What is Wire: Definition and 1000 Discussions

A wire is a single usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in various standard sizes, as expressed in terms of a gauge number. The term 'wire' is also used more loosely to refer to a bundle of such strands, as in "multistranded wire", which is more correctly termed a wire rope in mechanics, or a cable in electricity.
Wire comes in solid core, stranded, or braided forms. Although usually circular in cross-section, wire can be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound coil springs, such as the Slinky toy, are made of special flattened wire.

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  1. H

    Juntion box wire optimization

    Homework Statement Two isolated farms are 12km apart on a straight country road that runs parallel to the main highway 20km away. The power company decides to run a wire from the highway to the junction box, and from there, wired of equal length to two houses. Where should the junction box...
  2. R

    Solving for Electric Field at Wire Surface: Homework Exercise

    Homework Statement A uniformly charged wire or radius R1=0.02m runs down the axis of a cylinder of inner radius R2=0.06m. The potential difference between the wire and cylinder is 60 volts. Find the electric field at the surface of the wire. Homework Equations Electric flux=Q/\epsilon0...
  3. N

    Wire connects ipod to breadboard

    Homework Statement I built an amplifier in the breadboard so I want to test it out. I know there is a type of wire that one side can connect to the ipod and the other side separate into power (red in color) and ground ( black in wire) But I forgot the name of the wire, so I want to ask if...
  4. S

    Lenz law wire and expanding loop

    Lenz law problem wire and expanding loop Homework Statement The loop has current radius R the red bar moves at velocity V. The distance the wire is from the loop is d and the top of the loop is length l Find the induced emf and the direction of the current in the loop. Homework Equations...
  5. S

    Magnetic field at a point due to a curved wire.

    Homework Statement Find the magnetic field at the point (the big dot in the picture) The curve is supposed to be a quarter circle and both wires are parallel and radius is R the wires are infinitely long Homework Equations Biot-Savart Law...
  6. T

    Applying the left/right hand rule to a wire with current

    Hi there. I'm basically trying to understand why when 2 wires are place near each other, given a current in the same direction they will attract each other. I have read a this: https://www.physicsforums.com/showthread.php?t=39472 But I don't see how some say 'generates a magnetic field...
  7. R

    A Moveable Cross wire and a Function of Time

    Homework Statement A circuit with a moveable cross wire is indicated in attached figure. The resistance is 2.5 Ω, the battery voltage is 5 V, the moveable wire length is 12 cm, and there is a uniform, constant magnetic field into the plane of the circuit (the page) with magnitude 0.3 T. (a)...
  8. E

    Wire moving at constant speed in a magnetic field

    So let's say I have a wire of length l moving in a uniform magnetic field of constant velocity. Now the induced EMF = Blv Constant velocity implies constant EMF generated per unit time. I even have a graph of EMF vs time in my textbook for such a situation showing a flat horizontal line...
  9. J

    Total energy in a wire using energy densities

    Given a cylindrical wire of radius r, length L, carrying a current I, find the total energy stored inside the wire. From griffiths, uem= εE2/2 +B2/2μ and the tot energy is ∫uem dV I have my E and B fields, but my B field is a function of x where x<r, (E is uniform) B=kx/r2...
  10. F

    Bead sliding on a rigid straight wire

    Homework Statement A bead is free to slide along a rigid, straight wire, whilst the wire is rotating at angular velocity ω about the z-axis and is tilted away from the z-axis at angle α. I have the equation of motion (EOM) and need to find an explicit solution for the distance of the bead along...
  11. T

    Line current and phase current in a 3 phase 3 wire system.

    A short question: Why and how is the line current equal to the phase current in the 3phase- 3wire system?
  12. J

    How Is the Total Energy Inside a Cylindrical Wire Calculated?

