# Wire Definition and 48 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. ### Potential due to a finite charged wire

Considering a reference frame with ##x=0## at the leftmost point I have for the leftmost piece of wire: ##\int_{x=0}^{x=2R}\frac{\lambda dx}{4\pi\varepsilon_0 (3R-x)}=\frac{\lambda ln(3)}{4\pi\varepsilon_0}##. The potential at O due to the semicircular piece of wire at the center is...
2. ### Confusion on the magnitude of magnetic fields

Here, the correct options are A,D. Solution: I got A as answer as ∫ B.dl=µI. But, the answer to the question says that it is a solenoid and therefore Bx=0 for point P. Here I'm a bit confused. I know this system resembles a solenoid in some ways, then By must have some finite value, but...
3. ### Origin of potentials

I think the right choice is c. I'll pass on my reasoning to you: We can think that if the formula of the potential is V(r)=\dfrac{kq}{r} If r tends to infinity, then V(r)=0. But the correct answer is d).
4. ### Calculating the flux density between two magnets

This is for an experiment to deflect a 28 SWG wire between two magnets, 3cm apart, by passing a current through it (example attached). The force on the wire is obviously F = BIL, but the wire will be passing at 1.5cm from each magnet so there will be some significant fall off of B and I can't...
5. ### Finding the diameter of a wire

Mentor node: Added code tags From=menu('select:','c', 'g', 'a', 's:'); This is part of my code and I'm not coming up with anything close l=input('input wire length') %current copper=12.5572...
6. ### I Do two perpendicular wires exert a force on each other?

I have a question for my E&M assignment (I'm not putting it in the homework thread since I just need more of a concept check) that involves a straight wire with current through it. If you have a wire with a current through it, and you have a rectangular wire also with current, to the right of...
7. ### Magnetic field created by a current carrying wire

Hi, I studied the Maxwell laws and the Biot Savart law and I found something I cannot answer. If you have a finite wire carrying current (let say 5m long) and you want to determine the magnetic induction vector due to it at some point that has distance r from the wire, you have 2 options I...
8. ### Heat loss in a conductor based on Fourier's law

Homework Statement Find the admissible current density Jadm for a wire that has no insulation and also for a wire that has two layers of insulation and compare it to Jadm for the case when the wire has only one layer of insulation. 2. The attempt at a solution and equations In the image...
9. ### Force between Parallel Current Carrying Wires

Homework Statement Two parallel wires have currents that have the same direction, but differing magnitude. The current in wire A is I, and the current in wire B is 2I. Which one of the following statements concerning the situation is true? A) Both wires attract each other with the same force...
10. ### Why the insulation rating of a wire depends on voltage?

I read online that insulation rating of the conductor depends on the voltage rating and not on the current. Can some one explain me how current doesn't contribute to insulation rating? Am i missing something? Kindly explain me
11. K

### Calculating the maximum temperature of a heating wire

<mod: moved from intro> Hello all! This is my first post in this forum. I am struggling with the following question regarding a hair dryer. The hairdryer can be seen as a cilinder with a fan inside blowing air at speeds from the table below and 1 nichrome wire which heats up consuming different...
12. M

### Flux dependant upon the number of turns?

https://atarnotes.com/forum/index.php?topic=144870.msg953546#msg953546 http://i.imgur.com/XtCj6OP.png (worked solution on left and plain answer on right; they aren't the same and neither take into account the number of turns, which adds to the confusion) Is the book's answer correct? Doesn't...
13. ### Magnetic flux between 2 parallel wires

Homework Statement Consider two long parallel wires each of radius a with a separation distance d between them. They carry current I in opposite directions. Calculate the magnetic flux through a section of length l, ignoring magnetic field inside the wires. My confusion lies in trying to...
14. ### Circular motion of an electron in a magnetic field

Imagine we take a vertical, infinite wire and we let electric current pass through. The charges create magnetic field all around the wire. Now if we introduce an electron in the magnetic field, it will have a circular motion around the wire. The Lorentz force is not conservative, this means...
15. ### Calculate the temperature of a wire as an electrical current flows through it

Hey, so I'm just wondering what are the formulas needed to calculate the temperature of a wire after x amount of time as an electrical current is passed through it. I know how to solve for it... I just forgot the formulas. Thanks
16. ### Current and resistance

Homework Statement The question wants to know why th current should be small through a wire when using an ohmmeter. Homework Equations None The Attempt at a Solution I can't think of a solution, and looking online doesn't give any answer.
17. ### Voltage between two points on an empty wire

I'm a computer science student. I'm currently learning electronics so that I can program embedded devices effectively. I'm reading from the free book at allaboutcircuits.com. Why is the voltage between two points on a wire in a closed circuit equal to zero? Note that between these two points...
18. ### Current through Thin Wires

