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. B

    Magnetic field of a solenoid problem

    A solenoid of radius 0.0523m is made of a long piece of wire of radius 0.002432m, length 54.0m, and resistivity 7.4x10^-9 \Omegam. The solenoid is closely wound with a single wire thickness. The permeability of free space is 1.25664x10^-6 Tm/A. Find the magnetic field at the center of the...
  2. P

    Magnetic field in a solenoid - -

    Homework Statement 6. A solenoid 25.0 cm long with a cross-sectional area of 0.500 cm2 has 400 turns of wire and carries a current of 80.0 A. Calculate: a) the magnetic field in the solenoid; b) the energy density in the magnetic field if the solenoid is filled with air. (2 marks)...
  3. A

    Solenoid homework question

    How many turns of wire would be on a solenoid carrying a current 4.9 A if the solenoid is 17 cm in diameter, 248 cm long, and the field at the center is 2.9 × 10-3 T? I can't seem to get the right answer... I plug the values into B=n*u0*I and then solve for N. I know that n=N/length
  4. N

    Current flowing in square loop of wire surrounds a solenoid?

    Homework Statement A square loop of wire surrounds a solenoid. The side of the square is 0.1 m, while the radius of the solenoid is 0.025 m. The square loop has a resistance of 30 W. The solenoid has 500 turns and is 0.3 m long. The current in the solenoid is increasing at a constant rate of...
  5. J

    What is the mangitude field inside the inner solenoid?

    Homework Statement 1. Homework Statement A 20cm long solenoid has 4000 turns of wire. Insiude this solenoid is a second on, also 20cmlong but with 2500 turns of wire. If a 2.5 A current flows in each solenoid in the same directon, what is the magnetic field inside the inner solenoid...
  6. J

    Finding the magnetic field inside the inner solenoid

    Homework Statement A 20cm long solenoid has 4000 turns of wire. Insiude this solenoid is a second on, also 20cmlong but with 2500 turns of wire. If a 2.5 A current flows in each solenoid in the same directon, what is the magnetic field inside the inner solenoid? Homework Equations...
  7. S

    What causes the voltage drop across a solenoid?

    We are currently learning about solenoids in my physics class, and am very confused about where this potential drop comes from across a solenoid. I understand that an opposing electric field is created when a switch is first opened because of Faradays Law and the fact that the magnetic flux...
  8. J

    Solenoid Circuit: Understanding Needle Direction with Open and Closed Switch

    Homework Statement A soft iron bar in a solenoid is placed in a circuit. There are two compasses, 1 is on the West side of the iron bar and the other is to the North. The circuit switch is open, which way will be compass needles be pointing? Which way will the compass needles be pointing if...
  9. N

    Copper Pipe in Solenoid Center

    I wanted to know how the magnetic field of a solenoid would be affected if a copper/iron pipe section was put into its center. In other words, what would the resulting magnetic field be if I simply wrapped a coil around a metal pipe section without removing the pipe afterward? Will there be...
  10. C

    Loop around an infinite solenoid?

    Say I have an ideal (long and tightly wound) solenoid, and I put a ring of wire around it (large ring). Then, by Faraday's law, if I put a current through the solenoid there will be an induced current in the wire ring around the solenoid. But if there are no B-field lines crossing my ring of...
  11. J

    Calculating Current for 1.5T in Solenoid

    Homework Statement Solenoid is 1.8m long and 75 cm in diam. one layer tightly wound with wire that has diam 2mm. what current needs to run thru to get 1.5T Homework Equations N=2piR/(L) where R is radius of solenoid and L is wire lenght The Attempt at a Solution Once I find how...
  12. P

    What is the Optimal Wire Spacing for a Strong Magnetic Field in a Solenoid?

