What is Magnetic field: Definition and 1000 Discussions
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a magnetic field that varies with location will exert a force on a range of non-magnetic materials by affecting the motion of their outer atomic electrons. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, they are described as a map assigning a vector to each point of space or, more precisely—because of the way the magnetic field transforms under mirror reflection—as a field of pseudovectors.
In electromagnetics, the term "magnetic field" is used for two distinct but closely related vector fields denoted by the symbols B and H. In the International System of Units, H, magnetic field strength, is measured in the SI base units of ampere per meter (A/m). B, magnetic flux density, is measured in tesla (in SI base units: kilogram per second2 per ampere), which is equivalent to newton per meter per ampere. H and B differ in how they account for magnetization. In a vacuum, the two fields are related through the vacuum permeability,
B
/
μ
0
=
H
{\displaystyle \mathbf {B} /\mu _{0}=\mathbf {H} }
; but in a magnetized material, the terms differ by the material's magnetization at each point.
Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. Magnetic fields and electric fields are interrelated and are both components of the electromagnetic force, one of the four fundamental forces of nature.
Magnetic fields are used throughout modern technology, particularly in electrical engineering and electromechanics. Rotating magnetic fields are used in both electric motors and generators. The interaction of magnetic fields in electric devices such as transformers is conceptualized and investigated as magnetic circuits. Magnetic forces give information about the charge carriers in a material through the Hall effect. The Earth produces its own magnetic field, which shields the Earth's ozone layer from the solar wind and is important in navigation using a compass.
Can somebody please post the derivation of the ABC magnetic field components whose magnetic field components in the three cartesian directions(B1, B2, B3) are given by the following:
B1=A*sin(z)+C*cos(y)
B2=B*sin(x)+A*cos(z)
B3=C*sin(y)+B*cos(x)
How does plasma particles (ions, electrons, neutral particles as a whole) interact with an applied steady-state magnetic field? If you have plasma at atmospheric pressure ejected from a plasma torch in the z-axis direction (upwards/north), how will two permanent magnets, axially aligned N-S to...
I would very much appreciate a clarification on what is meant by a changing electric field in the context of statements such as 'a changing electric field creates a changing magnetic field'. My question is does the electric field actually need to reverse as a lot of examples show where two...
This has been noodling in the back of my mind ever since I read about the field strength in magnetars etc.
Magnetic fields store energy.
Magnetic fields in magnetars are inconceivably large (~10^11T).
This inconceivably large magnetic field contains ~4x10^27J/m3
From that famous guy whose...
Hello folks,
I did some research and I know a charged particle in a coil magnetic field travels along the lines of the coil.
My thoughts are having a vertical cylinder and having charged ions flow down.
1. How can I figure out how much velocity the charged ions would have.
2. Would it...
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Hello all,
Earlier today I had an electromagnetism exam, and it seems to me that this problem is unsolvable.
There's just too little information given.
A proton enters an uniform magnetic field. It's initial speed v is...
Homework Statement
A certain commercial mass spectrometer is used to separate uranium ions of mass 3.92 multiplied by 10-25 kg and charge 3.20 multiplied by 10-19 C from related species. The ions are accelerated through a potential difference of 100 kV and then pass into a uniform magnetic...
Homework Statement
charged particule reaches a uniform magnetic B field with a velocity V , and at angle theta with the magnetic field .
What is the expression of the relation , expressed as a ratio, of the radius and helical step of the trajectory of the particule .
a- 2pi/tan a
b- 2pi...
Homework Statement
a magnetic moment of U = 1 (i) + 2 (k) , surrounded by a magnetic uniform field of B= 3 (i) + 4 (j) - 1 (k)
find the potential energy in mJ ?
Homework Equations
dot product of 2 vectors
( ui*bi)+(uj*bj)+(uk*bk) =
or finding the module of both vector and doing AB...
Homework Statement
Hello, this is like an experiment of engineering.It is called a induction stove. The system consists of a bycicle, where I am going to pedal. This will turn a disk that have 20 small magnets around its circuference. Once the disk starts to turn, it will produce a constant...
Homework Statement
Consider a cylinder of thickness a=1 mm and radius R = 1 cm that is uniformly magnetized across z axis being its magnetization M= 10^5 A./m. Calculate the bound currents on the cylinder and, doing convenient approximations, the B field on the axis of the cylinder for z=0...
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...
Homework Statement
Homework EquationsThe Attempt at a Solution
The current in the inner loop should flow in anticlockwise direction so as to resist the increase in flux of the external magnetic field .
But how do I deal with the outer loop since there is smaller loop inside it ?
