What is Coils: Definition and 203 Discussions

An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. Some coils have an internal resistor, while others rely on a resistor wire or an external resistor to limit the current flowing into the coil from the car's 12-volt supply. The wire that goes from the ignition coil to the distributor and the high voltage wires that go from the distributor to each of the spark plugs are called spark plug wires or high tension leads. Originally, every ignition coil system required mechanical contact breaker points and a capacitor (condenser). More recent electronic ignition systems use a power transistor to provide pulses to the ignition coil. A modern passenger automobile may use one ignition coil for each engine cylinder (or pair of cylinders), eliminating fault-prone spark plug cables and a distributor to route the high voltage pulses.
Ignition systems are not required for diesel engines which rely on compression to ignite the fuel/air mixture.

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  1. S

    How do i calculate magnetic coils output volts ?

    i am planning to make a magnetic generator & i have a question : if i provide a disk with 12 numbers of neodymium (1x1”x1”cylinder) (n48) magnets around it , moving by motor clock wise at 1500 rpm , ( magnet specification: Br: 13.80- 14.20 KG, Hcb: > = 10.5 Koe, Hcj: > = 11 KOe ) the...
  2. 0

    Does Stacking Coils Create a "Cancellation Field"?

    Some basic curve integration leads me to the believe, that if you stack two coils into one another with opposite identical currents and windings, their outside field cancels while the inside field is identical to the configuration without the outer coil. Is this correct and does this...
  3. T

    Rogowski coils problem help

    Homework Statement When a wire carries an AC current with a known frequency you can use a Rogowski coil to determine the amplitude Imax of the current without disconnecting the wire to shunt the current in a meter. The Rogowski coil, shown in the figure, simply clips around the wire. It consists...
  4. T

    Measuring Currents with Rogowski Coils

    Homework Statement When a wire carries an AC current with a known frequency you can use a Rogowski coil to determine the amplitude Imax of the current without disconnecting the wire to shunt the current in a meter. The Rogowski coil, shown in the figure, simply clips around the wire. It...
  5. T

    Rogowski Coils - find amplitude of Emf

    Homework Statement When a wire carries an AC current with a known frequency you can use a Rogowski coil to determine the amplitude Imax of the current without disconnecting the wire to shunt the current in a meter. The Rogowski coil, shown in the figure, simply clips around the wire. It...
  6. P

    Question about two circular concentric coils

    Homework Statement Two circular coils are concentric and lie in the same plane. The inner coil contains 110 turns of wire, has a radius of 0.010 m, and carries a current of 5.6 A. The outer coil contains 190 turns and has a radius of 0.014 m. What must be the magnitude of the current in the...
  7. N

    Two coils, proving some equations

    Homework Statement Imagine there are two parallel current-carrying coils, radius R, perpendicular to and centered on the x-axis, with centers at 0.5D and -0.5D. Both carry a current I in the same direction (clockwise). We would like to adjust D so that the magnetic field created by the coils...
  8. C

    Calculate Turns in a Coil w/ Relectance 12000at/wb & mmf 1200 AT

    How many coils ?? A coil is wrapped around a magnetic core of Relectance 12000at/wb. if the mmf is 1200 AT the determined flux how many turns is the coil if 2A were flowing threw it ? thanks, cs
  9. C

    Most efficient wire gauge for induction coils

    I am trying to find out which combination of wire loop diameter and thickness produces the most current. The problem with thin wire is obviously that it has a lot of internal resistance, but it is easier to wind in more loops. Does anyone know for a fact if a certain gauge/thickness is the best...
  10. J

    Induced current through a resistor - with variable resistor and two coils

    Homework Statement The two solenoids in the figure are coaxial and fairly close to each other. While the resistance of the variable resistor in the left-hand solenoid is increased at a constant rate, the induced current through the resistor R will A - flow from a to b. B - flow from...
  11. S

    Calculating Magnetic Field with Helmholtz Coils

    Homework Statement The coils in a set of Helmholtz coils have 186 turns and a radius of 15.9 cm. The current is set at 2.2 A. Express your answers in units of "T" for Tesla. a) Calculate the magnetic field along the axis at the center of the two coils (x = 0). b) What is the magnetic...
  12. I

