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. H

    Eddy current in an infinitely long cylindrical conductor in an solenoid

    Problem: Calculating the eddy current distribution inside an infinitely long cylindrical conductor inside a straight and infinitely long solenoid energized by an alternating sinusoidal current. The problem has a perfect summery and we know that magnetic field and the eddy current depend on...
  2. P

    Poynting Vector - Finding stored energy per unit length of a solenoid

    Homework Statement long solenoid of n turns per unit length is wound upon a cylindrical core of radius a and relative permeability. The current I through the solenoid is increasing with time t at a constant rate. Obtain expression for the rate of increase of stored energy per unit length...
  3. M

    Velocity of electron shot from a solenoid.

    Homework Statement A certain solenoid(50cm long with 2000 loops) carries a current of 0.70A and is in vacuum. An electron is shot at an angle of 10deg to the solenoid axis from a point on the axis. Find the speed of the electron if it is just to miss hitting the inside of the 1.6cm diameter...
  4. P

    Magnetic Field and Force (in a solenoid)

    Homework Statement A 200-turn solenoid is 20.0 cm long and carries a current of 3.25 A. Find the magnetic field. Find the force exerted on a 15.0 µC charged particle moving at 1050 m/s through the interior of the solenoid, at an angle of 11.5° relative to the solenoid’s axis. Homework...
  5. W

    Finding the force of a magnetic field using an air core solenoid

    Homework Statement Ok, I need help, but it is for a project my son is working on. I am homeschooling him (13) and he is entered in a local science fair. He has designed an air core solenoid shock absorber for a bike. It more or less works, and we are working our way through the forces...
  6. A

    How Relevant Are 1960s Solenoid Design Principles Today?

    Hey everyone, I'm looking for some references on solenoid design - core materials, geometry, etc etc etc. Can anyone suggest me some canonical references that I should check out? All the books I've found are from the 60s or so. Thanks!
  7. P

    Inductance Of A Solenoid Problem

    Homework Statement A solenoid is wound with a single layer of insulated copper wire of diameter 2.100 mm and has a diameter of 3.000 cm and is 1.900 m long. Assume that adjacent wires touch and that insulation thickness is negligible. a) How many turns are on the solenoid? Solved...
  8. S

    Magnet in a AC current solenoid

    when you place a magnet into a solenoid with a ac current it will get demagnetised. So does this mean that the magnetic field will go into the magnet in the opposite direction of the magnet's own magnetic field? and disalign it. meaning will the magnetic field enter the magnet as though it is...
  9. N

    HiI know that for a short solenoid (L<R) the magnetic field at the

    Hi I know that for a short solenoid (L<R) the magnetic field at the axis is (standard EM) B(z) = \frac{1}{2}\mu_0 \frac{N}{L}I(\frac{z+\frac{L}{2}}{\sqrt{(z+L/2)^2+R^2}} - \frac{z-\frac{L}{2}}{\sqrt{(z-L/2)^2+R^2}}) where R is the radius of the solenoid, N the number of turns along the axis...
  10. R

    Home applications that use a solenoid?

    Hi, Can you name a few house hold items that have a solenoid in them?APART FROM A DOOR BELL. Especially those which can be carried in hand. Thanks.
  11. N

    Force on solenoid in external uniform field?

    A solenoid, of sufficient length to consider external flux to be zero, passes through a uniform magnetic field with significant length on both ends extending beyond the field. Will a torque be exerted upon the solenoid ? Or do the windings effectively mask the internal solenoid field from the...
  12. M

    Solenoid; high-speed push and pull

    Hi all. I am going to build an industrial quality knife-tool to cut cardboard, and I would like to ask you all for any advice, experience and warnings you might have. I'm in the need of a motor to oscillate a knife at a frequency of 200-300 Hz, with a stroke of 1.2mm +/- 0.6mm. The knife it...
  13. M

    Magnetic field outside a solenoid crossed by a current.