I think...
I know that the right hand rule applies for induced currents, and the left hand rule is for motors, but why? It doesn't seem to connect with any other physics laws and is very counter-intuitive that the current will flow in one direction rather than the opposite direction if both are...
Homework Statement
Homework EquationsThe Attempt at a Solution
I have honestly no idea about this concept . Book doesn't mention anything about this . This looks similar to Faraday cage in electrostatics . But I don't understand how this works in case of magnetic fields .
Is this related to...
Homework Statement
Homework EquationsThe Attempt at a Solution
I am having trouble interpreting the language of the problem statement . What does it mean that "half number of turns are wound " ?
When the solenoid is cut , the length becomes 1/4th of the original and number of turns also...
For a Year 12 Assignment I have to do a seminar on how magnetic fields are involved with a certain topic. I chose nuclear fusion energy production and specifically the tokamak. I understand that a toroidal magnetic field is created when a current is sent through a solenoid wrapped in a torus...
Homework Statement
A wire carrying current I=7A is shaped as half circle of radius R=0.2m.The magnetic field B(in μT) at the center is :
A)11.0(k)
B)7.9(k)
C)9.4(k)
D)6.3(k)
E)4.0(-k)
Homework Equations
B=(μ0 I)/(2πR)
The Attempt at a Solution
B = (4π*10-7 *7)/(0.2*2*π) * 0.5 (Multiply by 1/2...
Homework Statement
Homework Equations
B=(μ0*I)/(2πr)
The Attempt at a Solution
B2 = (4*4*10-7)/(2*0.1)
= 8 μT
B1 = (3*4*10-7)/(2*0.1)
= 6μT
Could I know how to determine the directions ?
I have tried looking this question up and I hope I am posting this question in the correct spot. I have read a little about photon clouds which surround electrons in a magnet but since I see myself as a very visual learner I think I am trying to think about this question as if something is...
Let's say I have a bullet flying by a magnet, the magnet will attract the bullet and change its trajectory so it will turn slightly. Does that trajectory change take energy? If it does, where does it come from? The kinetic energy of the bullet?
I've been given a question to find the magnetic flux density of the Earth if an electron is orbiting near to the surface. The answer to the question makes the magnetic force equal to the centripetal force and solves for B from there.
However, I am confused to why the gravitational force has no...
Homework Statement
A small conducting rod of length l moves with a uniform velocity v in a uniform magnetic field B. Explain how the end Y becomes positively charged.
Homework EquationsThe Attempt at a Solution
I know the concept, a force will act on the conductor which will push the...
Homework Statement
This is a multi choice question from last years aqa a level. We know a positive reading is produced on the scales indicating something is pushing down on the scales.
Please see the picture.
Homework Equations
We know current direction, not B field.
The Attempt at a...
"Calculated the total magnetic moment of a hydrogen atom in the ground state in a weak magnetic field which arises from hyper fine splitting of the ground state. How many beams does hydrogen produce from a Stern-Gerlach analyzer with a weak magnetic field?"
I've calculated the magnetic moments...
Consider that we have a magnet and a magnetometer (a fluxgate magnetometer with a single coil), standing still as shown in fig 1.
In fig 1, the magnetic field measured at the axis z1 of the magnetometer coil is B1.
But if everything (magnet, magnetometer and the axes) was rotating together...
Homework Statement
Homework EquationsThe Attempt at a Solution
To calculate magnetic field at 1 and 3 current flowing through sections A and C can be assumed as if current is flowing in a long straight wire along the dotted line . Now since the current and distances are same for 1 and 3 , B1...
Homework Statement
[/B]
There is lead XY shaped as straight wire. Next to it, circular lead with radius 0.10 m.
They are in the same plane.
XY to center of circle, O is 0.20 m.
Curent flowing through XY is 15.7 AHomework EquationsThe Attempt at a Solution
1) find magnetic field (B) at O[/B]...
If I understand it so far - a ferromagnetic object is attracted to a magnetic field ie towards the direction of most concentrated flux. So if there is no gradient there is no net force on the object.
If the flux is so strong that the object magnetically saturates, then increases in flux will...
Homework Statement
For a medium of conductivity ##\sigma##:
$$ \nabla^2 \vec{B} = \sigma \mu \mu_0 \frac{\partial \vec{B}}{\partial t} + \mu \mu_0 \epsilon \epsilon_0 \frac{\partial^2 \vec{B}}{\partial^2 t} $$
A long solenoid with ##r=b## has n turns per unit length of superconducting wire anc...
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
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...
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?
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?