What is Coaxial: Definition and 188 Discussions

In geometry, coaxial means that two or more three-dimensional linear forms share a common axis. Thus, it is concentric in three-dimensional, linear forms.
A coaxial cable, as a common example, is a three-dimensional linear structure. It has a wire conductor in the centre (D), a circumferential outer conductor (B), and an insulating medium called the dielectric (C) separating these two conductors. The outer conductor is usually sheathed in a protective PVC outer jacket (A). All these have a common axis.
The dimension and material of the conductors and insulation determine the cable's characteristic impedance and attenuation at various frequencies.
In loudspeaker design, coaxial speakers are a loudspeaker system in which the individual driver units radiate sound from the same point or axis.
A coaxial weapon mount places two weapons on [roughly] the same axis – as the weapons are usually side-by-side or one on top of the other, they are technically par-axial rather than coaxial, however the distances involved mean that they are effectively coaxial as far as the operator is concerned.

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  1. E

    Electric field in a resistive, shorted coaxial cable

    Homework Statement Consider a shorted coaxial line with a resistive inner conductor with radius a, and a perfect outer conductor located at radius b. A DC voltage is applied at the input end. Find the electric and magnetic fields in the dielectric region (a<r<b), assuming the battery sets up a...
  2. F

    What is the behavior of currents on a coaxial cable?

    Hello Forum, A coaxial cable is a two conductor transmission line. If we connect a DC voltage source via a coaxial cable to a resistor so that the positive terminal is connected to the inner conductor and the negative terminal to the shield , the current will flow through the whole...
  3. G

    Capacitance per length unit of coaxial cable

    Homework Statement Coaxial cable has double layered dielectric. a=2mm, b=4mm, c=8mm, εr1=3, εr2=4.5, Uab=1000V 1. Calculate capacitance per unit length of a cable. 2. Calculate inner and outer charge densities of a cable. 2. Homework Equations Gauss law C'=Q'/U σ = nD σp = nP 3. The Attempt...
  4. fluidistic

    TM and TE waves in coaxial waveguide

    Homework Statement 1)Find the EM fields that go through a coaxial waveguide (inner radius equals a, outer radius equals b) filled with a dielectric material where both TE and TM modes propagates. 2)Find the cutoff frequency. 3)Find the cutoff frequency if we close both ends of the waveguide...
  5. C

    Maximum voltage on coaxial cable?

    Homework Statement How to determine maximum voltage that coaxial cable, whose height is L and is filled with dielectric in such way that E is the same in the dielectric and in the part of the cable that isn't filled with dielectric (only vacuum),can handle if i have maximum electric field that...
  6. R

    Finding a 1.5 GHz Line Amplifier for RG59 Coaxial Cable Loss

    Hello. I 'm looking for a line amplifier schematics working around 1.5 GHz to compensate coaxial ( RG59/CU) loss behind a L.N.A
  7. R

    Minimal Surface between two different coaxial circules

    Dear All, I am trying do find the minimal surface of revolution between two coaxial circular rings of DIFFERENT diameter. I could not find it solved in the net. So I tried to solve numerically system (13-14) Minimal Surface of Revolution -- from Wolfram MathWorld to determine "a" and "b" for...
  8. W

    Induced EMF in Coaxial Loops: Calculating Separation Distance

    1. A very large loop of metal wire with radius 1meter is driven with a linearly increasing current at a rate of 200amps/second . A very small metal wire loop with radius 5centimeter is positioned a small distance away with its center on the same axis (the loops are coaxial). The small loop...
  9. A

    E-field and charge density outside two coaxial cylinders

    I am working on a problem of electrostatics, and I am having troubles in trying to figure out one part of it. 1. Homework Statement It consists of an inner solid cylinder of radius ##a## with a voltage ##V_A##, and an outer coaxial cylindrical shell of inner radius ##b## and outer radius ##c##...
  10. 1

    Electric Field and Potential Difference in a Coaxial Cable

    Homework Statement : [/B] Co-axial cable, relative permittivity, capacitance, internal energy A long straight co-axial cable of length 1 consists of an inner conductor of radius r1 and a thin outer conductor or radius r2. The dielectric between the conductors has a relative permittivity εr...
  11. L

    Potential of coaxial with two dielectrics?

