Magnetic Definition and 1000 Threads

Homework Statement This is from Griffith's Introduction to Electrodynamics, where the book is deriving the magnetic dipole moment from multipole expansion of the vector potential The vector potential of a current loop can be written as $$\mathbf{A(r)}=\frac{\mu_0 I}{4\pi} \left[ \frac{1}{r}...

Hi, I've seen many videos of neodymium magnets sliding slowly down an inclined copper plate, or slowly down a copper tube - due to eddy current braking,but never the other way around. My question is; will a copper disc sliding down an inclined magnetic plate, or down a magnetic tube act in the...

In conducting research into historical accounts of Earths magnetic field, I consistently come across proposals of stable planetary magnetic grid systems; many of these theories which have apparently been developed through much time and effort. While I am unaware of any theory that cannot be...

Homework Statement Could someone please see if my working are correct for this question, I have never actually done a question of this nature before, and after reading up about the derivation on the perturbation I thought I give ago and apply, my final answer dose not seem correct, as I believe...

Homework Statement A particle moves along a circle in a region of uniform magnetic field of magnitude B=4.0 mT. The particle is either a proton or an electron. It experiences a magnetic force of magnitude 3.2x1015 N. What are (a) the charge of the particle? (b) The particle speed? (c) The...

Homework Statement Homework EquationsThe Attempt at a Solution I am considering the two rods separately .Considering QP alone EMF induced will be (1/2)Bωl2 with Q at higher potential . Considering QR alone EMF induced will be (1/2)Bωl2 with Q at higher potential . This gives zero potential...

Is it possible that a super strong magnetic field, like those from a magnetar, could increase the instability of a radioactive atom and therefore decrease the half life? Thanks for your response in advance.

Hello, I am unable to understand a certain (important) concept. We all know what the field lines of a permanent magnet look like. They go from north to south, and curve around the magnet. This direction (direction of the magnetic field) does NOT describe the direction of a force. And that's...

Homework Statement In the central region of a solenoid that is connected to a radio frequency power source, the magnetic field oscillates at 2.5·10^6 cycles per second with an amplitude of 4 gauss. What is the amplitude of the oscillating electric field at a point 3 cm from the axis? (This...

Homework Statement Homework EquationsThe Attempt at a Solution I have already solved for the magnetic fields everywhere AND THE magnetic field at R>F = (U/2*PI*R)*(I2-I1) My only problem is i know i use the right hand rule to determine the direction of the magnetic field B as clockwise or...

Homework Statement Consider a toroidal electromagnet filled with a magnetic material of large permeability µ. The torus contains a small vacuum gap of length h. Over most of its length the torus has a circular cross section of radius R, but towards the gap the torus is tapered on both of its...

When can we use the right hand rule to find the direction of a magnetic field from current? I know that it works for an infinite wire. Does it work for a finite wire? Where does it work and not work?

Homework Statement Homework Equations Emf=B l V V is (velocity) F=QVB The Attempt at a Solution Emf=BLV Work=QBLV Force=BLV how come V=Q/m. its not possible or is it?

Homework Statement Referring to (b) in the picture above: What is the direction of the magnetic force on the electron? Homework Equations I use the right-hand rule where by putting your index finger in the direction of the magnetic field and thumb in the direction of the velocity, the middle...

I am building a magnetic suspension circuit. Basically to hold up a ball with a a piece of metal inside using a coil with an electromagnetic current. The circuit has already been set up. The ball is attracted to the coil but does not stay levitated. It should stay below the led sensor and the...

Hi, I hope that's the correct forum. So I'd like to play around with electronics and magnetism. Meaning: I'd like to build myself a electro magnet and then do some fancy stuff with it. Probably I'll try to recreate this...

Homework Statement The problem asks to find the direction of the magnetic field at point P, which is at the center of 2 separate semi-circle wires that form a circle. The current in each wire flows in the same direction (to the right). I attached a picture below. Homework EquationsThe Attempt...

I understand that magnetic flux density is measured in Teslas or Weber’s per square meter and that voltage or emf is measured using faraday’s law of induction which is E= - N dφ/dt Where N= number parallel fields Φ = magnetic flux (Wb) E= emf (V) What I don’t understand is the time function...

Homework Statement Viewers of Star Trek have heard of an antimatter drive on the Starship Enterprise. One possibility for such a futuristic energy source is to store antimatter charged particles in a vacuum chamber, circulating in a magnetic field, and then extract them as needed. Antimatter...

does the magnetic field created by AC alternate? reverse poles? if so why does a motor rotate the same way every time? does it alternate in three phase as well? thanks, if you want to direct me to literature i would appreciate that, what i have in my motors book talks about the hand rule for...

Homework Statement Example 5.9 in Griffiths's Introduction to Electrodynamics 4th shows us how to find B of a very long solenoid, consisting of n closely wound turns per unit length on a cylinder of radius R, each carrying a steady current I. In the solution, he goes on to explain why we don't...

What happens to the current through a transformer windings if the whole system is under a uniform magnetic field in the direction of the coils and with frequency equal to that of the AC in current? I think the current induced in the primary solenoid should generate a field that would make up...

Hi! I'd like to calculate the rotating magnetic field in a stator The stator is the attached picture. What I understand is the more current = the more rmf, so is there any equation / formula to calculate the rmf as a result of current? Thank you

Hey, I need a little help I know in a DC motor there are permanent magnet and also coil So my question is, what is the equation to calculate the magnetic field strength in a stator dc motor compound?

