# What is Coils: Definition and 202 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. ### I Iron core barely boosting field strength

Hello, I am a chemistry intern currently running a project that involves both chemistry and electromagnetism. Bottom line, I'm a little out of my depth and have much to learn, and I'm having a bit of trouble with the coils I constructed. My setup will consist of four coils positioned...
2. ### Engineering Calculate the power of the coils in this RLC circuit

So my attempt was I1*jXl1+I2*jXm=I2*(jXl2-jXc2) + I1*jXm because they are parallel so they should have the same voltage. I got I1=-3*I2. I know that J=6-j4 and that J=I1+I2 so I just plugged in what I got and I ended up getting the result for I2 and I1. But they are not correct. Why? I am given...
3. ### Bidirectional current switching with single type transistor

So here is my dilemma. I have a test setup with multiple coils all lined up in parallel in such a way that one end of each coil is connected together while the other is connected to a switch (mosfet) the switches then connect each coil to ground but that ground can become + based on which coil...
4. ### I How Do Helmholtz Coils Affect Electromagnetic Beam Transmission?

What would the behavior of an electromagnetic beam (transmission) be if directed through a Helmhotz coil? Is there a different result with a 4 or 6 coil configuration (all orthogonal)? Is there a direct response depending of frequency of the EM transmission (10kHz - 10 GHz) and current being...
5. ### Discontinuous voltage graph for bullet going through metal coils

For this problem, The solution is, However, dose anybody please know why the graphs for ##V_1## and ##V_2## are discontinuous where they cross the time axis? Many thanks!
6. ### How to model "LITZ" or "STRANDED" coils and windings

In Simulation of transformer and electrical motors in software like ansys maxwell we usually have to model conductors, but does it matter how to draw them? I use Ansys software for finite element simulations. Maxwell, Simplorer, RMXpert and other toolboxes. but I always have a doubt on how to...
7. ### What causes knots and stress when untwisting ropes?

[Mentor Note -- thread moved from the schoolwork forums to GD as it seems like a more general question] Homework Statement:: Topoisomerases help in relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix (Topoisomerases are enzymes that...
8. ### How are coils arranged in a power station generator?

Hi, I wanted to know a couple of things regarding the construction of the stator and rotor of a generator in a power station. Firstly, how the copper windings inside the stator are arranged. I understand it’s a three phase winding where each phase has a set of two coils like this: Source...
9. ### 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...
10. ### Inductance of Parallel Coils on an uncut toroid magnetic core

Hi, I have a toroid of a soft magnetic material (any). I wind the complete toroid with single turn coils and connect all their terminals in parallel. Then I wind a second layer of single turn coils on the previous layer and so on. I want to calculate the equivalent inductance L. I calculate it...
11. ### Inductive Current Coupling Between Two Coils

In this case, we do not know any information about the current, right? Therefore, there is no matching answer.
12. ### Find maximum current in a coil using oscilloscopes and Faraday's Law?

The experiment consists of a large field coil (connected to a current source) surrounding a coplanar and coaxial small detector coil in the center of the field coil connected to the oscilloscope. 1. Matching Current v. Time Graphs to Oscilloscope Graphs Example of one pair of graphs (I'll...
13. ### Does Moving Coils in Electromagnets Create Current? Explained

A small coil is moved forward (without turning) between the poles of the electromagnet. Does an electric current develop in the coil? Explain the answer
14. ### Detecting coils inside steel cylinders

Just some idle Sunday musings. I have a steel pipe that is 2" ID, 2.5" OD, 10' long. I want to place a coil inside the pipe midpoint along the pipe and detect it's presence with a transmitter / receiver array. The array can consist of two coils wrapped around the outside of the pipe and can be...
15. ### Engineering Calculating Core & Currents for Coils and Cores

I can easily calculate the core and currents required for the coil and core, i get confused do the the external field, any help please.
16. ### Concentric coils for power generation

Most generators work by rotating a coil within a magnetic field. This induces a current in the coil and can be harnessed as electricity. I was wondering if it would be possible to generate more power by using more than one coil with each one being progressively larger wrapped around the others...
17. ### Correct statement about coils moving in and out of a magnetic field

Option B is correct. Using Lenz's law, the direction of current flowing in coil 1 is counter clockwise while in coil 2 is clockwise. Option A is correct. Using Fleming's left hand rule, the resultant magnetic force acting on the both coils is to the left. I am not sure about option C and D. I...
18. ### Find the EMF generated by a guitar string in the pickup coils

I tried using the general EMF equation but don't know how to apply it with the equation from the problem
19. ### Why don't electric motors use exciter coils like generators do?

