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. Silent_88

    How to make a device which is "Reverse solenoid"

    Hi Everyone, This is Sentil from India. I'm a professional in the field of commerce. But i love science! then the obvious question "Why /How did you end up in Commerce". Thats really a long story. But today I am here to get help on one of the side projects i am into to develop something like...
  2. U

    Where Can I Find an Astable Linear Solenoid for My Robotics Experiment?

    I enjoy doing kitchen engineering with my kids. We were looking to do a robotics experiment which would require a linear solenoid actuator to continuously pump. I thought it would be simple until I realized that I would likely need a 555 chip(?) and some skills with circuitry...which would be...
  3. U

    How to get a linear solenoid actuator to cycle?

    Hi, I am working on a project with my daughter who is 10. We are trying to get a linear solenoid actuator (push) to continuously repeat (push/return...push/return). But all it does is push and stop. How do I get the wiring set up to enable the solenoid to automatically cycle? Thanks!
  4. P

    Curl of the vector potential produced by a solenoid

    Homework Statement / Homework Equations[/B] I was looking at Example 5.12 in Griffiths (http://screencast.com/t/gGrZEPBpk0) and I can't manage to work out how to verify that the curl of the vector potential, A, is equal to the magnetic field, B. I believe my problem lies in confusion about how...
  5. B

    Formula of Solenoid Magnetic B-field at Ending, Middle and Outside

    Can anyone way in on the correct Formulas of a Solenoid Magnetic B-field at Ending, Middle and Outside? I have the following so far but some of them seem to contradict one another . Photo #1: Photo #2: Photo #3: Photo #4: Photo #5: Photo #6:
  6. Mr. Rho

    Poloidal current in toroidal solenoid

    Hi, I'm trying to figure out how the current density for a poloidal current in toroidal solenoid is written. I found you may define a torus by an upper conical ring ##(a<r<b,\theta=\theta_1,\phi)##, a lower conical ring ##(a<r<b,\theta=\theta_2,\phi)##, an inner spherical ring...
  7. C

    Very Large Diameter Electromagnet (solenoid)

    I am toying with an idea and not sure if it's feasible. Here is the setup: There is a 6' diameter steel pipe that is 30' long standing up vertically. Inside, among other stuff, are ~20 small 'trolleys' on tracks that run from top to bottom, spread out evenly among the cross sectional area of...
  8. B

    Magnetic B Field Equation Due To Multi-Layer Solenoid

    Anyone knows the Magnetic B Field Equation Due To Multi-Layer Solenoid(with a core) ? where: Core Material "μ" is of radius R1(NOT shown in the below drawing) i - Current μ - Permeability (of Core Material)All length, diameter and pitch measurements are from centre to centre of the conductors...
  9. Mr Davis 97

    Use of a solenoid for inductance

    Although I'm sure the answer is obvious, but why are solenoids used as inductors? Why don't entire circuits in general have inductor properties, since the entire circuit creates magnetic fields? More specifically, why don't random points along a circuit do the same thing as a solenoid (retain a...
  10. A

    A coil of 25 turns of wire is suspended by a thread

    Homework Statement A coil of 25 turns of wire is suspended by a thread. When a current flows through the coil, the tension in the thread is reduced by 4.0 ´10-2N. http://members.shaw.ca/barry-barclay/Self-Tests/test11/Magnet20.gif Homework Equations F=IBL B=nμI[/B]The Attempt at a Solution...
  11. P

    Design 1.5 A Solenoid & Charge 1.5 V Battery

    Hey All, I'm trying to design a solenoid that would generate about minimum 1.6 A of current in order for me to charge up a 1.5 A 1.5 V battery. I already designed one which is about 10CM in length and unknown number of turns (as I used a drill to wind the coils around it. so I would guess its...
  12. R

    Does a solenoid wrapped around a magnet meet resistance?