    Understanding Air-Core Coils and Magnetic Flux Lines

    1. an air-core coil consists of 10 layers, and each layer is 11cm long and has 400 turns. the average radius of the layers is 2.25 cm. the flux density within the coil can be closely approximated by using the formula: B=µIN/2r which of the following best describes this statement? 1) true...
  13. G

    How do Telephone Loading Coils Improve High-Frequency Transmission?

    how do they improve high-frequency transmission (and not low-frequency?) ? I'm a biologist... Thanks
  14. C

    Power consumption of pulse coils

    I'm trying to optimize pulse coils and determine power consumption. According to Ohm's law: P = V2/R where P=power / V=voltage / R=resistance Why isn't Ohm's law providing the same results as actual meter testing?? Testing coils with 1 "C" battery: 1.5 volts #1) 2.3 ohm coil...
  15. E

    Two coils mutual force (HELP)

    Homework Statement In a compact cicrcualr coil "A" (radius R= 25cm),formed by N=150 loops of wire, flows I=10A current. There's another compact circular coil "B" over "A"(radius r= 1.5 cm, loops n= 30) coaxial with "A" distant X ,in which i= 4A flows . in the same direction of "I" (look...
  16. E

    Coils mutual force exercise: help

    Homework Statement In a compact cicrcualr coil "A" (radius R= 25cm),formed by N=150 loops of wire, flows I=10A current. There's another compact circular coil "B" over "A"(radius r= 1.5 cm, loops n= 30) coaxial with "A" distant X ,in which i= 4A flows . in the same direction of "I" (look...
  17. M

    How does the number of coils affect the rotational speed of a DC motor?

    Hello guys, I am curious about the effects of increasing the number of coils on the armature of a DC electric motor. Say if I switch from a coil from 80 turns to one with 160 turns (made of the same material) would the rotational speed of my motor decrease for the same voltage? I had several...
  18. B

    Calculating the Radius of a Rotating Coil in a Magnetic Field

    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 5.5 cm and rotates in a 0.17 T field. Coil 2 rotates in a 0.42 T field. Each coil experiences the same...
  19. S

    Coils & Questions: Charging Batteries with Magnets

    Ok, you know those flashlights that you shake to charge the battery? I'm no physics major, but I get the basic idea. The magnet is passed through the coil, creating an electrical current. So here's my question: Imagine I changed the structure of the coil a bit. If I take a series of magnets...
  20. S

    Understanding Helmholtz Coils in CGS Units

    Working in CGS units... hence i don't know if my answer is right or wrong anymore... It doesn't 'look' right Homework Statement Two coils are placed at l and -l on the Z axis as in the figure. They both carry a current I in the same direction (anticlockwise). Both have a radius of a. (Setup...
  21. X

    What is the coils inductance?

    A coil has a resistance of 2.10 ohms. The potential difference across the coil is 11.6 V at an instant when the current through the coil is 5.00 A and is decreasing at a rate of 36.0 A/s. What is the coils inductance? I thought i could use the equation X=2pi fL to solve for L.. but i am...
  22. D

    Mutual Inductance and coupled coils

    Homework Statement For coupled coils in this arrangement (illustration attached), show L_{eq} = \frac{L_1 L_2 - M^2}{L_1 + L_2 - 2M} Homework Equations KVL (mesh analysis) The Attempt at a Solution As you can see, I get to a final answer - which is not exactly the same...
  23. J

    How to Calculate Magnetic Field Strength of Helmholtz Coils?

