What is Conducting wire: Definition and 30 Discussions

In electronics and electromagnetism, the electrical resistance of an object is a measure of its opposition to the flow of electric current. The reciprocal quantity is electrical conductance, and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S) (formerly called "mho"s and then represented by ℧).
The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while objects made of electrical conductors like metals tend to have very low resistance and high conductivity. This relationship is quantified by resistivity or conductivity. The nature of a material is not the only factor in resistance and conductance, however; it also depends on the size and shape of an object because these properties are extensive rather than intensive. For example, a wire's resistance is higher if it is long and thin, and lower if it is short and thick. All objects resist electrical current, except for superconductors, which have a resistance of zero.
The resistance R of an object is defined as the ratio of voltage V across it to current I through it, while the conductance G is the reciprocal:








{\displaystyle R={\frac {V}{I}},\qquad G={\frac {I}{V}}={\frac {1}{R}}}
For a wide variety of materials and conditions, V and I are directly proportional to each other, and therefore R and G are constants (although they will depend on the size and shape of the object, the material it is made of, and other factors like temperature or strain). This proportionality is called Ohm's law, and materials that satisfy it are called ohmic materials.
In other cases, such as a transformer, diode or battery, V and I are not directly proportional. The ratio V/I is sometimes still useful, and is referred to as a chordal resistance or static resistance, since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative





{\displaystyle {\frac {\mathrm {d} V}{\mathrm {d} I}}}
may be most useful; this is called the differential resistance.

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  1. L

    Conducting cable surrounded by two cylindrical shells

    What I have done: (a) If we start at ##R_5## then we have ##\Delta V=-\int_{R_5}^{R_1}\vec{E}\cdot d\vec{l}=-(\int_{R_5}^{R_4}\vec{0}\cdot d\vec{l}+\int_{R_4}^{R_3}\frac{\lambda}{\varepsilon_0}dl+\int_{R_3}^{R_2}\vec{0}\cdot d\vec{l}+\int_{R_2}^{R_1}\frac{\lambda}{\varepsilon_0}dl=-\lambda(...
  2. fluidistic

    I Energy flux direction in a conducting wire?

    On the Internet, I have read that the energy doesn't flow in the wire, for example in a very simple electric circuit made of a battery and a closed loop. When one computes the Poynting vector ##\vec S \propto \vec E \times \vec B##, one gets that its direction is towards the center of the wire...
  3. G

    Is electrocution possible from touching a conducting wire?

    why would the current flow through a person when it is already flowing through a copper conductor that is connecting the terminals.
  4. A

    Polarity of magnetic field in a conducting wire

    When current flows through a copper wire, for example, a magnetic field is produced. What is the polarity of that field? I've seen an example with special relativity and how a positive charge would be deflected. Does that mean the field is negative to a stationary object? Every video I watch...
  5. VSayantan

    Speed of a Magnet Falling through a Conducting Wire

    Homework Statement A small but very powerful bar magnet falls from rest under gravity through the center of a horizontal ring of conducting wire, as shown in the figure below (on the left). The speed-versus-time graph, in arbitrary units, of the magnet will correspond most closely to which of...
  6. B

    I Including Coulomb interaction in a free energy calculation

    Hi everyone! I am trying to create a crude electron-hopping model to study conductivity in a biological wire composed of discrete sites. The model is pretty simple: imagine a line composed of sites. Electrons can hop from site to site with probabilities that depend on the free energy difference...
  7. N

    Why a conductive shield doesn't block the magnetic field?

    Hi While studying the shielded wires, i noticed that the magnetic field of the inner conductor can penetrate the shield conductor (can be calculated in the region 3). However, the boundary condition of the magnetic field at the surface (between dielectric and perfect conductor) of a perfect...
  8. M

    Electric field inside a conducting wire

    The electric field in a 2.5mm×2.5mm square aluminum wire is 2.1×10−2 V/m . What is the current in the wire? The answer is I=4.65A. But my question is according to Gauss law, the electric field inside the conductor is zero. then how come this question says "The electric field in a 2.5mm×2.5mm...
  9. Adeel Ahmad

    Magnetic Field in a Semi-Infinite Wire

    Homework Statement Homework Equations B = μi / 4πR is the equation for a semi-infinite straight wire The Attempt at a Solution I know that for each situation in a,b, and c I would use the equation I listed above, but I am not sure what I would plug in for R for each situation.
  10. Z

    Proving an expression / help with defining electric current

    Homework Statement http://imgur.com/AotzH28 Two long, straight conducting wires with linear mass density λ are suspended from cords so that they are each horizontal, parallel to each other, and a distance d apart. The back ends of the wires are connected to each other by a slack,low-resistance...
  11. A

    Two spheres with a conducting wire

    Homework Statement 1. Two solid metal spheres are very far apart: sphere A (radius 44.1 cm) is charged to potential +2,346 Volts; sphere B (radius 63.6 cm) is charged to potential +8,848. Now, a long conducting wire connects the two spheres. When the charge has stopped moving, find the new...
  12. S

    Direction of Magnetic Field of a Parallel Conducting Wire

    Homework Statement Two long, straight, parallel wires carry currents that are directed perpendicular to the page as shown in Figure P30.9. Wire 1 carries a current I1 into the page (in the negative z direction) and passesthrough the x-axis at x a. Wire 2 passes through the x-axis at x 5 22a and...
  13. 3

    Calculating magnetic flux density using Biot-Savart law.