    Given a cylindrical wire of radius r, length L, carrying a current I, find the total energy stored inside the wire. From griffiths, uem= εE2/2 +B2/2μ and the tot energy is ∫uem dVI have my E and B fields, but my B field is a function of x where x<r, (E is uniform) B=kx/r2 (k=all the...
  13. B

    Ampere's Law for current carrying wire

    Homework Statement Use Ampere's Law to show that the equation for the magnetic field inside a current carrying wire is (1/2)μJr where J is the current density (assumed constant). Homework Equations ∫B*ds=μI The Attempt at a Solution ∫B*ds=μI B*ds=B(ds)cosθ I think θ...
  14. G

    Electro dynamics, E/B fields inside wire

    http://img850.imageshack.us/img850/3444/asdfga.jpg i'm used to approaching these questions by using either guass' law or amperes law but in this question i don't see how either will help since there's no enclosed charge its a current, and also since the whole wire carries the current and you...
  15. N

    Current in a wire and wire density

    Homework Statement If the current density in a wire or radius R is given by J = kr, 0 < r < R , what is the current in the wire? Homework Equations I used j = I/A, the definition of current density: current per unit cross sectional area. the formula for the area of a circle and for a...
  16. berkeman

    Why Choose a Parabolic Wire Antenna over a Solid Parabolic Antenna?

    I just saw one of these antennas, and I'm puzzled a bit by it. Why would one choose to use a parabolic wire antenna instead of a solid parabolic antenna? It would seem to be much less efficient at first glance (although I don't know if it is true or not). And how do the wire elements manage...
  17. A

    Free fall of straight wire in a homogeneous magnetic field

    hello every body. I have a high school problem a straight horizontal wire is falling freely in a homogeneous horizontal magnetic field, perpendicular to the wire and i want to find the inductive voltage. I said E= Blv=Blgt But I can also say E=ΔΦ/Δt=BΔΑ/Δt=Βl1/2gt [t][2]/Δt=1/2Blgt why...
  18. P

    Is there a solution for magnetic field interference in cables?

    Hello all, Are there any cables that are immune and not affected by magnetic fields of the strength of 1-2 Tesla? Either simple current wires, or more complex ones like USB or Ethernet cables.
  19. G

    Determine the tension in each wire?

    Homework Statement A 100kg sign is suspended by two wires with angles of 35˚ and 55˚ (to the roof) and meet at a 90˚ angle at the sign. Determine the tension in each wire. (I'm not sure if I described very well. It was on a diagram) Homework Equations Fg=mg aˆ2+bˆ2=cˆ2...
  20. M

    Why do wire-grid polarizers have a separation less than the wavelength?

    I've read about wire-grid polarizers from wikipedia. The article says that waves perpendicular to the wires cannot induce electron movement and hence they pass through with minimal energy loss. On the other hand, waves parallel to the wires are reflected by the wires because electron movement is...
  21. M

    Wire Grid Polarizers: Exploring Electron Movement

    I've read about wire-grid polarizers from wikipedia. The article says that waves perpendicular to the wires cannot induce electron movement and hence they pass through with minimal energy loss. On the other hand, waves parallel to the wires are reflected by the wires because electron movement is...
  22. C

    Modified microwave transformer- rneed advice for rectifiers and wire ratings.

    Modified microwave transformer- need advice for rectifiers and wire ratings. Hello everyone. I've been doing a lot of research as to how to go about purifying copper. There are two approaches I'm considering. Electrolysis and Smelting. The electrolysis method requires I have a DC output of low...
  23. G

    How could the frequency of a guy wire be measured?

    How to measure tension in guy wires? Could somebody please help/guide me in the right direction as to how I would go about measuring the tension in guy wires for a college assignment? I have been told that one method is to place some sort of rigid frame next to the cable, that touches the...
  24. N

    Bicycle Generator to power El Wire

    Hello, I am a new member here and am having a problem as to finding the more effective way to power my el wire. For those that don't know el wire is a thin copper wire coated in a phosphor which glows when an alternating current is applied to it. My goal is to wrap my bicycle in about 5...
  25. L

    A current-carrying circular loop placed next to a long straight wire

    Homework Statement A current-carrying circular loop of radius R is placed next to a long straight wire, as shown in the diagram below. The current in the straight wire points to the right and is of magnitude 3 A. see diagram...
  26. L