When capacitor is leaking ie, when charge is leaking or when it is discharging then will there be any magnetic field between the parallel plates of capcitor?

What is the perfect ratio of rotor pm magnetic strength:stator em magnetic strength ? What will happen if we have N52 rotor magnet surrounded by stator 187amp/turn electromagnet ? Will stator magnetic field will be sufficient for revolution of rotor??

Is correct to calculate the resistance of a semiconductor sample in a magnetic field with ohm’s law?

Homework Statement A circuit with current I has two long parallel wire sections that carry current in opposite directions. Find magneticfieldatapointPnearthesewiresthatisadistance a from one wire and b from the other wire as shown in the figure. Homework Equations B=μo*I / 2πR The Attempt...

Can anyone tell me how to determine the minimum resistance a battery needs to stop it from shorting? for example I'm making an electro magnet, with a 1.5v dc battery cell, but when i turn it on it just drains the battery.

Homework Statement Two long wires, one of which has a semicircular bend of radius R, are positioned as shown in the accompanying figure. If both wires carry a current I, how far apart must their parallel sections be so that the net magnetic field at P is zero? Does the current in the straight...

Homework Statement Homework EquationsThe Attempt at a Solution I know how to solve this problem . I just need help in interpreting the language of the problem as to what is given and what is required to calculate . 1) Is 30° the true dip and we are asked to calculate apparent dip OR 2) Is...

Homework Statement each wire carrying 10 Amps a = 0.3 meter point o located in the center Homework Equations B = permeability constant * I / ( 2 ##\pi## r) r = distance between O and the wire r perpendicular to B and I A = carrying current into the page B and C = out of the pages The...

Homework Statement A magnetic field of 0.0200 T [up] is created in a region.a) Find the initial magnetic force on an electron initially moving at 5.00 x106 m/s [N] in the field.b) What is the radius of the circular path? Make a sketch showing the path of the electron. Homework Equations...

Hi - On this forum, dgreenheck on May 20, 2013 touched on this area. I will post my question in this manner: Say one has a solenoid with a given number of turns; if the core is air, we know that if we run 10 amps through the circuit, the energy to charge a magnetic field to "B" Tesla is...

Now I know that the magnetic field is made of photons iam trying to understand how it creates the attraction of force. I am not sure if its true or not I theorized that the magnet emits photons towards the material for example Iron and it turns one end to positively charged and the other end...

Say one has a solenoid with a given number of amp-turns; if the core is air, we know that the energy to charge a magnetic field to "B" Tesla is recovered when the magnetic field collapses. Now if that core is iron instead of air, we know the magnetic field is greater than the original "B" value...

Hi, we have done an experiment where we have to measure the resistance of a sample of Ge doping-p and how it changes due to a magnetic field perpendicular to the sample with a costant current. We have found that R(B) has a quadratic trend (we have fit the dates with y = a[1+b*B^2] with a and b...

Homework Statement The question is in the attached document Homework Equations Newton's second law states that F=ma Charged particle in magnetic field experiences F=Q ( v X B) The Attempt at a Solution Since the charge 'Q' is constrained to move along a path in xy-plane in such a way that the...

Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?

Homework Statement The sun has a rotational period of 25 days. Finding the rotational period if it can shrink to form a white dwarf (##R_{WD}=10^3Km##). Knowing that the density of magnetic flux of the Sun on the surface is ##1 Gauss##, finding the magnetic flux of the white dwarf. Homework...

I know that magnets produce magnetic fields (due to internal currents within the magnet). I also know that magnetic fields cannot do work on particles. Given that, here is an apparent paradox I cannot fully understand: Consider a strong magnet and let us imagine bringing a small iron object...

When we see the aurora moving rapidly are we effectively seeing the Earths Magnetic field moving ? Is that part of the explanation for the morphology of the aurora and why they never look quite the same?

Hopefully, a simple question with a simple answer. I have a flat magnet (assume infinite long and wide) with a field strength at the surface of (for simplicity) exactly 1Tesla. What will the field strength be (in air) 1mm away from that surface? I know approximates to 1/r^3, but 1/0.001^3 =...

Hello, I have seen that biot savart's law works for infinitely narrow wires: "The formulations given above work well when the current can be approximated as running through an infinitely-narrow wire." When I wanted to derive the magnetic field of a solenoid, I had to do this substitution...

Homework Statement Calculate the time-dependent magnetic field intensity B(t) at an axial distance r from a long, thin straight copper wire that carries a sinusoidal current with an alternating frequency of 50 Hz and a maximum amplitude of 0.5 A. Homework Equations I = Asin(\omega t) B =...

Hi, Can anyone direct me to some literature that describes the numerical solution of full Maxwell's equations and Navier-Stokes equations for two-phase/multi-phase flows in coupled electric and magnetic fields. Thanks!

Homework Statement We have two very long wires, each with the same mass of 20 grams per meter. They are hung from the ceiling with two identical wires. When they both had the same current flowing to the opposite directions, they created the same angle. We double the current in one of them, is...

Homework Statement We put 2 very long parallel wires on a table, in both of them the current flows at the same direction. As a result, they get closer to each other. Does this create a conflict with the fact that magnetic force does not do work? What is the energy source for the work done on...

Thank you for reading my post. I was thinking about induced emf and magnetic flux and I realized I have a huge misunderstanding, but I don't know exactly what it is. Below I will list 4 statements which I logically know cannot all be simultaneously true. Can you please tell me which one(s) are...