What is Solenoid: Definition and 743 Discussions

A solenoid (, from the Greek σωληνοειδής sōlēnoeidḗs, "pipe-shaped") is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it. The term solenoid was coined in 1823 by André-Marie Ampère to designate a helical coil.In the study of electromagnetism, a solenoid is a coil whose length is substantially greater than its diameter. The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape.
In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. In simple terms, a solenoid converts electrical energy into mechanical work. The term is also often used to refer to a solenoid valve, an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid or linear solenoid. Solenoid bolts, a type of electromechanical locking mechanism, also exist. In electromagnetic technology, a solenoid is an actuator assembly with a sliding ferromagnetic plunger inside the coil. Without power, the plunger extends for part of its length outside the coil; applying power pulls the plunger into the coil. Electromagnets with fixed cores are not considered solenoids.
The term solenoid also refers to any device that converts electrical energy to mechanical energy using a solenoid. The device creates a magnetic field from electric current, and uses the magnetic field to create linear motion.

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  1. D

    Field outside a solenoid on its axis

    Homework Statement A tightly wound solenoid of length L and radius a that has n turns of wire per unit length carries a current I. Calculate the the magnitude of the magnetic field at a point P on the axis of the solenoid, outside it and a distance y from one end, as shown in the figure...
  2. W

    The current and magnetic field of an ideal solenoid.

    This is not a homework question, it's just to help my conceptual understanding of two quick things: Suppose you have an ideal solenoid placed horizontally in front of you. The current is traveling (spiralling) from your left to your right. What direction is the magnetic field inside the...
  3. N

    Finding induced emf of solenoid

    Homework Statement A 800-turn solenoid, 18 cm long, has a diameter of 2.9 cm. A 15-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 3.1 A in 0.28 s, what will be the induced emf in the short coil during this time...
  4. K

    The rate of current through a solenoid - clarification needed.

    Homework Statement http://www.aijaa.com/img/b/00106/3735947.jpg Homework Equations \epsilon =- \frac {d \Phi}{dt}=- \frac {d BA}{dt}= \oint \vec{E} \cdot d \vec{l} B= \mu _0nIA , where n is solenoid's turns per meter. The Attempt at a Solution I was able to solve this through trial and...
  5. S

    Trying to achieve at least 1 Tesla for a solenoid

    I am trying to produce a magnetic field with a flux density of 1 Tesla through a solenoid with an iron core and I am having trouble crunching the numbers. I may also be doing the wrong computations. I am not too sure of the permeability of the iron core, I've seen different values, one being the...
  6. Y

    Current induced in loop - treat like a solenoid?

    Homework Statement A long straight wire lies below to a circuluar loop of wire. The straight wire is carrying a constant 10A current to the right. What is the magnitude and direction of the current in the circular loop, if its diameter is 1 m and its center is 0.75m away from the wire...
  7. H

    Mutual Inductance of solenoid and coil

    Find the mutual inductance (H) of the solenoid and coil shown below. The solenoid has 5263 turns per meter and an area 112 cm^2, and the coil has 230 turns and an area 19 cm^2. I know that mutual inductance = (N1 Φ1)/ I2 but I have no idea where to begin since they don't provide the...
  8. G

    Magnetic Field of an Infinite Solenoid

    The question is basically asking you to find an expression for the magnetic field of an infinite soleniod, through the center of the solenoid(lengthways), and around the coils of the soleniod. I know, with help from te textbook, that the magnetic field of a loop is 2(pi)b^2I/cr^3. Where b is...
  9. L

    Can Symmetry Arguments Simplify Ampere's Law for Solenoids?

    I need to use Ampere's Law and Gauss' Law to show that inside a solenoid B_r=0,B_\theta=0,B_z=0 i tried using cylindrical polars on ampere's law but the expression just got really long and i couldn't see any way out of it.
  10. J

    How Do You Choose Wire Type and Calculate Potential Difference for a Solenoid?

    Homework Statement You want to construct a solenoid 20cm long that has an interior magnetic field Strength B (Bc) of about 1.5MN/C. The coil has to be wound as a single layer of wire around a form whose diameter is 3.0 cm. You have two spools of wire handy. #18 wire has a diameter of about...
  11. R

    How Does Material Permeability Affect Force in a Solenoid's Magnetic Field?