    Homework Statement You have 12m of 0.50mm diameter copper wire and a power supply capable of passing 17A through the wire. What magnetic field strength would you obtain inside a 2.0-mm-diameter solenoid with the wire spaced as closely as possible? Homework Equations The Attempt...
  13. P

    Solenoid Magnetic Field Help

    Homework Statement You have 12m of 0.50mm diameter copper wire and a power supply capable of passing 17A through the wire. a)What magnetic field strength would you obtain inside a 2.0cm diameter solenoid with the wire spaced as closely as possible? b)What magnetic field strength would you...
  14. P

    Solenoid Magnetic Field wire spacing Help

    Homework Statement You have 12m of 0.50mm diameter copper wire and a power supply capable of passing 17A through the wire. What magnetic field strength would you obtain inside a 2.0cm diameter solenoid with the wire spaced as closely as possible?Homework Equations B=u0nIThe Attempt at a...
  15. R

    How do you calculate magnetic field stregth outside a solenoid?

    Hi, I've have been searching for help in calculating the magnetic field strength at any given position outside a solenoid. I can use Biot-Savart's to get the field along the axis of the solenoid but how does the field vary perpendicular to the axis of the solenoid, for example. Rob
  16. H

    Inductance of a straight vs toroidal solenoid

    According to widely known formulas, the inductance of a long straight solenoid will remain practically the same if we bend it into a toroidal solenoid. It seems to be a contradiction, because the magnetic path length of a straight solenoid is more than two times greater.
  17. P

    Electrical energy stored in solenoid

    I have a solenoid which has a current passing through it which increases linearly with time. I have proved that the energy stored in the magnetic field is equal to the energy being pumped in according to the surface integral of the poynting vector. This implies the energy stored in the electric...
  18. A

    Varying inductance of solenoid

    Can anyone explain the concept behind changing of inductance of a solenoid (when AC current is passing through solenoid) on moving a metal sleeve (hollow metallic pipe) over the solenoid enclosing the solenoid.
  19. M

    Iron Core Solenoids: Proportions & Magnetic Field Effects

    Hi, I've been trying to learn about iron core solenoids and I'm having trouble finding information on a concept (probably obvious but I'm new to this). I've been looking at the equations for iron core solenoids online, and it's alluded to that these equations only hold true when the proportion...
  20. E

    Magnetic Field on an Axial point within a Solenoid

    Homework Statement Thin Shell Solenoid Homework Equations General Case Formula Found: http://www.netdenizen.com/emagnet/solenoids/thinsolenoid.htm" The Attempt at a Solutionplugged in variables and got .00062919475 T 4 other attempts were made using trivial solutions. Even tried finding...
  21. C

    How to Build a Foot-Actuated Solenoid System for Pushbutton Switches

    I have a toy that is mounted 4 feet above the floor on which there are 3 pushbutton DSTP switches that I would like to actuate intermittently with my feet. I believe that I can do this by building a device that pairs 3 appropriately positioned solenoids with 3 momentary SPDT footswitches all...
  22. R

    How to Make a Solenoid: Steps & Materials

    Dear all I just joint with the group, I want to make solenoid self. I need plunger moving more 100 times/s, with strong force. anyone can help me to make this solenoid? and what material are suitable to make it? thanks for attention
  23. M

    Solenoid Valves, fluid through Nozzle - not closing

    Hello I have a problem that I can't understand... I am putting kerosene pressurised to 160psi through a 1/4" BSP solenoid with 13mm orifice. On the out port of the solenoid is a 1/4" BSP to 2mm ID nozzle. The idea is it sprays out a stream of kerosene. The kerosene is provided by...
  24. H

    Force generated by a solenoid

    Homework Statement I am building a coil gun with a single solenoid. I am going through the equations I know for magnetic force and others but I don't know if I am finding the force the wire feels or if it will be the force the projectile undergoes. Homework Equations F=qvB (assuming...
  25. L

    Bar magnet entering a solenoid

    I've attached a diagram of a bar magnet being plunged into a solenoid. I'd like someone to explain the direction of the current please. Why do both arrows indicating current move upwards? Using the right hand grip rule i understand the north pole being in the position it's in. I get a...
  26. L

    Current needed through solenoid to produce given B field

    1. Magnetic resonance imaging needs a magnetic field strength of 1.5 T. The solenoid is 1.8 m long and 75 cm in diameter. It is tightly wound with a single layer of 2.20-mm-diameter superconducting wire. 2. B = mu0BI / l 3. Is there a way to do this without finding N? Either way...
  27. K

    Coil length or Solenoid length?