I remember (long ago, in college physics) learning about electric motors and generators, specifically about the "exciter" coils in generators which did a better job than permanent magnets, because of a sort of "turbo" or force-multiplier effect. I notice, however, that while basically ALL...
20. ### How to optimize spark gap Tesla coils

My elementary school had its first annual science fair a few weeks ago, so me and my friend signed up and we decided to do it on wireless electricity. So naturally, we built a tesla coil. It took a couple of tries, but we eventually got it to barely illuminate a portion of a fluorescent light...
21. ### How to optimize spark gap Tesla coils?

My elementary school had its first annual science fair a few weeks ago, so me and my friend signed up and we decided to do it on wireless electricity. So naturally, we built a tesla coil. It took a couple of tries, but we eventually got it to barely illuminate a portion of a fluorescent light...
22. ### Mechanical loads on ITER's magnetic coils

Is there a prediction/paper/etc. about the mechanical loads that will be reacted onto ITER's magnetic coils? The reason I ask is a simple calculation. My understanding of the numerical figures on ITER are that it is intended to contain; density ~10^20 temperature ~20keV I think that means a...
23. ### Alternatives to creeping contacts for high frequencies

I anticipate immediately that I am not sure if this is the right place to ask my question, in case I had made a mistake I would migrate willingly into the relevant area. I have an RF circuit on small PCB board (about 3x2 cm) that moves along a vertical axis in a measuring probe (it serves...
24. ### Can I Just Change the Coil in Circuits to Find the Relationship Between B and r?

Homework Statement Homework Equations none The Attempt at a Solution I want to find the relationship between B and r. So, i have to change r. Do I just change the coil completely with a new one? I believe that this could greatly affect the set up and I don;t think it is practical. OR is...
25. ### Transformer: single primary coil and multiple secondary coils

If I have a coil with 10 turns and a primary voltage $$V_p$$ and primary current $$I_p$$ and a single secondary coil with 10 turns, I understand the power in the secondary will be $$P=V_pI_P$$ and hence voltage and current in the secondary coil will be the same. If I now bring a 3rd coil with...
26. ### Electromagnetic coil and capacitors vs resistance

I'm not really sure if this is even scientific but while calculating how much energy is stored in electromagnetic coils and capacitors, pretty much the same formula is used: For electromagnetic coils it's U=0.5LI2 For capacitors it's U=0.5CV2 Why I think they're the same is that in a sense L to...
27. ### Homemade electromagnet, considerations - strength

I'm making a solenoid electromagnet for gcse demonstration purposes and I'm trying to get a strong:muscle:, clear magnetic effect. I'v wrapped about 100 turns of enamel plated copper wire around a 4" bolt and also a 4" ferrite rod, and am applying 9v DC from a pp3 battery cell. In both cases...
28. ### Why no induced current when these coils are stationary?

These is there no induced current when the coils are stationary relative to each other? Isn't there still current (moving charges) in the the one on the left to cause a current in the one on the right when neither coil is moving?
29. ### Magnetic Field due to Opposing Coils

Homework Statement Describe the magnetic field you would observe if two coils were connected with magnetic fields pointing in opposite directions. Homework Equations No equation The Attempt at a Solution If the magnetic field was pointing in opposite directions, would it mean that it would...
30. ### Calculating B:I for Helmholtz coils

Homework Statement I've completed an experiment where the dependence of magnetic field strength ##B## on current ##I## is measured at the midpoint along the axis between two Helmholtz coils (separation distance = coil radius ##r##). I got the expected linear relationship from the data but am...
31. ### Adding a 2nd Secondary coil & effects

Hi, We have an induction heater, like a stove top one, not industrial. I want to understand what happens when an additional load is added that it isn't intended to receive. A plate goes on the induction warmer, it gets heated up, then removed and another plate takes it place. What happens if the...
32. ### Inductance in FEMM 4.2, series/parallel connection of coils

Dear Forumers, I have an axisymetric magnetics problem in FEMM 4.2. I'm analyzing a loudspeaker motor (permanent magnet included) with many coils. I would like to get the inductance for the coils connected in series and in parallel. Let's say that I have 2 coils, coil A (n=N1) and B (n=N2)...
33. ### What's the purpose of this dual coil?

