed of a coil with N1 turns and area A1 connected to a 120 VAC, 60 Hz source. The device has a smaller coil with N2 turns and area A2, which when attached will fit completely inside the...
26. ### Calculate the magnetic flux density

Homework Statement The magnetic flux density in the vicinity of a large air-cored electromagnet is determined by measuring the induced flow of charge in a small coil as the current in the electromagnet is switched on -- see the diagram below. Calculate the magnetic flux density at the...
27. ### What charge circulates through the coil?

Homework Statement Describe and account for two constructional differences between a moving-coil galvanometer used to measure current and the ballistic form of the instrument. An electromagnet has plane-parallel pole faces. Give details of an experiment, using search coil and ballistic...
28. ### Magnetic Field of Current loop around the Core

Hello friends, I am trying to find how calculate the magnetic field created by current loop considering that there is a some geometry of material that can enhance the magnetic field. I thought it can be solved by multipling by permeability μ but realized that the iron core changes the picture of...
29. ### Solenoid Diagram

Homework Statement (http://imagemap-generator.dariodomi.de/uploads/160725_010743_e42ea59f2569dfbV.png [Broken]) Homework Equations No equations or anything. Just need a visual concept understanding (11U Physics) The Attempt at a Solution The solutions say that all compasses should point...
30. ### Magnetism in coils

This is a graph for a magnet falling through a coil, it shows the p.d induced in the coil (the induced emf) when the magnet enters and then shows the induced emf in the coil when the magnet leaves. My question is why does the p.d appear to change direction? (i.e why the positive and negative...
31. ### Distance variation dependency between coil and magnet

Hello! I'm wondering if there's a general dependency/connection/correlation/function for changes in distance between an electromagnet (coil with iron core) and a magnet (Samarium Cobalt). Here's a picture to explain what I mean: If I move the coil closer to the magnet (smaller x) the force...
32. ### Finding the current in a solenoid

Homework Statement A 40-turn, 4.0-cm-diameter coil with R = 0.40Ω 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 = Io sin (2Πft). What is Io if the maximum current in the coil is 0.20A? Homework Equations Ncoil =...
33. ### Magnetic field outside of a solenoid conceptual

How come the magnetic field outside a solenoid is practically zero? I've read reasons along the lines of: -The magnetic field cancels out on the outside. Of course the net force cancels out, but what if you have an object placed on just one spot? The force on that object clearly is not 0...
34. ### What is N of a solenoid?

i'm confused with N , it says that is the number of turns per meter , but is the meter the length of the wire or the coil height ?
35. ### Electrical energy converted to heat in coil

Homework Statement Given a coil with N turns, a radius of r, a resistance of R', and an induced current i'(t) running through the coil, determine the totale energy converted to heat in the coil for t>=0. EDIT: The circuit on figure 4 consists of a resistance R and a capacitor with...
36. ### Tension in a spring

Imagine a spring that has its two ends attached to a wall at the same height. The spring will adopt a kind of a ''U'' shape (maybe a parabollic shape would be more precise). Why are the coils near the wall more distant from each others than the coils at the middle of the spring ? I think it is...
37. ### Electromagnetics: Non-Symetrical coil with external iron

Hello, and thanks for looking at my question. For starters, this is NOT a homework question, or a question I will receive any credit for except maybe a "hey, cool". The level of difficulty is roughly a junior-year Electromagnetics class homework quesiton, I suppose? My Question is rather...
38. ### Is it possible to detect current ramp-up to DC with a coil?

Hi, I am thinking of ways to detect when an electrical device is turned on and off without actually touching or modifying the existing circuitry. More specifically, I have a hand held device powered by 2 x 9V batteries and with 2 electrodes connected through leads and plugs to sockets on the...
39. ### A coil moves into a magnetic field

Homework Statement A coil, made up of 1850 loops, is inserted in an electric circuit and has a resistance of 45,0Ω. The area of each loop is 4,70⋅10^(-4) m^(2). The coil moves from a region where there's no magnetic field, to a region where the magnetic field is present. The normal to the coil...
40. ### Wanted: Looking for a helmholtz coil in Brisbane, QLD AUS

Hi guys, I'm a typical nerd that wanted to do an at home science project but don't want to spend lots of money on this coil. I would love to borrow/rent one if someone could help me. Otherwise if someone new a cheap supplier that i could get one off? It looks like either of these pictures :)...
41. ### Coil winding direction

I am wrapping a transducer coil and had a question with the winding direction. Let's say that I am wrapping the wire around a bolt in a clockwise direction. After I reach the halfway point of the wire, if I then reversed the direction I am winding to counter-clockwise, what would it do? I am...
42. ### Inductance of wire loops

I found this formula to approximate the inductance of a coil of wire. But what if a solenoid were composed of N separate loops, where each loop of the solenoid is connected to its own battery? That is, what if the solenoid had the same number of loops and the same geometry, except that each loop...
43. ### Magnetic wheels....

I have a project I'm working on where I need to have a model train be able to have an electromagnet hold its wheels to the track -- so that it can go "upsides down" and resist derailment. I'm making the wheels and the track -- so all options are on the table. If I used a steel track (say...
44. ### Will a DC to Pulse Width Modulator work for SS Tesla Coil?

I am making a small solid state tesla coil. I have the secondary coil, toroid and primary coil but am not sure what to do for a control circuit. I was planning on using two 9 volt batteries for power. Would a DC to Pulse Width Modulator work? This is the one I was thinking of -...
45. ### Contactor Wiring Question

If I have a contactor that I want to use with two separate control sources, on a site with a single phase power source, is it possible to connect two 120V control signals to the contactor coil, potentially live at the same time and connected to the same source, without causing a short, or...
46. ### Formula for torque on a coil in a magnetic field

Hi! I have some simple questions on the formula for torque on a coil in a magnetic field, ie this one: τ = NIA sinθ where I is the current flowing through the coil, A is the area of one loop, N is the number of loops, B is the magnitude of the magnetic field and θ is the angle between the...
47. ### Tesla Coil Help

Hello all, I am in the process of building a tesla coil and I need a little help. I have everything completed enough that I can start testing it. I plug the coil in and the spark gap fires immediately and continuously, but no arcs come out the toroid. I tried moving the toroid closer to the...
48. ### Number of turns in coil to get an output of 8V

Hello! First of all excuse my English. I'm Swedish. I'm doing an exprement in which I utilize the energy from the rotation in a stroller wheel to charge a 5V battery . I plan to make a magnetic generator with a disc placed on a 10 " wheel, consisting of the 20 Neodymium magmeter on the radius...
49. ### Design a coil with a variable pitch but a constant length?

I believe what I am attempting to do is not possible but here goes. I want to design a fixed overall length coil which I can manually adjust the pitch on. Optimally one would be able to grab the coil and by twisting it in place would be able to change it's pitch by changing its diameter but not...
50. ### Size constraints of generators

Based on what I have gathered so far, I don't see why a micro-scale generator wouldn't work, but then again I am a geographer with modest calculus skills. My biggest problem is not knowing how much I don't know, and I am hoping some kind and wise soul on PF can cure my ignorance. Let's say I...