    If a solenoid were wrapped around a bar magnet, and a charge were applied through the solenoid, would there be resistance?
  13. N

    Law for magnetic field due to solenoid

    Homework Statement Just a quick clarification about the law: B = 4pi * 10^-7 * n *I/LDoes n refer to total number of loops, or just the number of loops in a single layer? Like, If I have a solenoid that's made up of 4 layers and 1000 total loops, do I plug in 1000 or 250?Homework EquationsThe...
  14. theodoros.mihos

    Why we calculate B of solenoid with this way?

    We see the magnetic field calculation by Biot-Savart law for a circular current I on some distance z on the vertical axis throw it centre as: $$ B(z) = \frac{\mu_0I}{2}\frac{r^2}{(r^2+z^2)^{3/2}} $$ where r is the radius of circle. When we use summation of N rings lays on L length, like...
  15. B

    Magnetic field of moving solenoid

    If a solenoid oriented on the z axis is carrying a steady current, I if will produce a constant B field inside of the solenoid. A charged particle with initial velocity perpendicular to the z axis will undergo cyclotron motion within the solenoid at a constant radius, r. What are the electric...
  16. Alettix

    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...
  17. Nile Anderson

    How does one calculate the flux density B at end of solenoid?

    Homework Statement I came across a recent problem that asked me to calculate the flux density at the end of a solenoid. I was given the current 3 A , the number of turns per unit length , 12 cm-1 and the using the permeability of free space as 4π × 10^-7 Homework Equations The equation I used...
  18. A

    Magnetic field solenoid with diamagnetic core

    For a solenoid as on the picture with a diamagnetic in the middle, the total B-field generated will come from both the free currents inside the solenoid as well as the induced magnetic field from the diagmagnetic material. But will the magnetic field attributed to the bound currents inside the...
  19. Nile Anderson

    How do you determine the polarity rods placed in a solenoid?

    Now well the question is pretty straight forward , and please do not pass this by , I am in high school but I am a still a very accomplished physics student. I am currently doing Magnetism and I came by a question , where people are saying a solution that seems very counter-intuitive to me...
  20. G

    Magnetic field inside a solenoid

    Could someone check my calculations? Homework Statement Calculate intensity of magnetic field inside of solenoid, who is made from 1mm thick copper wire with 28 twines(n=28). Solenoid is 25 cm long, diameter - 4 cm, and it`s connected to 24V DC voltage. U=24V ; n=28 ; ρ for copper =0,0175...
  21. H

    Coil vs Solenoid: Understanding the Difference and Equations for Magnetic Fields

    Homework Statement I'm having problems figuring out the difference between a coil and a solenoid. My book provides two equations for magnetic field, and they are similar, but one depends on the radius (coil) while the other depends on the length (solenoid). Homework Equations Bcoil = μNI/2a...
  22. R

    Transient FEM Simulation of a Solenoid Actuator with MAXWELL

    Hey Guys! Hi Guys! Well I am new here and I have to confess that I somehow got stuck in a 3D transient electromagnetic simulation of a solenoid actuator and… I’m a mechanical engineer^^ So I would appreciate some help of you guys! 1. I imported the geometry from CAD-files. But I remodeled...
  23. W

    How to Calculate Induced EMF in a Wire Loop Near a Solenoid

    Homework Statement A solenoid has 500 turns per meter and cross-sectional area 4cm2 Current through it is increasing at 100A/s and flows in a clockwise direction. There is a wire loop, concentric with the solenoid which sits outside the solenoid. Given that the magnetic field inside the...
  24. S

    Working with magnetism, solenoid

    Homework Statement A bar magnet is held stationary (with respect to the loop of wire) at the centre of the loop with the North pole sticking out one end and the South pole sticking out the other. What happens to the size of any EMF induced in the loop once the magnet has been replaced by a...
  25. EddieP

    Magnetic powder in a solenoid - how would it react?

    Suppose I have a plastic tube about 70% full with magnetic powder, with a copper coil solenoid around the cylinder. By "magnetic powder" I mean each particle is actually a tiny permanent magnet with its own magnetic field. - like you can see in this video When there is no externally applied...
  26. Euler2718

    Solenoid Field Strength - Missing Raduis?

