Wire Definition and 1000 Threads

Hi I'm thinking about making an instrument to show the force on a wire carrying electric current for students in lab. A normal wire which levitates from ground after it has current flowing in it. We have the following equations F = ILBsin(a) W = ALg 'A' being the mass of unit length of the...

Hello, I'm working on an electron gun and I am wondering if there is a way to calculate the temperature of the hot cathode, from it's thickness, resistance, the amount of current running through it, or other relevant factors. This is part of an attempt to calculate the energy of the emittted...

I'm familiar with the relationship \nabla\cdot\frac{\hat{r}}{r^2}=4\pi\delta(r) in classical electromagnetism, where \hat{r} is the separation unit vector, that is, the field vector minus the source vector. This is result can be motivated by applying the divergence theorem to a single point...

Homework Statement Homework Equations L = (N * F_b) / I (where F_b is the magnetic flux) emf = -L * (dI/dt) The Attempt at a Solution I originally thought that the inductance would decrease since it is inversely proportional to current. But, looking at the equation for emf, that would...

Homework Statement Homework Equations induced emf = - d(magnetic flux)/dt The Attempt at a Solution [/B] I believe the graph will start initially curving upwards, because it begins to cut more and more flux lines which lead to an increased induced emf. Once it is "fully" within the...

Homework Statement Homework Equations Magnetic flux = integral(B dot dA) line integral(B dot ds) = (u_o)(i_enc) (Ampere's Law) The Attempt at a Solution I can't see how Ampere's law applies because all of the magnetic field vectors along the loop will be perpendicular to that stretch of...

Can a wire be called a resistor? Also do all circuits require a resistor? If no then give an example of a circuit which doesn't have a resistor. Please thanks

When you run current through a circle formed wire it generates a magnetic field. Will this field affect the current in the wire that generates it? I mean if it does wouldn't the calculations for the created magnetic field be rather circular? The magnetic field depends on the current which in...

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...

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...

Homework Statement The problem statement is simply to find the vector potential inside and outside an infinite wire of radius R, current I and constant current density j using the Poisson equation. Homework Equations The Poisson law can be written A = μ0 /4π *∫(I/r*dl) or A = μ0 /4π *∫(i/r*dV)...

I have a 2 AMP regulated DC power supply, with variable voltage 3 - 12 v. If in a small circuit, i.e, small copper wire with 1 ohm resistor. Why am i not getting at max Amps?

Homework Statement Find the force on the triangular loop in the figure: I am trying to do this in cylindrical polar coordinates, because it builds character. Homework Equations $$\vec{B}(\vec{r}) = \frac{\mu _0}{4\pi} \int \frac{I(d\vec{l} \times \hat{\alpha})}{|\vec{\alpha}|^2}$$ Where alpha...

Homework Statement A wire along the z-axis carries a current of 6.8 A in the +z direction. Find the magnitude and direction of the force exerted on a 6.1-cm long length of the wire by a uniform magnetic field with magnitude 0.36 T in the -x direction. Homework Equations F=I(LxB) The Attempt...

I'm new here, and I hope I'm posting this in the right place. My colleagues and I are trying to take the temperature of a steel wire as it's heated. We're heating it by putting a current through it. The problem we're encountering is that the thermocouple we're using to take the temperature of...

A piece of wire is cut into two pieces. Each piece is then bent to form a square. If the sum of the areas of the two squares is 5L^2/128, how long is each piece of the wire? My Reasoning: I see the words square and sum of the squares. A = s^2, where s is side of the square. Sum of the areas...

It's been like 3 or 4 years since I've built an electric motor & I've forgotten mostly everything and need some help getting this worked out for those that don't mind. I'm trying to build a 48V 40-60A eBike motor. I'm using 200C 10AWG Magnet Wire. I have a 24 pole stator core. The stator core...

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

I am first time using a contactor. I have a 3-phase contactor with me, Need to switch on and off without any load connected. It has two auxiliary terminals A1 and A2, for just to turn on how it should be connected?

When winding a coil around a magnetic core, if you wanted to tap the coil such that each half has the same AC voltage output, would you: A) wind each part at the same RPM for the same amount of time, to get the same number of turns for each, or B) wind the second part proportionally less, to...

Hi all, the question is in regards to magnetic fields in a wire. Please refer to illustration below to understand my question. (https://www.imageupload.co.uk/image/B9f1) As you can see in Picture 3 two wires parallel to each other will attract each other if the current is going in the same...

Hello Physics Forums users, Thank you for taking the time to read my thread. I has just reading through this following article: http://www.sciencehq.com/physics/electromagnetic-induction.html when I came across this: And became rather confused. The right hand rule dictates that in this...

Hey everybody, So I've decided to try and make a copper wire magnet generator (real small) for part of my senior design project. If I can get this to work I can potentially reduce my fixture significantly. Anyways, I purchased some real small wind turbine generators off the shelf to play with...

Homework Statement Homework EquationsThe Attempt at a Solution I attempted all of the parts: I think I did the right things for a-b-c-d, but I am pretty unsure about e & f. Can someone verify if my logic is right? Thanks.

Homework Statement Find the electric field a distance ##z## above center of a square loop of wire,each of whose sides has length ##l## and uniform charge per length ##λ## Homework Equations ##dE=\frac {1} {4πε_0} dq \frac {1} {r^2}## (magnitude) The Attempt at a Solution...

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.