    The question asks to find the potential of the ungrounded outer conducting sheath of a coaxial cable when the inner conductor has a voltage of \frac{220}{\sqrt{3}} kV. Coaxial conditions: i) Central copper conductor of diameter 4.8 cm. ii) Insulating layer of XPLE of thickness 2.3 cm and...
  12. N

    Magnetic field for coaxial cable

    Homework Statement https://scontent-b.xx.fbcdn.net/hphotos-xpa1/v/t1.0-9/10846336_1517298108546407_4211362504714893270_n.jpg?oh=2f11c165933554a0e4003b398c877004&oe=5542789C Homework Equations ∫B⋅nda = Iencμo Ienc=∫J⋅da The Attempt at a Solution For r < a: Ienc = I...
  13. K

    Potential difference between a tube and a coaxial bar

    Homework Statement A capacitor made of a round solid bar and a thin round tube are coaxial, they are very long. the radii of the bar is ra and of the tube rb. they are both charged with λ, the charge per unit length, with opposite charges. what is the potential difference. Homework Equations...
  14. P

    What causes the magnetic field inside a coaxial cable?

    Hi. In this task we're asked to calculate the magnetic field inside the small cylinder (0>r>r1). The answer is zero, which I don't quite understand...Here is the picture: http://bildr.no/image/WTJ1VG5F.jpeg As the picture shows there's a current I going through the inner cylinder. Wouldn't this...
  15. J

    Is Coaxial Contrarotating Lift Equal to Double the Lift of Individual Blades?

    Quick question - is the lift generated by coaxial contrarotating blades equal to the lift generated by each individual lifting surface (simplified to lift x 2), or is there a more comprehensive formula available? Currently, I am using the following formula to calculate the lift of a single...
  16. R

    Proving Gradient of Electric Field in Coaxial Line Dielectric is 0

    Homework Statement Show that (Grad dot E) =0 in the dielectric of a coaxial line. (Hint: apply the divergence theorem to a portion of the dielectric.) Homework Equations Divergence theorem The Attempt at a Solution I think I need to show that grad dot E = p/epsilon = 0 I don't know - I'm...
  17. E

    Coaxial Cylinders Flow: Examining Velocity & Stress in a Rotating Fluid

    A real incompressible fluid is contained in the region between two coaxial cylinders of radii R1 and R2. The outsider cylinder rotates with angular velocity w, in stationary regime, and the flow is purely circular. Neglect the action of gravity. a) Show that vφ (azimuthal velocity component)...
  18. B

    Resonant frequency of a coaxial cable

    What is the equation (and derivation of equation) to work out the resonant frequency of a coaxial cable? Given that the cable has a resistance, capacitance and inductance per meter which are known. Links and explanations are much appreciated Thanks :smile:
  19. T

    Power transported down a coaxial cable

    Homework Statement A long coaxial cable carries current I. The current flows down the surface of the inner cylinder (of radius a) and back along the outer cylinder (of radius b). Calculate the power transported down the wire. Homework Equations The Poynting vector is given by...
  20. R

    Potential Difference between conductors for a coaxial cable, conflict

    conflicting results. find the potential between the two conductors of a coaxial cable I have already found E... E = lambda / 2 pi r epsilon my question: What are the integration limits for finding the potential between the conductors? say we have a radius a (inner conductor)...
  21. Y

    Insulation Resistance in a coaxial cable of length L

    Homework Statement Determine the insulation resistance in a coaxial cable of length L, with conductivity, as shown in Figure assume that the current density J is radial direction. The Attempt at a Solution so i was wondering if this approach is correct, consider a sequence of...
  22. Y

    Calculating Coaxial Cable Insulation Resistance for Radial Current Density

    Homework Statement Determine the insulation resistance in a coaxial cable of length L, with conductivity, as shown in Figure assume that the current density J is radial direction. The Attempt at a Solution so i was wondering if this approach is correct, consider a sequence of...
  23. X

    Length of coaxial cable, based on signal reflection

    Homework Statement We measured the time between a signal source, and it's reflection coming back through our probe after going through an open-ended coaxial cable. My teacher told us this: the cable has a polyethylene insulator between central wire and the grounding web, which has a...
  24. L

    Flux density inside and outside a coaxial cable.