    Force Inside a Solenoind ? Hello I'm working on a personal project which involves a solenoid. I'm trying derive an equation for the Force(N) that an object would experience due to the flux density inside the coil. The flux density can be calculated relatively easily by the fallowing...
  12. T

    Magnetism - Quick solenoid question

    Homework Statement A 200-turn solenoid having a length of 25cm and a diameter of 10cm carries a current of 0.29A. Calculate the magnitude of the magnetic field B inside the solenoid. Homework Equations B = \mu0ni The Attempt at a Solution Well, I plugged the numbers into the...
  13. A

    Simple Solenoid Problem Solution Using Ampere's Law

    Homework Statement the question can be found here: http://www.mailfreeonline.com/uploader/CED0D65C.jpg Homework Equations ampere's law The Attempt at a Solution a. (is B the magnetic field?) B = uI/L; u = 4pi x 10^-7, I = 1, L = 2pi x 0.1 so B = 2 x 10^-6 ^ can anyone...
  14. J

    Questions about movement of a permanent magnet inside of solenoid.

    I have been doing some experimenting with a relatively short cylindrical permanent magnet and a solenoid with DC current applied. I would like an explanation as to why these two things happen. The OD of the cylindrical magnet is just a little bit smaller then the ID of the solenoid. Placing...
  15. B

    What Is the Magnetic Field Inside a Long Solenoid?

    hi, My homework is : Qualitative description of field due to long solenoid. I think I post in wrong box, that box is about the calculus problem, right? But I'm a new member and I don't know where to post my question. So if I'm wrong, I'm sorry, please answer me once and tell me the right box...
  16. I

    Non uniformly wound solenoid (no Mag. field?)

    I made two solenoids using the same amount of wire (1000ft of 24 AWG) around 2 identical bobbins. One of them I painstakingly wound the wire uniformly and tightly. This solenoid is strong enough to pull a steel rod into the middle of the core. The other I haphazardly wound as fast and...
  17. E

    Designing a Solenoid: Equations and Force Calculations

    I have to design a solenoid. It should be wound on some soft metal of certain permeability. It should have hollow inner dia that will be used to operate a gas valve. The problem is which equations should I use to design the solenoid. I also have to calculate the force that will be required for...
  18. E

    How can I calculate the inductance of a solenoid for my device?

    I have to make a solenoid to operate some device. Can anybody let me know what formula to use to calculate number of turns for a solenoid wound on some metal. I also want to calculate the force. Does this formula works B = uourNI/L & F = ILB
  19. B

    Flux Linkage with a coil in a solenoid

    Homework Statement A solenoid of cross-sectional area 2*10^-4 m^2 and length 0.5m having 500 turns is to be used to produce a uniform magnetic field some distance close to the center of the solenoid. Find the current that must flow in the solenoid to produce a magnetic flux density of 3*10^-3...
  20. T

    Compass in a solenoid, oscillating

    Homework Statement A compass, consisting of a small bar magnet resting on a frictionless pivot through its centre, is placed in the middle of a long solenoid, which in turn is aligned with its axis pointing North-South. With a current of 1 Amp passing through the solenoid, a small...
  21. S

    Designing a battery operated solenoid

    I want to develop a solenoid for push application. the required push is around 5kg by electromagnet. We can use a combination of permenant magnet and electromagnet to optimize the design with respect to area and power consumption. For eg. the solenoid can push a permenant magnet also...
  22. C

    Magnetic field in an AC Solenoid Coil

    Hi.. I have a question about AC magnetic field, wondering if you can help me understand this. For a DC solenoid coil, We can say Magnetic field H=N*i/L (simplest form) For an AC input, H=N*isin(wt)/L ; H(rms) = N*i/L (i is RMS value) As long as the current i-rms is kept constant...
  23. S

    Calculating Electrical Parameters of Solenoid Coil for Spring Force

    I want to calculate the electrical parameters of solenoid coil of a valve for a given spring force. I know the force required to pull the solenoid plunger through a given distance against a spring, is there any formula to find out the required voltage, number of turns of coil winding & current .
  24. P