    Homework Statement A student makes an electromagnet by winding 320 turns of wire around a wooden cylinder of diameter 4,80 cm. The coil is connected to a battery producing a current of 4.20 A in the wire. At what axial distance z>>d will the magnetic field of this dipole be 5.0 μT? Homework...
  14. F

    Magnetic Field From a Solenoid - Biot-Savart Law

    I'm fairly confident I can express the strength of a magnetic field along the axis of a current carrying loop at some distance x away using the Biot-Savart Law. I'm just trying to extend this idea for a solenoid with N turns. I'm assuming that the current would become NI in this case? Regards Dan
  15. C

    E&M Solenoid and Capacitor problem

    Homework Statement Consider a large solenoid aligned with the z-axis with a uniform magnetic field inside given by Bo = Boz[hat]. Contained WITHIN the solenoid is a very large parallel plate capacitor and the plates (one at the x=0 plane and the other at the x = d plane) have surface charge...
  16. S

    How Can I Calculate the Energy Requirement for a Lateral Solenoid?

    Sorry to bring this up again but is there any way of telling how much energy a solenoid will use for a lateral solenoid for a given length and diameter. Is there an online calculator? I'm interested to know how much energy is lost in the form of resistance/heat as my understanding of how they...
  17. R

    Direction of force on bar magnet in solenoid

    A bar magnet with uniform magnetization is inserted half way into a solenoid, and I am wondering what the force is on the magnet? The magnet's magnetization is pointing up, which means it has bound surface current circling counterclockwise, and a magnetic field pointing up. The solenoid...
  18. P

    A 2cm diameter cylindrical solenoid of 10 loops and 20cm long

    Homework Statement A 2cm diameter cylindrical solenoid of 10 loops and 20cm long is in a perpendicular magnetic field of 0.7Tesla directed away from you. The field increases to 2.7Tesla in 100ms. The loop has 8Ω. What is the EMF? What is the current? What is the magnetic field of the...
  19. W

    Solenoid electromechanical problem

    Homework Statement We have a solenoid and power supply and a plunger with a mass, Determine y(t) when v(t)=U(t) (i.e the movement of the plunger when the input voltage is the unit step) use laplace transformes for the current i(s) and for the movement of the mass for a given force. Probel...
  20. L

    Solenoid Magnetic Field Problem

    A solenoid of length 45 cm has 340 turns of radius 2.2 cm. A tightly wound coil with 16 turns of radius 4.4 cm is at the center of the solenoid. The axes of the coil and solenoid coincide. Find the emf induced in the coil if the current in the solenoid varies according to I=4.6sin(50∏t)A...
  21. T

    Magnetic field at a point due to two wires and a solenoid.

    Homework Statement The point p is located at (3,1,2). An infinitely long straight wire passes through the points (0,0,0) and (0;1;0) and carries a current of a A in the positive y direction. A finite length of wire carries a current of b A from (2,0,0) to (2,0,0). An semi-infinite solenoid...
  22. W

    Mutual inductance of a solenoid wrapped around part of a toroid

    *This isn't a problem so much as needing to fill in the gaps from a lecture where I was taking notes on painkillers due to surgery. The problem statement is my best guess as to what exactly was said by the instructor. Homework Statement "Find the mutual inductance (M) of a square-bore...
  23. jegues

    Magnetic Field Outside Infinite Solenoid

    Homework Statement See figure attached. The author claims the field outside this infinitely long solenoid with N' turns and a current i(t) flowing through it is 0, but he doesn't explain why. Why is it 0? Is there an intuitive reasoning behind it? Homework Equations N/A The...
  24. J

    Calculating Induced Current and Force in Moving Magnet Over Solenoid

    can someone help with this calculation two semicircle magnets N-S of strength 'B' encircle a solenoid of length 'L' and move with a constant velocity 'V'. what will be the current 'I' that is induced in solenoid. also, what force will the magnet experience because of this current (Lenz's law)
  25. I

    Choosing a Solenoid for A2 Level Product Design

    I am doing A2 Level Product Design (as well as Physics obviously ) and I am making a workstand for a bicycle. It involves a ratchet and pawl mechanism which will be locked out by a solenoid acting on the pawl. The bike weighs roughly 12.1kg and the ratchet wheel from nylon. The pawl is...
  26. I

    What Type of Solenoid is Best for My Bicycle Workstand?