    For question 4b in the problem sheet attached below, is my working correct for B outside and inside the coaxial cable? Ans: Outside coaxial:∫B.dl = μI (the integral is between 0 and 2∏r) => B = (μI)/(2∏r) Inside the coaxial: \int_{2\pi a}^{2\pi r} B.dI = μI.\frac{a^2}{\pi...
  25. U

    What is the inductance of a length l of a coaxial cable?

    A coaxial cable is modeled as a long thin cylindrical shell with radius b concentric with a solid wire of radius a (the wire is inside the shell). Calculate the inductance of a length l of this cable. (Example 32.5 Here) ---> https://echsphysics.wikispaces.com/file/view/APPhysicsCH32.pdf...
  26. N

    Calculate Coaxial Cable Loss & Input Impedance at 1 MHz

    Hey Guys, How do I work out Transmission loses and input impedance for coaxial cable? I’ve been given this website to use http://fermi.la.asu.edu/w9cf/tran/ I do have the characteristic impedance of 75Ω and frequency and I am asked to work the attenuation in dB/100ft and “input...
  27. S

    Quasi-static Approximation for coaxial wires

    Homework Statement A coaxial cable with inner radius a and outer radius b lies on the z-axis (such that the cable's axis merges with the z-axis). its length (along z-axis) is L. at z=-L there are voltage sources that are distributed uniformly connecting the inner wire to the outer one. at...
  28. L

    Attraction between coaxial solenoids

    Can anyone help me understand why two coaxial solenoids separated by a distance x, with current flowing in the same direction in each solenoid, would be attracted to each other using the right hand rule? Im sure they would be attracted to one another (with the current flowing in the same...
  29. D

    Impedance Matching Coaxial Cables

    Homework Statement We need to connect two coax cables with the same dielectric (εr = 9) but with different dimensions as shown. How big must be the radius of the outer conductor of the second line in order to match two lines? How would the velocity of the wave propagation change, if we...
  30. D

    Capacitance of Coaxial Cable Configuration with Multiple Conductors

    Homework Statement I can't seem to understand this problem (I do see that the inner cylinder and outer shell will have the same charge, but I can't see what I'm supposed to assume about the middle shell): A cable consists of three conductors, a solid inner cylinder and two thin...
  31. R

    Resistance of the insulation in coaxial cable

    Homework Statement Determine the resistance of the insulation in a length l of coaxial cable.inner radius = a and outer radius= b.Homework Equations R=\rho\frac{l}{A} Area= \pi (b^2 - a^2) The Attempt at a Solution I calculated the area between the two concentric 'circle' with radius 'a'...
  32. W

    Coaxial Cable Problem - Finding volume charge density.

    1. Homework Statement A long coaxial cable consists of an inner solid cylinder, radius a, and an outer thin coaxial cylindrical shell, radius b. The outer shell carries a uniform surface charge density σ. Find the uniform volume charge density ρ that the inner cylinder must have in order...
  33. PsychonautQQ

    Why do two opposing currents cancel each other out perfectly in Ampere's Law?

    Homework Statement http://grephysics.net/ans/9277/9 I'm confused why these two currents cancel each other out perfectly when the distance they are being measured from is closer to the outside current than the inside current... Like if the magnetic induction is proportional to the...
  34. T

    Gauss's Law and Coaxial Cables

    The diagram I've attached shows a cross-section view of a very long straight metal cylinder of radius r1 within a coaxial hollow metal cylinder of inner radius r2 and outer radius r3. The inner cylinder has a positive charge per unit length λ, whereas the outer cylinder has negative charge per...
  35. R

    Testing Book for Coaxial cable problem in Physics GRE

    Book for Coaxial cable impedance problem in Physics GRE This is GR9277, Problem 18. Is this covered in any physics undergraduate course? What subject is this problem belong to? What book do you recommend for studying this? How can I make the picture appear bigger?
  36. A

    Inductance of Solenoid on Coaxial Cable

    Homework Statement The figure below shows a short coil which is coaxial with a very long solenoid (you may approximate it as infinite.) Coil: Has 120 turns of radius 1.8 cm and resistance 5.8 . It is not attached to anything. Solenoid: Has 22700 turns/m and a radius of 1.6 cm. It receives an...
  37. P

    Find charge field within coaxial cables

    Homework Statement two very long coaxial cylinders. Inner has radius a and is solid with charge per unit length of λ. Volume is also uniform but not defined by a parameter. Outer is hollow with inner radius b and outer radius c. Outer cylinder is a conductor with charge per unit length of -2λ...
  38. U