    Solenoid with a magnetic core

    1. Homework Statement A long solenoid with 70.0 turns of wire per centimeter carries a current of 0.100 A. The wire that makes up the solenoid is wrapped around a solid core of silicon steel (Km=5200). (The wire of the solenoid is jacketed with an insulator so that none of the current flows...
  25. P

    Solenoid with a magnetic core problem

    Homework Statement A long solenoid with 70.0 turns of wire per centimeter carries a current of 0.100 A. The wire that makes up the solenoid is wrapped around a solid core of silicon steel (Km=5200). (The wire of the solenoid is jacketed with an insulator so that none of the current flows...
  26. M

    The Magnetic Flux through a Solenoid

    Homework Statement Find the magnetic flux through a solenoid of length 31.2 cm, radius 1.5 cm, and 610 turns that carries a current of 3.8 A. (in Wb) Homework Equations B_solenoid=u0*N*I/L Flux= B *A The Attempt at a Solution So to find the magnetic field, I plugged the...
  27. R

    Finding turns per meter in a solenoid

    Homework Statement The magnetic field produced by the solenoid in a magnetic resonance imaging (MRI) system designed for measurements on whole human bodies has a field strength of 4.0 T, and the current in the solenoid is 300 A. What is the number of turns per meter of length of the...
  28. J

    Induced current of a coil surrounding a solenoid

    Homework Statement A coil with 170 turns, a radius of 5.0 cm, and a resistance of 12 ohms surrounds a solenoid with 230 turns/cm and a radius of 4.7 cm; see the figure. The current in the solenoid changes at a constant rate from 0 to 1.8 A in 0.11 s. Calculate the magnitude and direction of...
  29. G

    What is the Motional EMF in a Solenoid with a Square Loop Inside?

    Homework Statement A square, single-turn wire loop 1.00 cm on a side is placed inside a solenoid that has a circular cross section of radius 3.00 cm, as shown in the figure below. The solenoid is 16.0 cm long and wound with 95 turns of wire. (a) If the current in the solenoid is 3.00 A...
  30. A

    Primary solenoid with secondary coil effect? if any?

    primary solenoid with secondary coil...effect?? if any?? A primary solenoid of 1200 evenly spaced turns is wound on a cylindrical former 800mm long and 30mm in diameter. A secondary coil of 10 000 turns is wound around the central portion of the solenoid. A steady current of 2A is flowing in...
  31. 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...
  32. A

    Magnetic flux through loop inside of solenoid

    Homework Statement A solenoid has 1800 turns of wire and is 125 cm long and 10.0 cm in diameter; see Figure P.14 (attached). A circular wire loop of diameter 5.0 cm lies along the axis of the solenoid near the middle of its length as shown. (a) If the current in the solenoid initially is...
  33. A

    Elec & mag, current wire in solenoid

    Homework Statement I took pictures of the problem with my camera, along with my solution. I couldn't get the picture to show on here, so I uploaded them to my myspace. please look at the pics in the links! the problem...
  34. N

    Solenoid equation derivations

    Homework Statement Consider a solenoid of length L, transverse area A, total number of loops N Compute the magnetic field B inside the solenoid, assuming that it is uniform and vanishes outside the solenoid, neglect any boundary effects. Working under the same assumptions, calculate...
  35. K

    Is There a More Accurate Equation for the Magnetic Moment of a Solenoid?

    Does anyone have an equation that describes the magnetic moment of a solenoid that does not actually use number of turns as an input? I'm trying to validate a solenoid I have made with something like 11000 turns, but I'm not sure how accurate my number of turns in, so I need a second input...
  36. B

    What Path Does a Charge Take in an AC Solenoid?

    Hi, I was wondering about the path a charge placed in a solenoid that was flown through by alternating current would take. Would it move on a circularly? Thanks!
  37. C

    Solenoid flux-emf-current problem

    Homework Statement A solenoid inductor has an emf of 0.20 V when the current through it changes at the rate 10.0 A/s. A steady current of 0.10 A produces a flux of 5.0 microWb per turn. The number of loops in the solenoid is the value which needs to be found. Homework Equations...
  38. U

    How Can Current Influence Magnetic Field Strength in a Solenoid?

