Magnetism is a class of physical attributes that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomenon of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt and nickel and their alloys. The rare-earth metals neodymium and samarium are less common examples. The prefix ferro- refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4.
All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, but there are actually several types of magnetism. Paramagnetic substances, such as aluminum and oxygen, are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon, are weakly repelled; while antiferromagnetic materials, such as chromium and spin glasses, have a more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic.
The magnetic state (or magnetic phase) of a material depends on temperature, pressure, and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.
The strength of a magnetic field almost always decreases with distance, though the exact mathematical relationship between strength and distance varies. Different configurations of magnetic moments and electric currents can result in complicated magnetic fields.
Only magnetic dipoles have been observed, although some theories predict the existence of magnetic monopoles.
School physics has always taught us that the big difference between a magnetised object and an electrostatically charged object is that the latter has on it an isolated positive or negative charge whereas the former cannot be an isolated N or S pole, ie. you cannot have a magnetic monopole on a...
If an AA battery were placed in some kind of ideal conducting 'ether':
1) Would current flow, and if so, what would the flow of electrons look like?
2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like...
Homework Statement
If you were to gain a few electrons and go running in Vancouver, what would be the magnitude and direction of the magnetic force that you would experience?
Homework EquationsThe Attempt at a Solution
So I was able to determine the magnetic force but my only problem is...
Hi guys,
Non engineer here trying to understand an engineering principle. I think I must be going wrong somewhere in my thought process.
1. Faraday tells us that the EMF generated in the secondary of a transformer is equal to the change in magnetic flux divided by the change in time.
2. The...
Homework Statement
A single electron atom has the outer electron in a 4f1 excited state. Write down the orbital and spin angular momentum quantum numbers and the associated magnetic quantum numbers for this state.
Homework Equations
I don't think there is any relevant equations. I think it...
[Mod Note: Thread moved from Classical Physics, hence no formatting template]
So today we performed an experiment to measure the Earth's magnetic field in three dimensions. For one of the dimensions we got 6.6x10^-5 i
We were wondering if an imaginary magnetic field was possible and what it...
From wikipedia: "An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular; by convention, the "polarization" of electromagnetic waves refers to the direction of the electric field."
A polarizer is an object that...
So long story short, I'm trying to write a scientifically accurate short story/animation thing and it revolves around a mass driver: it's a giant and deep hole on Mars with a magnet on the bottom or sides or something and fires packets of objects to Earth at breathtaking speeds (4.66 million...
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Consider the hydrogen atom in the 42F5/2 state. Take into account the effects of finestructure (spin-orbit coupling).
(a) Write down the spectroscopic notation of the state that the 42F5/2 is degenerate with, in the absence of an external magnetic field.
(b) Calculate...
I was just in a conversation with someone regarding the magnetic field resulting outside of a solid cylinder, with a current moving down the center of the cylinder, and then the resulting magnetic field after removing the current. Now I haven't thought about magnetic fields/magnets for a while...
Hello. I am reading a paper which says that only Earth (between the rocky planets) keep a strong magnetic field and it arose an question on this:
Why does the magnetic field of the planets decrease with time in such planets?
Why the magnetic field of the Earth is the only one which keeps strong?
I would like to fine the kinetic energy of a cone that rotates around its symmetry axis.
I consider that the cone is formes by infinite cylinders with different radius and infinitesimal height. I end up with this result:
K=1/4w^2R^2hM
where w is the angular velocity R the radius h the height and...
As we know, work done by an outside agency in creating some current ''I" in an inductor 'L' is 1/2LI2. Now this result is derived by quasistatic approximation if I am not wrong. Now, I am assuming that in non quasistatic (real) scenarios, the work done by outside agency would be different(If you...
The sources I've looked at claim the magnetic field is present because there are still some electrons in the neutron star.
Here is how I understand their reasoning: a star's radius significantly decreases when it collapses into a neutron star, ultimately decreasing its moment of inertia. In...
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An infinitely long cylinder of radius R carries a "frozen-in" magnetization, parallel to the axis, ## \vec M = ks \hat z ##. There are no free currents. Find the magnetic field inside and outside the cylinder by two different methods:
(a) Locate all the bound currents and...