    Homework Statement A long solenoid has 35 turns/cm. With a current of 4.0A, what is the field strength at the core? Homework Equations \beta = \frac{\mu N I}{2r} The Attempt at a Solution I have no idea with the radius is; that's the entire problem statement above.
  27. jlefevre76

    Understanding the Physics of a Coilgun: A Beginner's Guide

    Hey, I've seen a few posts on this without any responses I really thought helped (at least help answer my question). So, I was hoping somebody on the forums here could help walk me through the basic physics of a coilgun. Basically, how could you characterize the magnetic field inside the...
  28. C

    How Coulomb's Law relates to generators? (voltage)

    Homework Statement In science class, we are supposed to explain how a generator works and functions. However, we have to incorporate coulomb's law in our explanation. Homework Equations F=kQ1Q2/r^2<-- coulomb's law The Attempt at a Solution How I understood it was that a generator consists of...
  29. EternusVia

    Solenoid Electricity Generator

    Hi all, I'm trying to generate enough current using a solenoid to intermittently power an LED. My plan is to buy some enameled copper wire and wind it around pipe. This will be my solenoid. Then, magnets will be pulled through the pipe on string or what-not and, by Faraday's Law of Induction...
  30. hackhard

    Electromagnet to attract small iron pieces

    i want to build an electromagnet which can attract small iron pieces(2-3 mm long) at a distance of 10 cm from the magnet.I am using 24 awg. magnet wire.Please help .answer these questions - 1) How long magnet wire (24 awg) do i need? 2)How much current 3) what shud be least radius of solenoid 4)...
  31. Shinwasha

    Time it takes for electron to travel through a solenoid.

    Homework Statement An electron enters a solenoid at 65 degrees below a solenoid. The solenoid has a 10 A clockwise current is 33.0 m long and has 400 turns. Ignoring end effects what is the shortest amount of time in which the electron pass through the solenoid? Homework Equations Only one I...
  32. S

    Need help with a 12v solenoid

    I'm not so smart when it comes to electrical things, so please forgive my ignorance. Here's what I am trying to do. I have a quad axle dump truck, I'm trying to have the drop axles automatically come up when put into reverse. The drops are raised and lowered via 2, 12 volt solenoid valves. I...
  33. inversquare

    Solenoid Magnetic Field Testing

    Any recommendations for getting an accurate reading of a magnetic field in a solenoid coil? They're ferrite cores wrapped with magnetic copper wire. Would putting a Hall sensor at the end of the ferrite be a reasonable way to do this? Or will the field have already diverged? (The coil stops...
  34. inversquare

    Ferrite Rod Geometry for Magnetorquer Design

    Hello! We are working with some ferrite rods to build solenoid magnetorquers for a cubesat design. The geometry on these rods is unique. Are there benefits to this type of a geometry? They are 19.6 cm length x .67cm diameter.
  35. EddieP

    Calculating magnetic field for a micro solenoid

    I am trying to calculate the magnetic field (in tesla/gauss) of an iron core electromagnet that is very small and has very few windings. For example 12 windings over 0.003 meters. I know this is not going to produce a very strong field, but I would like to pulse a strong current through the coil...
  36. rothran

    Measuring magnetic field of a solenoid relative to distance

    So, I recorded the result of a LabQuest 2 Vernier Magnetic Field Sensor on different points of a plane, with a solenoid in middle with a 5 amp current running through. I want to compare my results with theory, but have no idea what equation I'm supposed to be using. I assumed it was B = μ0ηI/r3...
  37. S

    Calculating current through solenoid?

    Not for a class or anything, just out of curiosity, how would you calculate the current in a solenoid, not given a magnetic field, but just using a bar magnet? I know it will just be some form of Faraday's law. E=N(dphi/dt). Maybe not. I'm imagining all I'm really missing is how to calculate the...
  38. Misha Kuznetsov

    Why Doesn't a Magnet Simply Get Forced One Way or Another in a Solenoid?