    I am currently working on a research project, and need an equation or method to find the magnetic field strength produced by any number of helmholtz coils, and not just on the central axis, but at any position in the space around them. Can anyone help me out? Thanks
  24. L

    Exploring the Reach of Tesla Coils - Electric Bolts & Safety

    I watched a home video about the Tesla coil and saw the electric bolts...i thought the guy was standing kinda close to this thing but never got struck. Is there a limit to how far away the bolts of electricity can go from the coil? They looked pretty random.
  25. A

    Series or parallel coils for equal resonance

    I have a 555 out put connected to a coil and i get the frequency i need. But now i need the 555 to power more coils. How should i connect the coils to keep the same frequency. In parallel or Series? The 555 will not directly power the coils. It will switch a Mosfet and that will provide the...
  26. 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...
  27. A

    Induction Coils and/or Hertz Experiment

    Hi everyone, Just a quick question that was bugging me... If i was asked to draw the voltage output vs time of an induction coil...would it be absolute value sine curve?? Secondly i absolutely don't understand how in Hertz experiment, what the sparks jumping across have anything to do...
  28. S

    How do I take the first and second derivatives of the Helmholtz Coils equation?

    Homework Statement How do I take the first and second derivatives of the helmholtz equation? The equation is as follows: Bx= ((uR^2NI)/2) * ( [1/((x+a)^2+R^2)^(3/2) ] + [1/((x+a)^2+R^2)^(3/2) ] ) heres what I have to prove First Derivative...
  29. A

    How do you build a home-made speaker using magnets, plastic, coils, etc.?

    Our teacher wants us to construct a speaker that can provide sound (that can be heard from anywhere within the classroom) when connected to wires that are hooked up to some sort of device. I'm unsure of where to start and where to get the supplies. Since we are on the magnetism course, I know...
  30. A

    What is the resistance of meter coils?

    Hi, Just had a bit of a heated discussion with a friend of mine about electricity meters and I decided to get some info from you chaps so I can promptly add some ammo to my argument next time we meet! The claim is that you will get a low resistance reading between phase and neutral meter...
  31. 6

    Inductance and Coils Homework Solution

    Homework Statement Coil 1 has L=25mH and N=100 turns. Coil 2 has L=40mH and N=200. The coils are rigidly positioned with respect to each other, and their mutual inductance is 3.0mH. A 6.0mA current in coil 1 is changing at 4.0 A/s. (a)What magnetic flux Phi12 links coil 1 to coil 2, and what...
  32. T

    Distance relationship between primary/secondary coils

    We have done a simple experiment on AC transformers. Given: AC Supply. Big primary coil. Smaller secondary coil. Even smaller metal rod. (They all fit into each other) Voltmeter What we did: Connected AC supply to the primary coil. Voltage kept constant at all times Secondary coil was placed...
  33. S

    Calculating EMF in Metal Detector Coils

    Can i get some help with this problem? This problem deals with the basic loop configuration you will use in the laboratory to construct a metal detector. Two concentric circular coils of wire lie in a plane. The larger coil has 49 turns and a radius of a = 7.90 cm. The smaller coil also has 49...
  34. L

    Calculating EMF from Coils in Rotating Magnetic Field

    To find the emf generated by two ten turn coils, the planes of which are at 60 degrees in a radial magnetic field B=Bcos(theta)sin(omega*t) in the direction Ar, that rotates with omega rad/sec at the instant when the coil A1A2 makes an angle alpha with the plane of the maximum flux density...
  35. E

    Mutual Inductance and wire coils

    Hi..I am new here and I am really thankful for any help that I may get :blushing: I am stuck in a problem of mutual inductance. It seems fairly simple, yet I cannot get the correct answer. Two coils are close to each other. The first coil carries a time-varying current given by I(t) =...
  36. J

    Identical Springs: Stretching 0.160m with 50 Coils

    An object is attached to the lower end of a 100-coil spring that is hanging from the ceiling. The spring stretches by 0.160 m. The spring is then cut into 2 identical springs of 50 coils each. Each spring is attached between the ceiling and the object. By how much does each spring stretch?
  37. J

    Understanding Oscillator Circuits: Effects of Adding a Second Coil at 90 Degrees

    Hello everyone, In my continuing pursuit of understanding of oscillator circuits, I came up with this question and was wondering if anyone here could give me some insight on this. I drew a picture to help me explain the idea but I would like to know what would happen if you have an inductor...
  38. J