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Calculate the force of magnetic attraction between the northern and southern hemispheres of a uniformly charged spinning spherical shell, with radius R, angular velocity ω and surface charge density σ.
Homework Equations
Maxwell Tensor : Tm = [/B](1/μ) * ((B*n)B -...
For the Image given, i have to calculate reluctances of air gap and core which depends on respective mean path lengths.
For the left hand core, the mean path length calculated in the solution manual is 1.11 meter . However what I don't understand is that why is the length of the air gap included...
If you have uniform magnetic field, would something like a halbach array which has a non symmetrical magnetic field experience a net force? If not, is there any way to shield one side of a magnet so that it would experience a net force?
On a similar note, if you wound a wire around a sphere in...
I am putting together a hands on activity for ninth graders, which will include testing different materials to determine whether they are attracted to a magnet.
I have collected fasteners (screws, nails, bolts), and surprised that the fasteners I purchased labeled "zinc" are attracted to the...
Homework Statement
A metal rod of mass M and length L is pivoted about a hinge at point O as shown in Figure P32.80 (I have attached this to this post)
The axis of rotation passes through O into the page. Find the ratio of the maximum electric field inside the rod to the applied magnetic field...
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A short current element dl⃗ = (0.500 mm)j^ carries a current of 5.20 A in the same direction as dl⃗ . Point P is located at r⃗ = ( -0.730 m)i^+ (0.390m)k^.
Find the magnetic field at P produced by this current.
So basically what they are asking me for is the x, y, and...
Homework Statement
The Hamiltonian of a spin 1/2 particle is given by:
$$H=g\overrightarrow { S }\cdot \overrightarrow { B } $$
where ##\overrightarrow { S }=\hbar \overrightarrow{\sigma }/2## is the spin operator and ##\overrightarrow { B }## is an external magnetic field.
1. Determine...
Homework Statement
Homework EquationsThe Attempt at a Solution
Velocity of particle at any time t is
v = vxi + vyj
Net Force on the particle F = (2qvyB)i + (2qvxB)j
Net acceleration of the particle = F/m
Magnitude of net acceleration = (2qvB)/m
Particle has an initial velocity as well...
In a solenoid of N loops and uniform magnetic field B, the magnetic flux is B*N*A, where A represents the area surrounded by each loop.
I see that the N comes from the fact that you have one A for each turn, and you have N turns, so the total "area" is NA, but why do we use this? Why isn't...
My physics teacher said that the northern lights are the product of charged particles coming from the sun and interactign with our atmosphere. I believe he said that these are deflected by Earth's magnetic field and directed towards the North and South poles.
When I look at pictures on this...
Homework Statement
Homework EquationsThe Attempt at a Solution
As soon as switch S is closed , a current would flow in the circuit and the capacitor would act like a conducting wire . Force F =ilB towards right will act on the slider . There will be an acceleration but the velocity of the...
Any pure state of spin-1/2 particle can be represented by a superposition of spin up and spin-down relative to an arbitrarily direction.
lw>=a l+> + b l-> where a^2+b^2=1
If there is no magnetic field, the measurement of the spin is random and we get 50-50 chance to be spin up and spin down...
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Find the exact magnetic field a distance z above the center of a square loop of side w, carrying a current I. Verify that it reduces to the field of a dipole, with the appropriate dipole moment, when z >> w.
Homework Equations
(1) dB = μ0I/4πr2 dl × rhat
(2) r =...
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Homework EquationsThe Attempt at a Solution
Hi! I got the magnitude using F=qvB using information from the top of the qs. But the direction is confusing me. I used the Fleming's left hand rule but it sort of isn't giving me the right answer
Homework Statement
Homework Equations
The right hand curl rule gave me the counterclockwise direction for the magnetic field but I am confused about how is it going to work for the particle. Thanks
The Attempt at a Solution
Homework Statement
Hi! A long, straight, current-carrying wire is placed between a pair of magnets as shown. What is the direction of the force on the wire?
Homework Equations
Fleming's hand rules
The Attempt at a Solution
I used the Flemings right hand rule but that gives me that the force...
Hello, I have a doubt about the Complete Set of commuting observables (CSCO) in the cases when there are a magnetic field ##B## in z.