    The field lines inside of a solenoid all go in one direction, right? So why doesn't a magnet that's placed in the solenoid simply get forced one way or another. I tried this at home by placing a magnet in the solenoid(near the outside of the coil so that it stuck out a bit), and when I turned on...
  39. M

    Magnetic field in a multi-layered solenoid

    Hello everyone, this is probably a simpler problem than I think but here it is My argument is that the length of the solenoid is the number of turns times the diameter of the wire so B=\mu_{0}\times n\times I\\\\ =\mu_{0}\times \frac{N}{L}\times I\\\\ =\mu_{0}\times \frac{N}{N\times d}\times...
  40. X

    Solenoid vs transformer inductance

    When they teach transformers, they give you the Ampere's law, the Faraday's law, etc. and then derive this well known formula L = μ * N^2 * A / ℓ. And everything is no nice, all these parameters are used to define some other relationships, like the concept of reluctance in magnetic circuits...
  41. N

    Magnetism, Credit-Card magnetic strips

    Homework Statement Experiments carried out on the television show Mythbusters determined that a magnetic field of 1000 gauss is needed to corrupt the information on a credit card's magnetic strip. (They also busted the myth that a credit card can be demagnetized by an electric eel or an eelskin...
  42. Prashasti

    Magnetic field inside a Solenoid

    Homework Statement Can I derive an equation for magnetic field inside a solenoid using the formula for magnetic field on the axis of a current carrying coil? Homework Equations B = μI/2r ( Magnetic field at the centre of a current carrying coil)The Attempt at a Solution B = μI/2r Let the...
  43. T

    Alternate to a proportional linear solenoid

    I am trying to build a circuit using gears, motors, and relays only which mimics the motion of a proportional linear solenoid i.e. Hold a spring compressed at a certain distance depending on the current passed, and push/ release it further based on the increase/ decrease of current. (V=12 V...
  44. R

    How the solenoid gets the linear motion when the current is passed in the coil?

    The Solenoids which are used for pneumatic controller uses the solenoid as a switch to control the value opening and closing. This is done by passing current to through the coil which produces the magnetic field . But i would like to know how the generated magnetic field will move the solenoid rod?
  45. A

    How to Select a Solenoid for Tensioning a Chain on a Rotating Bobbin?

    I need to select a solenoid actuator for tensioning a chain. The chain is for a bobbin which rotates at 100 rpm. The weight of the bobbin is 9081 kgs. I calculated the braking torque of 35 KN-m but as my knowledge is very limited for solenoids i wish to know how can i select a solenoid for this...
  46. P

    How Does Induced EMF Vary Inside a Solenoid?

    Homework Statement The current in a solenoid (you may treat it as a long solenoid of length 2.0 m, turns, and radius 0.5 m) is decreasing at a rate of 1.7 A/s. What is the EMF at a point .35m inside the solenoid? Homework Equations B=N(mu_0*I)/(2a) where B=magnetic field, N=turns per...
  47. paulina

    Net current in a solenoid or torroid

    The notion of multiplying the current in each loop in a toroid or solenoid with the total number of loops in order to find out the net current in the toroid or solenoid is appearing a bit confusing. Why do we do this when we know the same current is flowing through each loop (just like water...
  48. J

    Can you use multiple wires to wind a solenoid?

    I am curious if an alternating solenoid coil needs to be wound with a single piece of wire from end to end, or - can each loop in the solenoid be made of a separate wire and stacked on top of the previous, as long as each termination is connected to the proper + / - terminal. Essentially - is...
  49. V

    Electric field inside solenoid

    Hello, I am trying to find out the electric field inside a solenoid if a time varying current is passed through. However I am stuck with these partial differential equations. Somehow I can't solve them and I think something is wrong. Because according to equation (13) the electric field will...
  50. F

    Inductance of Multilayer Solenoid

    I've been looking for a good formula to calculate the inductance of a multilayer solenoid within about 10% accuracy or greater. I've used several formulas derived from Wheeler's formula, as well as a few online calculators, however, my results seem to differ wildly depending on what formula or...
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