    Loop of wire is connected to the terminals of a battery

    Homework Statement A loop of wire is connected to the terminals of a battery. See Diagram: http://www.webassign.net/walker/22-35.gif The A terminal is of higher voltage, so the current travels clockwise from A to B through the loop. If you have the ability to send whatever current you like...
  27. P

    Calculating heat generated by a resistance wire

    How can I calculate how much heat a resistance wire gives off when I energize it? For example, I have calculated the wattage per square inch of a heating element I plan on building. How do I know how much actual heat it will give off? Thanks.
  28. E

    What is the force exerted by a magnetic field on a rectangular loop of wire?

    Homework Statement A rectangular loop of wire with dimensions 2.32 by 7.91 and resistance 0.557 is being pulled to the right out of a region of uniform magnetic field. The magnetic field has magnitude 3.01 and is directed into the plane of the following figure . At the instant when the...
  29. D

    Magnetic flux through coiled wire

    Homework Statement A circular coil has 25 turns and a radius of 5 cm. It is at the equator, where the earth’s magnetic field is 0.7G north. Find the magnetic flux through the coil when its plane is (a) horizontal, (b) vertical with its axis pointing north, (c) vertical with its axis pointing...
  30. C

    Describe the thermodynamic system of a wire.

    Homework Statement http://i.imgur.com/2WKCR.jpg Homework Equations Potentially: L(final) = L[1 + tau/(YA) + alpha(T - To)] The Attempt at a Solution Frankly I have no idea where to begin.
  31. T

    Finding the Force between a Straight Wire and a Triangular Current Loop

    Homework Statement A triangular loop of side length a carries a current I. If this loop is placed a distance d away from a very long straight wire carrying a current I', determine the force on the loop. See attachment for diagram. Homework Equations F=(\muII'/2\pir)L F=I'LB...
  32. D

    Force on a Magnet Moving through a Wire Loop

    Homework Statement What is the force acting on a magnetic dipole that falls through a loop of wire? Any sort of answer, exact, approximate or a reference to a source that covers this would be excellent. I haven't been able to find much of anything on this problem. Homework Equations The...
  33. B

    Net Magnetic Field at the Center of a Loop and X Distance Away From a Wire

    Homework Statement https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-prn1/553004_1959186995753_1725123128_934768_456680196_n.jpg In case the words are too small: I2= 6.61I1 The net magnetic field at center of loop is 0. I'm looking for the radius of the loop Homework Equations for...
  34. J

    Calculating Current in a Wire of Given Dimensions

    Homework Statement a wire carrying a current of 3.2A has a radius of 1.2mm. the material of the wire has 2.5x10^25 free electrons per cubic metre. the elementary charge is 1.6x10^-19 Homework Equations I=Anev cross section = pi*r^2 The Attempt at a Solution pi*0.0012^2 =...
  35. S

    How Does Resistivity Affect Copper Wire Resistance and Current Flow?

    12-gauge copper wire has a radius of 1.03×10−3 m. (a) What is the resistance of 11.5 m of this wire at 20°C. (b) How much current will pass through the wire if a potential difference of 9.00 V is applied across it? The resistivity for copper is 1.7E-8 ohm meters For part a: The equation is...
  36. S

    You have a fine wire with a cross sectional area of 9.4×10−10 m2

    You have a fine wire with a cross sectional area of 9.4×10−10 m2 and a length of 1.1 m. You wish to determine what it is made out of, so you connect it to a standard AA battery (1.5 V) and measure a current of 0.048 A. What material is the wire most likely made out of? The options for the...
  37. M

    Current carrying wire in uniform magnetic field; where is net magnetic field 0?

    Homework Statement A long wire carrying 100 A is perpendicular to the magnetic field lines of a uniform magnetic field of magnitude 5.0 mT. At what distance from the wire is the net magnetic field equal to zero? Homework Equations B = iμo/2∏R The Attempt at a Solution I...
  38. C

    Wire in E Field: Will it Deflect?