    Creating a Self-Resonating Coil: Understanding Harmonic Frequencies | Jason O

    Hello, I am teaching myself about oscillator circuits and I was wondering if someone could help me understand if it is possible to make a coil that will resonate at a natural frequency. I was reading some articles about experiments Nicola Tesla performed and the document I read (don't...
  39. J

    Air core Coils vs. Metal core coils

    Hi, I have a quick question. I was just wondering which type of coil is best for inducing electricity. If I pass a magnet over one end of the coil, would a metal core help more current to be induced or would an air coil be better? Thanks, Jason O
  40. cepheid

    AC Coils in Relays: Is DC Required?

    *Sigh*. I'm embarrassed to ask this question because it seems like a silly question. But at the same time, if I don't ask, I don't know how else I'll find out the answer. I have some documentation for work that says, "The relays are 110 V AC coils..." Believe it or not, that snippet is all...
  41. A

    Help with understanding force between two current carrying coils

    Hi I am currently involved in building a linear motor which is based around the coil gun principle. I am having trouble understanding the equation for force used to desribe the coilgun's action. namely: Fx = I1*I2*dM/dX Fy = I1*I2*dM/dX Here we are considering two coils of wire...
  42. A

    Help with understanding equation for force Between two current carrying coils

    Hi I am currently involved in building a linear motor which is based around the coil gun principle. I am having trouble understanding the equation for force used to desribe the coilgun's action. namely: Fx = I1*I2*dM/dX Fy = I1*I2*dM/dX Here we are considering two coils of wire...
  43. I

    Unmatched voltages on a transformer's primary coils

    Ok. say you have a transformer hooked up to two AC generators. They each produce the same amount of voltages. For the primary coils on the transformer (the 2 generators..) one is coiled 100 turns and the other 10 turns...the result? Continuation of question... now assuming that this means...
  44. N

    Maximizing Torque: Comparing Square and Rectangular Coils in Magnetic Fields

    Hey, Any help will do: A square coil and a raectangular coil are each made from the same length of wire. Each contains a single turn. The long sides of the rectangle are twice as long as the short sides. Find the ratio t(tau) square/t rectangle of the maximum torques that these coils...
  45. C

    Spining Sphere magnet inside rim of coils how do u calculate voltage

    Can we please imagine that a sphere Neodymiun magnet with a diameter of one inch was suspended or leviated, reducing friction to none, then we put this magnet inside an acrylic tube that created a vacuum by pumping out all the air out allowing the sphere to spin at enormous velocity with very...
  46. R

    Mutual Inductance of the cylinder coils

    Two coils are wrapped around the same cylinder form. When the current in the first coil is decreasing at a rate of -.242A/s, the induced emf in the second coil has a magnitude of .00165 Volts. What is the mutual inductance? What I did: E_2 = -M(\frac{d_i_1}{d_t}) .00165/-.242 = -M...
  47. J

    Making Electric Coils & Schumann Resonance

    Hello, I have kind of an odd question here. I was wondering how to make an electric coil that will naturally resonate at a perticular frequency. I am a novice when it comes to the associated physics so I'm hopeing that someone can explain this to me. I also have another related question. I...
  48. J

    Make Electric Coils Resonate: A Beginner's Guide

    Hello, I have kind of an odd question here. I was wondering how to make an electric coil that will naturally resonate at a perticular frequency. I am a novice when it comes to electronics so I'm hopeing that someone can explain this to me. I also have another relate question. I heard...
  49. A

    Helmholtz coils and a Hall Effect probe

    hello, here is my second message.(and my English is still very bad) I don't understand these 3 little experiments(we need Helmholtz coils and a Hall Effect probe) I know I have to draw a graph for each situation but I can't interpret the difference between the theory and the experiment...
  50. L

    Two circular coils and magnetic fields

    I have been driving myself crazy trying to figure out this problem, for a while now. I just can't get the right answer. should the number of turns be multiplied or divided by the radius? Please help me out. Two circular coils, concentric and lying in the same plane, produce magnetic...
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