    This is not a homework. I am just pretty confused about a problem (with solution!) I saw in the internet found here: http://www.transtutors.com/physics-homework-help/electromagnetism/Electromagnetic-induction.aspx The part I am confused is the mutual inductance part. Here I repeat the question...
  28. S

    Solenoid Passing through square coil-Finding electric field

    Solenoid Passing through square coil--Finding electric field Homework Statement A very long solenoid with n turns of wire per unit length and radius b carries a current I(t) which decays with time as I(t)=I0e-t/T. The direction of current in the solenoid is as shown below. The solenoid passes...
  29. D

    How to Calculate the Length of Wire Needed for a Solenoid?

    Homework Statement A solenoid is designed to produce a magnetic field of 2.2 * 10^-2 t its center. It has a radius of 1.6 cm and a length of 44 cm, and the wire can carry a max current of 13 A. The first question was what minimum number of turns per unit length must the solenoid have...
  30. L

    Energy stored and # turns in an MRI machine (solenoid)

    1. MRI (magnetic resonance imaging) is a medical technique that produces detailed "pictures" of the interior of the body. The patient is placed into a solenoid that is 40 cm in diameter and 1.0 m long. A 100 A current creates a 5.0 T magnetic field inside the solenoid. To carry such a large...
  31. L

    Current as a function of time in a solenoid

    1. The figure shows a five-turn, 1.0-cm-diameter coil with R = 0.20 ohms inside a 2.0-cm-diameter solenoid. The solenoid is 9.0 cm long, has 130 turns, and carries the current shown in the graph. A positive current is cw when seen from the left. Determine the current in the coil at =...
  32. M

    Vector Potential of Long Solenoid

    Let me preface by saying that I am a freshman in an introductory level Electricity and Magnetism course. My professor has assigned this problem, as he briefly introduced the idea of vector potentials, along with curl and divergence operators. I am VERY much lacking in knowledge of any of these...
  33. A

    Maximize the magnetic field in a solenoid

    Homework Statement Assuming we have equal volumes in both scenarios, which would maximize the magnetic field in a solenoid: a thick and short wire or a thin and long wire. Homework Equations B=(m)(constant)(I)/(2R) m= the number of layers of wireThe Attempt at a Solution The answer is clearly...
  34. Q

    Magnetic flux through a solenoid

    ok, the magnetic field through a single ring is n\muI , so the flux is BAcos(theta), with cos(theta)=1, flux = BA = piR2n\muI so why for the entire solenoid flux, it is now nL*the flux above? where L = length of solenoid shouldn't multiplying it with just n = number of rings be suffice...
  35. A

    Proving turns per length on a solenoid

    Homework Statement Prove that the number of turns per length on a solenoid is equal to 1/(diameter). Homework Equations A= 2(pi)(R) The Attempt at a Solution number of turns= length/(2pi*radius) number of coils per length=(length/(2pi*radius))/length number of coils per...
  36. P

    Magnetic force on sides of square solenoid

    Homework Statement A square 5-turn coil with sides .03 m long and carrying 2 A of current is placed in a uniform magnetic field of .07 T, as shown. What is the magnitude and direction of the force on each of the four sides? What is the magnitude and direction of the torque \tau on the...
  37. S

    Calculating Magnetic Flux from a Solenoid with Given Parameters

    Homework Statement A solenoid 2.50 cm in diameter and 26.0 cm long has 285 turns and carries 12.0 A. (a) Calculate the flux through the surface of a disk of radius 5.00 cm that is positioned perpendicular to and centered on the axis of the solenoid, as in Figure P30.36a. (b) Figure P30.36b...
  38. N