What's the purpose of this dual coil? It has a blue and red cable. It stood alone, mounted (isolated) on the chassis of a PC PSU. It's in good condition, so I'm keeping it, but what can be achieved with it?
34. ### Mutual Inductance of two coaxial coils

Homework Statement Two coils of the same length and almost the same cross-section are put one inside the other. Find their mutual inductance if the self-inductances are and . Homework Equations 1) \phi_i=L_i I_i 2) \phi=\iint_A \vec{B} \cdot d\vec{A} 3) \phi_1=M_{12} I_2 The Attempt at...
35. ### One coil twisted in a figure 8 vs. two coils side-by-side

The side by side coils are round or oval, and wired together in series. Let's say the side by side coils are wound opposite (one clockwise and one counterclockwise) to match the direction of travel of the twisted coil's loops. Each of the side by side coils has the same number of turns as the...
36. ### Absolute Value of Magnetization

Hello, I'm a student of electrical engineering. This task appeared in one of the past exams. I've been using the procedure I believe should yield the correct result, however, it turns out I was wrong. Could somebody please check out where the mistake lays in my calculations? Homework Statement...
37. ### How are Superconducting Coils charged?

Superconductors can be used to store energy in the form of magnetic fields, because the current in a superconductor can persist indefinitely. In fact, some large power grids are already using this as a way to regulate power flow in the grid. My question is how are the coils "charged"? How do we...
38. ### How to find magnetic field in a square coil next to an RC circuit

Homework Statement 1. (35 pts) You have a coop job helping to test a capacitor energy storage system. There is a rather large capacitor with capacitance, C = 2.02F. It is charged to a potential V = 602.V with the polarity of the capacitor as shown. The large, solid line on the right of the R–C...
39. ### Need help shrinking turbine generator coils?

Hey everyone, New to the site and I'm liking what I've come across so far but I'm having some trouble with a project of mine. I'm an ME by trade but this is definitely more of an electrical engineering problem. I need to make a small turbine generator that operates in a water wheel type design...
40. ### One more question on Tesla coils :)

Dear Forum, I have recently tried to understand how a Tesla coil works. A Tesla coil seems very similar to a regular transformer. Based on my understanding, a transformer is fundamentally composed of two inductors (with possibly a different number of windings) interlinked by an iron core. A...
41. ### Concentric Coils EMF from Graph

Homework Statement Two concentric circular coils of wire lie in a plane. The larger coil has 61 turns and a radius of a = 7.40 cm. The smaller coil has 58 turns and a radius of b = 0.95 cm. The current in the larger coil has a time dependence as shown in the figure. Picture and graph...
42. ### Coils arrangement so the hotplate operates at 3 diff. powers

Homework Statement A certain electric hotplate, designed to operate on a 250 V supply, has two coils of nichrome wire of resistivity 9.8 * 10-7 Ω m. Each coil consists of 16 m of wire of cross-sectional area 0.20 mm2. (a) For one of the coils calculate (i) its resistance, (ii) the power...
43. ### Calculating Magnetic Field of Two Coils on a Common Axis

Homework Statement Two thin coils of radius R = 3 cm are d = 13 cm apart and concentric with a common axis. Both coils contain 10 turns of wire with a conventional current of I = 3 amperes that runs counter-clockwise as viewed from the right side (see the figure). (a) What is the magnitude...
44. ### Induction: Questions reg. Coils vs Parallel Conductors

Needing a bit of help here. I am trying to transfer an AC signal to a straight conductor via induction. I am trying to quantify the difference in amount of transferred signal (amps) when the source of the signal is a small coil versus a parallel running straight conductor. I am thinking its...
45. ### Magnets and coils configuration for electricity generation

My dad is working on a project where he intends to convert mechanical into electrical energy, and he was wondering if a particular magnet and coil configuration works for electricity generation. And if it does, how are the voltage and current calculated. Lets say: The coils have a diameter of...
46. ### Effect of number of coils on current in a generator?

Hello everyone and thank you for your replies in advance. I am currently doing a physics project where I am testing to see how the number of coils of wire effects the current generated when a magnet is run through the coil. I am currently just dropping the magnet through the coil from a constant...
47. ### Magnetism in Coils: Why PD Changes Direction?

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...
48. ### Electromagnetic induction question, coils and magnets

Say you have a coil connected in a closed circuit. You then move a magnet inside of the coil and it remains stationary inside of the coil. Is the magnet, even though it is stationary, still inducing an emf in the coil or is it not? I'm guessing it doesn't induce an emf in the coil because...
49. ### Some questions on transformers, coils, and short circuits.

Hi, I'm trying to wire a transformer which steps my mains voltage (240VAC) down. I just finished wiring the the primary to the plug, and thought I should test my connections by plugging it in. The coil was not inside the core or near the secondary, it was just lying on a piece of paper. I...
50. ### Engineering Short Circuiting 1 of 3 coils that are Wye connected

For this question I'm focusing on part B 1. Homework Statement Three similar coils, connected in star, take a total power of 1.5 kW, at a power factor of 0.2, from a three-phase, 415 V, 60 Hz supply. Calculate: a) the resistance and inductance of each coil; b) the line currents if one of...