    Mutual Inductance of coaxial coils

    Homework Statement Not sure if I'm correct or wrong..because usually M12 = M21 The Attempt at a Solution Here coil 1 and coil 2 are coaxial, with coil 2 being shorter and having smaller area.
  39. E

    Magnetic field of a Coaxial Cable

    Homework Statement A long coaxial cable consists of two concentric conductors with dimensions a = 1.20 cm, b = 5.40 cm and c = 7.30 cm. There are equal and opposite currents of 5.00 A in the conductors. Find the magnitude of the magnetic field at a distance of 0.36 cm from the center axis...
  40. G

    Calculating Bx for Two Coaxial Cylindrical Conductors

    Homework Statement Two very long coaxial cylindrical conductors are shown in cross-section above. The inner cylinder has radius a = 2 cm and caries a total current of I1 = 1.2 A in the positive z-direction (pointing out of the screen). The outer cylinder has an inner radius b = 4 cm, outer...
  41. G

    Archived Coaxial Cable With Potential Difference between conductors

    1. A coaxial cable is powering a light bulb with a steady flow of current (DC current). The electric potential difference between the outer and the inner conductor of the cable is delta V and the current flowing in the cable is I. The inner conductor's outer radius is a and the outer conductor's...
  42. DaTario

    Coaxial cables and displacement current

    Hi All, Consider a situation in which a coaxial cable have electric current i(t) = Imax * cos(w*t) flowing through its cilindrical inner cylindrical core (with radius a) and the inverse current flowing on its surface cover (with radius b). I would like to know if it is correct to say that...
  43. A

    Potential inbetween two coaxial cylinders

    Homework Statement There are 2 coaxial cylindrical conductors. The inner cylinder has radius a, while the outer cylinder has radius b. There is no charge in the region a < r < b. If the inner cylinder is at potential Vo and the outer cylinder is grounded, we want to find the potential in...
  44. R

    Calc Height Dielectric Oil Coaxial Cylinder Tubes

    Homework Statement Fromm Griffiths Two long coaxial cylindrical metal tubes (inner radius a, outer radius b) stand vertically in a tank of dielectric oil (susceptibility \chi_{epsilon}, mass density \rho. The inner one is maintained at potential V, and the outer one is grounded. To what...
  45. N

    Differential Gauss's Law & Coaxial Cable

    Homework Statement A long coaxial cable consists of an inner solid cylinder, radius a, and an outer thin coaxial cylindrical shell, radius b. The outer shell carries a uniform surface charge density σ. Find the uniform volume charge density ρ that the inner cylinder must have in order that...
  46. S

    Coaxial Power Connectors - Need help

    Hi all, I'm a mechanical engineering student and I need your help with a project as I'm somewhat not familiar to electrical stuff. I'd like to use coaxial power connectors (like the ones in laptops power input) to transmit 220 V, 15 A AC through them. The power source is fixed but the...
  47. T

    Is Cable Length a Factor in Determining Coaxial Cable's Power Rating?

    I am trying to calculate the maximum power of a coaxial cable, based on heat transfer parameters and limiting temperatures of cable components. I've determined that a certain heat load on the conductor surface (in Watts per inch of cable) will put the dielectric above its operating temperature...
  48. L

    Could a coaxial cable be used for electric current instead of radio signals?

    http://en.wikipedia.org/wiki/Coaxial_cable http://en.wikipedia.org/wiki/Poynting_vector Could a coaxial cable be used for electric current instead of radio signals? 'For example, the Poynting vector within the dielectric insulator of a coaxial cable is nearly parallel to the wire axis...
  49. C

    Calculating Magnetic Field Between Coaxial Circular Coils

    Homework Statement Two coaxial circular coils of radius R = 15 cm, each carrying 4.0 A in the same direction, are positioned a distance d = 20 cm apart, as shown in the figure. Calculate the magnitude of the magnetic field halfway between the coils along the line connecting their centers. (μ0 =...
  50. J

    How to calculate resistivity of coaxial cylinder

    Is it any model on resisivity of two tightly-attached coaxial cylinder? For example, a copper core wire is coated with layer of aluminum. How to calculate the final resistivity along axis?
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