    Hello, all. I have been working on the following problem and was wondering if someone could check my work and provide some valuable input: Here is my work: What do you guys think about my approach to this problem?
  14. G

    Why we cannot see light from a conducting wire?

    When I connect filament(light bulb) in the electric circuit I can see the light. but when I connect only conducting wire(copper line) in the electric circuit I couldn't see the light from the conducting wire even though conducting wire less resistant than filament. How can I explain that...
  15. Hardik Batra

    Electric potential and conducting wire

    There are two sphere of radius a and b and they are connected by conducting wire. Then why the electric potential becomes same of both the sphere?
  16. andyrk

    Connecting Charged spheres by a conducting wire

    When charged spheres are connected using a conducting wire, the charge will redistribute so as to make the potential constant because the connection makes them a single conductor and conductors are equipotential surfaces. My doubt was that if the spheres are of different size and have different...
  17. N

    Magnetic field = 0 inside a conducting wire?

    Hey. If a wire is conducting electricity and all the current is concentrated at the edge of the wire, as in the skin effect, the magnetic field everywhere inside should be zero due to symmetry when applying biot-savarts law. However, according to ampere's law, it shouldn't. I take a...
  18. F

    EMF induced in conducting wire

    We just went over Faraday's law in class and our teacher stressed how a changing flux is needed to induce an emf in some coil/loop/wire. I was just wondering then, how is an emf induced in a straight conducting wire moving at a constant velocity in a constant magnetic field? It seems as if...
  19. I

    Conducting wire and moment

    Homework Statement A conducting wire runs directly over a horizontal compass in the north-south direction. When a current of magnitude I passes through the wire, the compass needle swings 20° to the west and stays in that position. When a current of 2I passes through the wire, the compass...
  20. J

    Charge seperation in a conducting wire

    If I have a conducting wire of length l and a charge separation develops between one end of the wire and the other, will the electric field have a magnitude is equal to: V/l (voltage/length of wire)??
  21. N

    Why when two conductors connected by a conducting wire gain the same potential?

    Why when two charged conductors connected by a conducting wire gain the same potential . Lets say we have two spheres of different charges why when we connect them by a single copper wire they gain the same potential Thanks in advance
  22. J

    A conducting wire has a resistivity

    Homework Statement A conducting wire has a resistivity, ρ as a function of its length, L, given by ρ=(ρ0)(L) where (ρ0) is constant. A is the cross-sectional area of the wire. the resistance of the wire would be A) [(ρ0)(L)]/A B) (ρ0)/(2A) C) [(ρ0)(L)]/(2A) D) [2(ρ0)(L^2)]/A E)...
  23. L

    Two conducting spheres connected by conducting wire.

    Homework Statement Two spherical conductors of radii r1 and r2 are separated by a distance much greater than the radius of either sphere. The spheres are connected by a conducting wire. The charges on the sphere are in equilibrium are q1 and q2 respectively, they are uniformly charged. Find...
  24. C

    A charged conducting wire in an electric field

    Suppose I have a wire with a net charge (lets say negative) in a uniform electric field from another source, such that the field lines are parallel to the wire. I want to work out the electric field surrounding the wire. Because the wire is conducting, the electric field inside the wire will...
  25. P

    Sources of Electric Field inside a conducting wire.

    Suppose that we have a wire that connects the two poles of a DC battery. The current produced indicates the presence of some Electric Field within the wire, having a constant magnitude and a direction that follows its path. Now the question is : What is the source of that Electric Field...
  26. L

    Resistance of a composite conducting wire

    1. An 80-cm-long wire is made by welding a 5.50 mm-diameter, 20-cm-long copper wire to a 5.50 mm-diameter, 60-cm-long iron wire. What is the resistance of the composite wire? 2. p = resistivity, R = pL/A 3. r = 0.001375 m goes into A = pi*r2. I used the above equation for R separately for the...
  27. C

    Conducting wire with cylindrical hole, Please help

    Homework Statement The conductor is cylindrically shaped with a radius of R. The hole on the inside is also cylindrically shaped with a radius of R/2. If a cross-section of this conductor is placed on an x-y coordinate plane, the hole would be centered on the x-axis at a distance of R/2 from...
  28. V

    Three spheres attached by conducting wire

    Homework Statement Three conducting spheres of radii a, b and c, respectively, are connected by negligibly thin conducting wires as shown in figure 4. Distances between spheres are much larger than their sizes. The electric field on the surface of the sphere of radius a is measured to be...
  29. D

    Conducting Wire Homework: Find J0 & B Inside Wire

    Homework Statement A long, straight conducting wire of radius R has a nonuniform current density J=J0*r/R, where J0 is a constant. The wire carries total current I. Find an expression for J_0 in terms of I and R. Find an expression for the magnetic field strength inside the wire at radius r...
  30. K

    How to find the electric field inside a conducting wire

    Yo, d00dz, I can't remember how to find the electric field inside a conducting wire (actually a coaxial cable) Here's the exact text of the problem: A coaxial cable (inner radius a, outer radius b) is used as a transmission line between a battery E and a resistor R, as shown in Fig 19...