Maybe there's a tiny battery somewhere, just to make it realistic. The wire is also very thin, and thus needs little to no force to be bent. What happens to the wire? Does it twist on itself because each piece of the wire experiences a Lorentz force due to the magnetic field of the wire on the...

Basically I'm not sure how the interaction between the circular magnetic field produced by the current in the wire and the magnetic field of the permanent magnet interact to cause the wire to move in circular motion. If someone could explain that I would appreciate it.

im doing some personal research into building my own generator. i am looking for info on how wire diameter affects the power produced by the generator. specificaly: what AWG of wire is best for coils that are being used to generate as clost to the statdard killowatt/hour as possible.

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...

Hey guys! Any answers will be much appreciated! The following is a deep conceptual issue I have. The diagram is a bit crude but will suffice I think. Note: Had drawn the circular 'electric field' at the time, to just help myself over my confusion. Feel free to ignore it. As per Ohm's law V...

Homework Statement An infinite line charge (wire) has lambda = lambda0. It produces an electric field of magnitude 5E4 N/C at a distance of 2m. Determine the typical force between two adjacent extra electrons in the wireHomework Equations E_line = lambda/(2pi*r*epsilon0) The Attempt at a...

Homework Statement An office worker uses an immersion heater to warm 250 g of water in a light, covered, insulated cup from 20 degrees C to 100 degrees C in 4 minutes. The heater is Nichrome resistance wire connected to 120V power supply. Assume wire is at 100 degree C during 4 minute time...

Homework Statement A 10 kg load suspended by a brass wire 10 m long is observed to vibrate vertically in SHM at a frequency of 10 vib/s. Given that the Young's modulus for brass is , what is the cross-sectional area of the wire? So we know: m = 10kg l = 10m f = 10Hz Y = 9x10^10 Homework...

Homework Statement Hi everybody! I have the following problem to solve: An infinitely long and thin straight wire carries a constant charge density ##\lambda## and moves at a constant relativistic speed ##\vec{v}## perpendicularly (##\beta##) and parallel (##\alpha##) to its axis. a)...

In my textbook it says:"in the hot-wire ammeter the pointer stands at a definite reading when the temperature of platinum-iridium becomes constant and the wire stops expanding. That is achieved when the rate of heat radiated by the platinum-iridium wire becomes equal to the rate of heat...

Homework Statement Homework EquationsThe Attempt at a Solution Current is I = nqvA so drift velocity V is: V = I/nqA Drift velocity for x is: Vx = I/nqA Drift velocity for y is: Vy = 2I/nqA So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)

Homework Statement Homework EquationsThe Attempt at a Solution I know I = nqvA When the pd is applied the surface that is 8cm long, the cross sectional area is 32cm (8x4) but when the pd is applied across the 4cm side, the cross sectional area is now 16cm (4x4) so I has decreased by a...

Homework Statement A long round wire of radius a and conductivity σ is coated with a material of conductivity 0.1σ. (a) What must be the thickness of the coating so that the resistance per unit length of the uncoated wire is reduced by 50%? 2. Homework Equations [/B] R = l/(σS) where R is the...

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...

Hi, Consider a wire with a pulsating DC current next to another wire. The expanding and contraction magnetic field induces a current into the second wire. Consider the same but in the second case we have a metal chassis. I assume the same magnetic field is inducing a current into the chassis...

The induced emf in a straight wire is determined by the equation (emf=Blv sinθ) where θ is the angle between the direction of the motion and the lines of the magnetic field, and frequently, I see diagrams like these explaining the phenomenon: In those pictures the wire is perpendicular to the...

I am planning to build a foam cutter by heating up a piece of nichrome wire. I found that nichrome has a relatively high resistance compared to other conductors and it is the reason why it is used as a heating element. That is what confuses me because I think it only applies for constant voltage...

i connected one probe of digital mutimeter to the Earth terminal of domestic ac supply and held the other probe. it showed resistance of 1.8Mohm . but when i touched that end (one i'd held) to the floor. it displays 1( beyond 200Mohm ). why so ? shouldn't resistance be lesser?doesnt any current...

So here is the problem, it asks me to find the total magnetic field on BA, i made a vectorial sum with the magnetic field generated by i1 and by i2 and i got the right result, but why not adding also the magnetic field generated by the wire itself? I mean generated by CD why isn't that correct...

Homework Statement The spoke of a wire wheel is 9.5 cm long, 3.5 mm in diameter, and under tension of 2100 N. The wire is made of steel of density 7860 kg/m3. When struck with a metal tool at its center, the spoke rings at its fundamental frequency. What is that frequency? Homework Equations...

Hi everyone, I am part of a senior design group that is building a dynonameter to test shocks. We are ordering parts tomorrow morning and so I want to make sure that I am not missing anything. I do not have any experience with VFD's or three phase motors but I am doing my best to research and...

Not sure if I posted it here or elsewhere. I made a Nixie clock controlled with an Arduino. To make it possible to set the clock I have added a button connected with a wire. Pressed button generates an interrupt which I use to "round" the clock up or down to a full minute. The button has a...

Hi My question is about magnetic field I mean I know where their formulas are derived from amperes law but I didnt really understand why and how there's is a difference in magnetic fields outside and inside a crrent carrying wire the field inside a current carrying wire is B = μoIr^2/2πR^2 the...

I'm trying to resolve an issue I'm experiencing with some overhead power distribution lines, was wondering if anyone can help me out. Here is the scenario: three phase, 4 wire, wye connected 13.4kV power distribution system. 556.5kcmil bare ACRS wire is mounted on a crossarm 24" apart over a...