Hey all, I've been thinking of a couple scenarios that involve thin wires (ones that have their diameter in the order of 1 mm). Suppose a gold wire with length L and diameter D is suspended straight in room temperature air and connected to some voltage V. Thus, a current will pass through the...
19. ### Finding the Magnetic Field Due to a Wire stretching from Infinity to 0

Homework Statement An intensity current I descends down the z-axis from z = \infty to z = 0, where it spreads out in an isotropic way on the plane z = 0. Compute the magnetic field. Homework Equations The only relevant equation I can think of is Ampere's Law, \oint_\gamma \vec{B} \cdot...
20. ### Motion of an electron in a nonuniform magnetic field

Homework Statement An electron is shot towards an infinitely long wire with high current flowing througuh it. Please, look at my "sketch" in the attachment. How will its trajectory be affected? What curve will it be? 2. The attempt at a solution I thought about circular motion, but the fact...
21. ### Find magnetic field at a distance from wire

Homework Statement A wire with radius R= .01 m carries a current with uniform density. At a distance r1 =1.25m from the wire, the magnetic field has a magnitude of 2.55 μT. Calculate the magnitude of the magnetic field r2=.0065m from the wire. Homework Equations B= (μ0I)/ 2πr The Attempt at...
22. ### Off center hole in a current-carrying wire - magnetic field?

Homework Statement A long copper rod 8 cm in diameter has an off-center cylindrical hole 4 cm in diameter down its full length. This conductor carries a current of 900 amps flowing in the direction “into the paper.” What is the direction, and strength in tesla, of the magnetic field at the...
23. ### Electric field in a wire with same current as another wire

Homework Statement For what electric field strength would the current in a 2.0-mm-diameter nichrome wire be the same as the current in a 1.0-mm-diameter gold wire in which the electric field strength is 0.0095 N/C? dn = .002m dg = .001m Eg = .0095 N/C ρn = 100 * 10-8 Ωm ρg = 2.44 * 10-8 Ωm...
24. ### Energy dissipated in the loop during mag. field change

Homework Statement A closed wire loop in the form of a square of side 4.0 cm is mounted with its plane horizontal. The loop has a resistance of 2.0 * 10-3 Ω, and negligible self inductance. The loop is situated in a magnetic field of strength 0.70 T directed vertically downwards. When the field...
25. ### Current induced in the loop

Homework Statement A closed wire loop in the form of a square of side 4 cm is placed with its plane perpendicular to a uniform magnetic field, which is increasing at the rate of 0.3 T s-1. The loop has negligible inductance, and a resistance of 2 * 10-3 Ω. Calculate the current induced in the...
26. ### The balance reading when direction of mag. field changes

Homework Statement The diagram shows a rigid conducting wire loop connected to a 6.0 V battery through a 6.0 V, 3.0 W lamp. The circuit is standing on a top-pan balance. A uniform horizontal magnetic field of strength 50 mT acts at right angles to the straight top part of the conducting wire in...
27. ### Multiple choice question on finding magnetic field

Homework Statement E is the "right answer" Homework Equations B around a long wire = mu * I / [2 * pi * r] The Attempt at a Solution OK. I know that the magnetic field lines will travel in a clockwise direction around the wire from the viewer's orientation with the current going away...
28. ### I Why does a kinked wire reduce data throughput?

Hi. I read that every kink in a data wire reduces throughput. What's the physical reason for this? Does the resistance of the wire increase at a kink or is this an inductive effect or something else?
29. ### Corona discharge current formula

I'm trying to find a formula for the current flowing through a wire that is only undergoing corona discharge into air. The wire is connected to a charged sphere, which provides the voltage. So far, I've just found formulas for certain ionization coefficients and electric fields, but no current...
30. ### How does charge distribute on connected conductors

This is a question that is vaguely related to coursework but is more for curiosity. Lets say there are two spheres joined by a thin wire in the presence of an electric field: Assume the conductors initially have no charge. Now I am pretty sure without the wire, the charge distribution would...
31. ### Does the length of a wire affect its resistance?