    I am doing A2 Level Product Design (as well as Physics obviously :tongue:) and I am making a workstand for a bicycle. It involves a ratchet and pawl mechanism which will be locked out by a solenoid acting on the pawl. The bike weighs roughly 12.1kg and the ratchet wheel from nylon. The pawl...
  27. F

    Number of Turns Needed for a Good Solenoid

    Hello Forum, How many turns do we need to make a good solenoid? 50, 40 ,1000? I know the more turns, the larger N, the better. But what is the minimum number of turns to create a homogeneous B field inside the coil and an almost zero B field outside? Does the cross-sectional area of the...
  28. P

    Induced Solenoid Voltage by external magnetic fields

    Homework Statement In my physics lab, we were asked to connect an unpowered solenoid to an oscilloscope and then move a magnet through the solenoid and observe the changes in voltage on the oscilloscope. First we were asked to move the north pole of the magnet into the solenoid and then the...
  29. R

    Building a solenoid need advice

    I'm intending on creating a solenoid that will project a bb for a class project. I'm using a flash capacitor from a disposable camera as my current source. Here is my question...what is the best "setup" for the solenoid to increase the magnetic force on the bb without increasing its current...
  30. J

    Solenoid, calculate number of coils

    Homework Statement We want to construct a solenoid with a resistance of 4.30 Ω and generate a magnetic field of 3.70 × 10−2 T at its center when applying 4.60 A of electrical current. We want to use copper wire with a diameter of 0.500 mm. If we need the solenoid's radius to be 1.00 cm...
  31. S

    Mutual Induction of a solenoid and a coil

    Homework Statement A single-turn circular loop of radius R = 0.235 m is coaxial with a long 1780 turn solenoid of radius 0.0435 m and length 0.850 m, as seen in the figure below. The variable resistor is changed so that the solenoid current decreases linearly from 6.12 A to 1.46 A in 0.230...
  32. S

    Mutual Induction of a solenoid and a coil

    Homework Statement A single-turn circular loop of radius R = 0.235 m is coaxial with a long 1780 turn solenoid of radius 0.0435 m and length 0.850 m, as seen in the figure below. The variable resistor is changed so that the solenoid current decreases linearly from 6.12 A to 1.46 A in 0.230...
  33. N

    Can Solenoids Be Used as Shock Absorbers Through Electromagnetic Damping?

    Is it possible to use a solenoid as a shock absorber? i.e run current through the solenoid, producing a magnetic field opposing a separate magnet attached to whatever it is receiving the shock impulse, thus dampening the effect according to the amount of current input.
  34. M

    How does the magnetic field strength decay(radially) inside a solenoid coil?

    I'm looking at redesigning a hydraulic solenoid valve with the aim of reducing the package size. The solenoid coil is by far the largest component of the device, with about 4000 coils arrayed in about 90 layers stacked on top of each other. I'm wondering if I can reduce the size by removing some...
  35. B

    Direction of electron flow in solenoid

    I'm having a bit of confusion applying the left hand rule to find the direction of electron flow in a coil. I'm given the following pictures. 1.) To use the left hand rule here, I would wrap my hand around the object with my thumb pointing towards the north pole, so my fingers would...
  36. C

    How would the magnetic field of a solenoid change if it used AC current

    How would the magnetic field of a solenoid change if it used AC current instead of DC current? How would this affect the motion of a charged particle moving from the center to the side of the solenoid? This isn't a homework problem, just something I'm curious about. Hence, there is no "right"...
  37. O

    Magnetic Field in Solenoid question

    Homework Statement Your physics lab demonstrator hands you a spool of copper wire and a battery (voltage V) and asks you to wind the wire around a hollow, cylindrical, cardboard tube (radius a) to make a solenoid of length 2L. a) What is the amplitude of the magnetic field at the centre...
  38. C

    Calculating the current in a solenoid

    Homework Statement A short-circuited solenoid of radius b with n turns rotates at an angular velocity about the diameter of one of the turns in a uniform magnetic field B. The axis of rotation is perpendicular to the magnetic field direction. The resistance and the inductance of the...
  39. A