    Hey guys, I'm really having problems with this. Normally I get pretty good grades but this just has me completely stuck. It's hard because I have to design something, yet it doesn't seem like there's a lot of easily understanable information out there to draw from. Any help would be greatly...
  39. J

    Why Does Steady State Current in a Solenoid Exceed Initial Pull-in Current?

    Why is the steady state current through a solenoid greater than than the current when the plunger is first fully pulled in? I would expect it to be identical to the low peak in the current profile when the plunger hits the stop when fully engaged. Thank you, Jorge
  40. K

    Solenoid length of wire problem

    Hey so I have been trying this problem and just cannot get it. thanks for the help. To construct a solenoid, you wrap insulated wire uniformly around a plastic tube 12cm in diameter and 55cm in length. You would like a 2.0A current to produce 2.5kG magnetic field inside your solenoid. What...
  41. S

    B-field of ideal cylindrical solenoid, using Biot-Savart.

    Homework Statement Consider an ideal cylindrical solenoid of length L and radius a=L/2 on which a thin wire has been wrapped a total of N turns. A steady current I flows through the wire. Assume the wires are wound so tightly that the solenoid can be thought of as a collection of N parallel...
  42. clope023

    Magnetic Field at a distance from the center of a Torodial Solenoid

    Homework Statement A torodial solenoid has inner radius r1 = .15m, outer radius r2 = .18m; turns N=250 and carries a current I = 8.50A. What is the magnitude of the magnetic field at the following distances from the center of the torus? a) .12m b) .16m c) .20m Homework Equations...
  43. L

    How can I calculate the temporal characteristics of a pulsed solenoid circuit?

    Hello! I wonder if anyone can give me some quick advice. I'm designing a physically small (but high current) pulsed solenoid. The circuit will basically be an RLC circuit where a switch is thrown to discharge the capacitor into the coil, giving a strong short-lived magnetic field. I'm...
  44. S

    Loop and solenoid, find the current

    Homework Statement a single loop is placed deep within a 4 meter long solenoid having a total number of turns equal to 40000. the loop has an area od 0.01m^2 and it carries a current of 20 ampere. the loop is oriented so that the torque on the loop is a maximum with a magnitude of pi*10^-4...
  45. T

    Magnetic field in a semi-cut solenoid

    Im just curious as to how the magnetic field would be for a semi cut solenoid as shown in the diagram below. The Solenoid covering is partially cut and the soft core iron in the solenoid is also cut and the number of windings in the area decrease considerbly.. The winding on either side...
  46. J

    Deriving Magnetic Field Through Solenoid Using Amperes Law

    [SOLVED] Amperes Law Homework Statement Deriving the magnetic field through a solenoid. Homework Equations dB = mu0/4pi x Idlsintheta/ r^2 where I = current dl= a tiny change in length dB = a tiny change in flux density sintheta is the angle to the normal r is the radius mu0 is the...
  47. L

    Core material selection for high-current DC solenoid

    Hello! This is my first post on Physics Forums. Seems like a good community. I will endeavour to contribute. Over the next few weeks I will have to build a test rig for a fiber-optic sensor I'm developing. The sensor is for high magnetic field strengths, so the test rig must essentially...
  48. B

    Can Adjacent Coils in a Solenoid Touch Without Affecting Its Functionality?

    To create a solenoid, conductive wire is coiled with n # of turns per unit length. To create a real solenoid can each coil touch the adjacent coil or does there have to be some non-conductive material between them? The reason I ask is it seems if they were touching that current would flow...
  49. A

    New to Maxwell & FEM: Magnetostatic Analysis for Solenoid Valve

    Dear all, I'm a new user to Maxwell and to FEM. I am trying to do a magnetostatic analysis for a solenoid valve for finding inductance and force on the armature. I am facing few problems while making the simulation. 1. what value shall I assign for the source? (In the tutorial provided by...
  50. T

    Magnetic field at the center of a solenoid?

    A studetn needs to make a solenoid that produses 1.09 T at its center. a wire will be wrapped around a solid cylinder of iron with a relative permeability Km of 1400, a length of 13.3 cm and a radius of 1.92 cm. if the wire can carry a max current of 1.15 A how many turns of wire are neede to...
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