Hello, I would think that it would, because if the wire is longer there is more of a chance of their being foreign objects interfering, which could cause resistance, right? Or no?
32. ### B Methods of inducing an EMF

So from Faraday's law, a change in the magnetic flux will induce an emf on a loop of wire. { \phi }_{ B }\quad =\quad BA\\ { \varepsilon }_{ ind }\quad =\quad \frac { d{ \phi }_{ B } }{ dt } (in this case a perpendicular field) From these equations, it looks like the only way to induce a...
33. ### Biot-Savart's Law for cylindrical conductor

Homework Statement The figure shows a cross section across a diameter of a long cylindrical conductor of radius a = 2.92 cm carrying uniform current 151 A. What is the magnitude of the current's magnetic field at the center of the conductor? Homework Equations Biot-Savart's Law The Attempt...
34. ### Biot Savart Law Problem

Homework Statement The figure shows two very long straight wires (in cross section) that each carry a current of 3.19 A directly out of the page. Distance d1 = 6.00 m and distance d2 = 4.00 m. What is the magnitude of the net magnetic field at point P, which lies on a perpendicular bisector to...
35. ### Young's Modulus Question: stretch of a wire

Homework Statement A force stretches a wire by 2mm. A second wire of the same material and with the same area of cross-section and twice the length is also stretched by the same force. What will its stretch be? Homework Equations F= (YA/L)ΔL The Attempt at a Solution F, Y, and A are all...
36. ### Can copper be harvested from discarded phone wire?

I have approximately 30 pounds of discarded phone wire. I would like to recycle the metals (copper?) within, but don't know if it is feasible or even worth attempting. I also just returned from helping a parent clean out the garage, including a retired aerospace engineer's vast collection of...
37. ### Find the induction of the magnetic field at the point O

Homework Statement In a wire passes the current I=21A. A part of the wire is bent to form three consecutive sides of a square with sides 40 cm. Find the induction of the magnetic field in the point O which is the center of the square. Homework Equations B=I*μ0*/2*pi*d The Attempt at a Solution...
38. ### Tension of Suspended Cable

Homework Statement A 50.0 kg 6.00m awning is held up by a wire in the middle. A 15kg sign hangs at the end. Calculate the tension in the massless wire and the magnitude of the net force from the wall acting on the awning. The cable forms a 40 degree angle with the awning at the bottom right...
39. ### Find the force between two wires

Homework Statement Two rectilinear wires with length 100 m have the intensity 2 A. The wires in are perpendicular directions with distance 5 meters from each-other. Find the force they interact. Homework Equations F=(I1*I2*μ0*l)/(2*pi*d) The Attempt at a Solution...
40. ### Finding current and temperature of platinum wire

I plan on using a 1 ft long, 0.005" diameter platinum wire as part of an electrode. The wire will be bare but will be inside a hollow plastic tube that has an inner diameter of 0.08". It needs to be able to carry a maximum of 1 mA for a length of 10 minutes, while not exceeding 60oC. I'm not...
41. ### Wire with current and field problem

Homework Statement An electric current is uniformly distributed throughout a long, straight wire that has a diameter of 0.05m. If the current through the wire is 6.0A, calculate the magnitude of the magnetic field: a). 0.02m radially away from the wire center b). 0.05m radially away from the...
42. ### Interpreting wire type specifications on engineering drawings

I have an electrical drawing which specifies a wired connection as 3# 10+ 3# 12v- Teck symmetrical. What do all these numbers mean?
43. ### Thermal Expansion of piano wire

I'd like to setup an Excel spreadsheet to demonstrate the expected change in string frequency due to small changes in temperature. How should I go about doing this? This is the data from the piano that I can gather: -string length -string diameter -string area -string/partial frequency How do...
44. ### Frequency of a wire/spring system?

Hi, I have a wire that is fixed on one end and is under 2 lbs (approx) of tension on the other end due to a spring. Using a fixed/fixed closed form solution I found the first mode to be 73.6 Hz. In a vibration test, we found the first mode to be 110 Hz. Does this seem reasonable and where do...
45. ### Working with magnetism, solenoid

Homework Statement A bar magnet is held stationary (with respect to the loop of wire) at the centre of the loop with the North pole sticking out one end and the South pole sticking out the other. What happens to the size of any EMF induced in the loop once the magnet has been replaced by a...
46. ### How does corrosion affect the resistivity of copper wire?

I'm not sure if corrosion does have a significant effect on copper in general but if it does, how and why does it happen, and the process of it happening and its effect on the overall resistivity? This is for a physics assignment...Please help if you can. Thank you
47. ### Equilibrium Process Help

Homework Statement A 60 kg tight-rope walker carries a long beam with a mass of 30 kg across a 10 m long wire. When she is at the centre of the wire (i.e. 5 m across), each section of the wire makes an angle of 5° to the horizontal. Assuming that the mass of the wire is negligible, calculate...
48. ### Classical Hall effect when current has neutral charge

If i have a current of both negative and positive charges(i know that there is also current from only negative and only positive charges,i'm not confused) along an infinite wire of square cross-section,and the we put a homogeneous magnetic field normal to the current,then a Lorentz force acts on...