    Magnetic Field Centre Of A Solenoid

    Homework Statement http://i27.lulzimg.com/ac8f155fa0.jpg [PLAIN][PLAIN]http://i27.lulzimg.com/b5f4ac2fce.jpg Homework Equations 1. B = ((mu(0) * N * I )) / L ,, 2. (mu(0) / 4pi)*((I*(delta(S) cross r(direction)))/r^2) The Attempt at a Solution im not really sure which...
  40. W

    Solenoid Question: Interlocking Coils & Back EMF

    Hi, I'm new to the forums, and I'm studying to be an aerospace engineer. I'm still in the start of my program, and I'm not in school till next semester, so this isn't for school. My question is, what's the effect of interlocking coils that are slightly offset carrying a current in the same...
  41. C

    Finding RMS current in an AC solenoid

    Homework Statement A 2000 turn solenoid of length 1.50 m and diameter 5.00 cm has a dc resistance of 3.0. It is connected to a 50 Hz, 40.0 Volt (rms) ac supply. Find the rms current in the solenoidHomework Equations Vind = L di/dt Vind = Induced EMF Ohm's Law V-Vind = IR L = (4pi x 10^-7)n^2 Al...
  42. F

    Induced emf as a magnet passes through a solenoid

    I'm doing a lab write-up for physics 2. The experiment is about the title, a bar magnet being dropped through a solenoid. I have to explain four graphs that plot the change in emf (y axis) vs. time (x) axis. There are incoming and outgoing peaks on these graphs. I have to tie these results...
  43. A

    Solenoid variable voltage/position problem

    I am attempting to build a device that pulls against a spring at variable tensions, based on how much electricity is passed to it. I have read that solenoids don't "like" being charged for long without going to a closed position. That they burn out. The specific problem is that the spring...
  44. S

    Magnetic Field Strength Calculation for a Solenoid with Given Parameters

    Homework Statement A 10 cm long solenoid with 241 turns and radius R = 3.00 cm has a current flowing through it of Io = 200 mA. What is the magnetic field strength inside the solenoid (in T)? The Attempt at a Solution So i know i have to use the formula B = (uo)(n)(Io) uo = a constant 1.257 x...
  45. ?

    EM attraction between a solenoid and interstellar hydrogen

    Okay I have a really odd question that might be difficult to answer. I have searched for an answer in several physics books and websites and don't think I have come across a specific answer for this question. Suppose I were to send a negative electromagnetic charge through a solenoid and want...
  46. R

    Constant Field Throughout Entire Solenoid Axis

    Along the center of a very long solenoid tube the field strength is constant. At the ends of the tube, however, the field decays and drops off. Is there a simple way (mathematical solution or simple trick) to make the field perfectly constant (or to a fraction of a percent tolerance)...
  47. W

    Exploring the Use of Solenoids in Railgun Technology: Pros and Cons Revealed

    I haven't seen any discussion or any mention what so ever of this before so excuse me if it's that's because it's a crazy idea. What would be the pros and cons of using solenoids as the rails and projectile of a railgun? Would the stronger magnetic field of the solenoids allow a stronger force...
  48. H

    Problem in determinig Poles of a Solenoid

    Hi Everyone, I have made a solenoid of 100 turns. When i bring a small permanent magnet near the solenoid, it attracts the North pole of permanent magnet while it should attract the South pole according to right hand thumb rule... now i got confused. Kindly help me. Regards, hsn
  49. H

    Calculating Initial Speed of 2.7g Ball Launched at 45° with 50V Solenoid Input

    Homework Statement A ball ( 2.7 g ) is launched at a 45 degree angle with a solenoid input of 50V. What is the initial speed of the ball? Homework Equations KE = 0.5mv^2 PE = mgh dy = vy(0)t + 0.5at^2 dx = vx(0)t The Attempt at a Solution Voltage is potential energy and I...
  50. K

    Electromagnetic Induction: Solenoid & Magnet

    I have just learned electromagnetic induction and it states that if you move a magnet through a solenoid, you would get an induced current. Say, if you have a copper solenoid, and if you want to move a magnet through it, there will be something (maybe, a force) that would prevent the magnet...
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