    If I had a current carrying wire in an E field. Would it deflect? The wire it self just has a B field and no free charge. But If I was moving with respect to the wire I would see length contraction and a net E field. So in my frame the wire would deflect. Or is something wrong with my reasoning?
  39. T

    Heating 800 watts nichrome wire with a battery.

    hi guys.. I'm new here and this is my first post.. my friends told me that the title of this post is impossible and i need a car battery to heat the 800W nichrome wire, and i believe them.. they also said that AC will solve the problem.. but i need to use DC so i came up with using diodes.. the...
  40. C

    Magnetic Force in a Current Carrying Wire

    Homework Statement The current in a wire consists of n electrons per unit volume moving with a velocity v. What is the effect on these electrons of the magnetic field set up by the current itself within the wire? What is the force on one electron at a distance r from the centre of the wire...
  41. S

    Inductor considered as a broken wire.

    I quote from my book: "Just after the switch is closed, the inductor acts to oppose a change in the current through it." "Because the current through each inductor is zero before the switch is closed, it will also be zero just afterward. Thus, immediately after the switch is closed, the...
  42. W

    MATLAB Creating a Basic Steer by Wire System in Simulink Matlab

    hello, i am a final year student doing electronics engineering. For my final year report i made the mistake of choosing steer by wire as a project which i really can't handle. However, i am expected just to touch the subject just on the surface. It really is a very hard topic for my level...
  43. S

    Induced emf in a solenoid from a current carrying wire nearby

    Say I have a solenoid that has a magnetic field Bo Sin(ωt) passing through its axis. What will be the EMF induced in the solenoid as a result ? I know it'll be a function of Cos (ωt) but I am more interested in how my choice of the solenoid will affect the EMF that I'll ultimately measure...
  44. I

    Components of a magnetic field in a uniform wire

    Homework Statement A straight wire, of current I, radius a is centred at (α,β). What are the x and y components of the magnetic field B inside one of the wires? Homework Equations ∮B.dl = μ I_enc ∫∫J.dS = I The Attempt at a Solution Any point (x,y) in the wire has a constant...
  45. D

    Magnetic Fields from Currents in a Wire

    Homework Statement A solid cylindrical conducting shell of inner radius a = 5.3 cm and outer radius b = 7.9 cm has its axis aligned with the z-axis as shown. It carries a uniformly distributed current I2 = 7.1 A in the positive z-direction. An infinite conducting wire is located along the...
  46. A

    Magnetic Force Experienced by a Loop of Wire

    Homework Statement The problem is shown in the link below: http://postimage.org/image/do2b7xz0b/ Homework Equations Biot-Savart Law's and dF=Idl x B The Attempt at a Solution My attempt is really just a mess. I essentially want to break it up into 2 segments. (1) Being the...
  47. S

    Making Heating Element From NiChrome Wire

    I need to make a 1 metre long heating element from NiChrome Wire. The wire I have is 0.9mm with resistance of 1.7ohms per metre. Can I wire it straight to the mains with a light dimmer switch in place to limit the power?
  48. K

    Time Dependent Current in a wire

    Homework Statement An infinite straight wire carries a current I that varies with time as shown above. It increases from 0 at t = 0 to a maximum value I1 = 2.1 A at t = t1 = 14 s, remains constant at this value until t = t2 when it decreases linearly to a value I4 = -2.1 A at t = t4 = 24 s...
  49. L

    Magnetic field along a current-carrying wire (conceptual question)?

    Homework Statement Is the magnetic field around a point in a current-carrying wire radially outward (spherically) like the electric field? Or is it a bunch of concentric circles extending in one plane? I've always thought of it as a bunch of concentric loops in the same plane, however...
  50. M

    Speed of waves in a nonuniform wire

    Homework Statement A wire that is 7.75 m long and has a uniform density of 10.0 g/cm^3 is pulled to a tension of Ft=376 N. The wire, however, does not have a uniform thickness; rather, it varies uniformly from an initial radius of 1.0 mm to a final radius of 3.3 mm where is it attached to a...
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