The statement is find the constant of motion and CSCO for a particle of mass m and spin 1/2, not necessary a electron or any atomic particle.
I know that the...
Homework Statement
Homework EquationsThe Attempt at a Solution
In this problem as the rod moves towards right, magnetic force of magnitude ilB starts acting towards left on the rod.This decreases the speed of the rod .The EMF induced in the rod is Blv where v is the instantaneous speed of...
I'm reading about the theory behind MRI, specifically from Farr's Physics for Medical Imaging, 2nd Edition, by Allisy-Roberts and Williams.
According to this book, the spins of the free protons in a sample line up, either parallel or antiparallel, with the externally applied magnetic field. In...
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https://imgur.com/gallery/vCOZq
Its question 26, and the figure can be seen at figure 30.26
Derive and expression for the magnetic field produced at point P due to the current carrying wire shown in figure 30.26. The curved parts of the wire are pieces of concentric...
Homework Statement
A wire 1.0 mm in diameter carries 5.0 A distributed uniformly over its cross section.
a) Find the field strength 0.10 mm from its axis.
b) Find the field strength at the wire’s surface
Homework EquationsThe Attempt at a Solution
I've used the Biot-Savart Law for a wire for...
Homework Statement
(a) What voltage will accelerate electrons to a speed of ##6.00 \times 10^{-7} m/s## ? (b) Find the radius of curvature of the path of a proton accelerated through this potential in a 0.500-T field and compare this with the radius of curvature of an electron accelerated...
Hello all; I am new in this forum, currently in High School.
For some time now, I have been looking online for a relationship between temperature and magnetic flux density of a ferromagnet; below the Curie point. However, I can't seem to find any relationship or formula. Do any of you know...
PICTURE INCLUDED
1. Homework Statement
A piece of wire is bent into an isosceles right triangle whose shorter sides have length a The wire carries current I. Calculate the magnetic field for point P. Point P is located on the Y-axis ( 0, √2a). Two corners of the triangle are are located at...
If I keep iron fillings on a cardboard with a wire carrying current in some direction, I know that the fillings will orient in concentric circles.But what happens if I keep the fillings on the underside of the cardboard? Is it possible to make them hang in the air against gravity with a...
As a SP phenomena I thought this may be the best sub to post this.
We understand how current creates a magnetic field, and almost all forms of current are really electron flow. My question is - are there any known (real world) examples of positive particle flow, creating a magnetic field...
Homework Statement
The Lorentz Force can be used to sort ions (atomic or molecular) based on their charge to mass ratio. This configuration has been used to separate isotopes and as a mass spectrometer. A beam of Strontium ions Sr+ is accelerated through a potential of 500 V and injected into...
Is it a magnetic or an electric field that causes induction in the antenna
wiki says that:
The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). enter image description here...
Homework Statement
In a homogeneous, non-magnetic, highly insulating and viscous medium, a moving particle experiences a viscous drag given by the law f→=−bv→. Here b is a positive constant. A particle having charge q is projected with an unknown velocity from a point in the medium. It almost...
Hi, initially I am aware that magnetic flux is conserved due to divergence of magnetic field is zero and for long solenoid, magnetic field inside is uniform. So magnetic field intensity (B) at point P,Q,S, T,R,U(in the attachment) must be same. But my question is : can we obtain the same...
Homework Statement
Find the magnetic moment of a crystal when placed
(i) in a weak field at high temperature
(ii) in a strong field at low temperature
Homework Equations
This is the last part of a question which I feel I have solved correctly up until this point.
The mean magnetic moment I...
I was reading the statistical physics textbook and was really confused with the notation:
I don't understand the last part of the section. Why is that \sum_{\sigma = \pm1} \sigma P(\sigma) equals to \left< \sigma \right>? And what does \left< \sigma \right> actually mean? Is it the average...
Let's consider that I have an emitter that can emit both negative and positive electric charges. Here let's consider only scenarios with two particles (one negative and one positive) that start initially at the tip of some electrode, where one or both the charges will separate from at the same...
Homework Statement
suppose we have a charging capacitor orientated along the z-axis, such that we have a changing electric field. How do I determine the direction of the associated magnetic field.
Homework EquationsThe Attempt at a Solution
I calculated the magnitude of the B field, and my...