    Exploring Effects of an External Magnetic Field on Solenoid Performance

    I was wondering, are there significant effects on the performance of a solenoid when the solenoid is inside an external magnetic field? Does it affect the rate at which the magnetic field is established within the solenoid?
  39. A

    I Would like to know , it is about solenoid

    Hi, is there any rule that we can use to find the The length of a solenoid in the magnetic field Questions??
  40. M

    Mutual Inductance in a solenoid

    Homework Statement A long solenoid (black coil) with cross-sectional area A cm^2 and length L is wound with n1 turns of wire. A time-varying current i1 flows through this wire. A shorter coil (blue coil) with n2 turns of wire surrounds it. Use (uo)(m*kg/s^2*A^2) 1) Find the value M of the...
  41. M

    Determine inductance of a solenoid

    Homework Statement Determine the inductance of a solenoid with 650 turns in a length of 21 cm. The circular cross section of the solenoid has a radius of 4.2 cm. Homework Equations ? The Attempt at a Solution I've looked all over my textbook and can't come up with a possible...
  42. A

    Calculating Torque on Magnet in Solenoid

    I am a mechanical engineer and am having to do some calculations concerning magnets and solenoids for a project I am on. I have a solenoid (defined by number loops, current and cross sectional area). Inside the solenoid is a rare Earth bar magnet of some length, initial mis alignment...
  43. Pengwuino

    Quasi-stastic solenoid magnetic field

    The construction of and excitation of an infinite, straight, right circular solenoid of radius a, with N turns per unit length, are such taht tis current I(t) is the same everywehre along its length and is changed very slowly in time. Show that the fields far from the solenoid are approximately...
  44. G

    Square loop of wire surrounding a solenoid

    A square loop of wire surrounds a solenoid. The side of the square is 0.1 m, while the radius of the solenoid is 0.025 m. The square loop has a resistance of 30 W. The solenoid has 500 turns and is 0.3 m long. The current in the solenoid is increasing at a constant rate of 0.7 A/s. What is the...
  45. K

    Magnetic flux through the circular cross-sectional area of the solenoid

    Homework Statement A solenoid 1.7 cm in diameter and 30 cm in length has 4000 turns and carries a current of 5 A. Calculate the magnetic flux(in Wb) through the circular cross-sectional area of the solenoid. Since this is a very long solenoid, you may use the simplified magnetic field formula...
  46. Z

    Force On Rod Inserted In Solenoid

    Homework Statement A long cylindrical rod (permeability u , length L0, radius R) is partially inserted into a long solenoid (length L1, radius R, turn density n, and fixed current I) How large is the force on the rod? Our hint is to first calculate the total energy in the field...
  47. B

    Magnetic Circuit Problem Involving a Solenoid and Plunger

    Homework Statement The problem can be found http://whites.sdsmt.edu/classes/ee382/homework/382Homework1.pdf" (the last one), along with a picture of the circuit. Homework Equations R = l/(µS) mmf = NI = ΨR B = Ψ/S The Attempt at a Solution I've never done a problem like this...
  48. M

    Calculating the mass in a solenoid system

    Homework Statement Through the bigger coil with N = 10,000 turns of wire and length of L = 30 cm is flowing electric current of I = 5 A. Inside the big coil we insert a smaller coil with N(1) = 500 turns, length of L(1) = 3 cm, and a radius r = 1 cm. The electric current flowing through the...
  49. J

    Applying amperes law and faradays law to a solenoid and energy density

    This isn't really a homework problem, I just need to know how to do a problem similar to this one for the final and I don't want to fail, so I posted it here. A solenoid with n turns per unit length, length l and radius a (l>>a) has a current I(t)==Io sin(wt) [w is omega], where I and w are...
  50. G

    What is the most effective design for a coil gun?

    Im in the process of making a coil gun and I need to do some calculations but I am not sure how to get the Force of the magnetic field. I know how to claculate the field and I have the values of my capacitors that I will be using to discharge the current into the magnetic wire. Can someone...
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