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.
Homework Statement
This a question from an olevel paper and the marking scheme says B
I don't understand why
Homework Equations
None a theory question
The Attempt at a Solution
Aluminum and copper has less magnetic property while iron is good magnetic material. I cannot understand why the...
A long thin current-carrying conductor have a magnetic field around it in the direction according the RHR. If a compass needle was placed beside the wire it moves to point in the direction of the magnetic field. Now the current in the wire doesn't diminish and can still light a bulb in its way...
Homework Statement
A wire with a current of I (flowing into the screen) moves down on a slope.
What is the direction of the magnetic force acting on it?
Homework EquationsThe Attempt at a Solution
I have no Idea why the answer isn't horizontal, but rather opposing its velocity direction.
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...
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...
Homework Statement
There is a magnetic field B=0.02 Tesla and its direction is toward the plane (perpendicular to plane, shown by X X X X X - I'm not sure how to say this direction in English,sorry). we have a copper wire (uniform bar) perpendicular to magnetic field from south to north. we...
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 would like to receive some input about this "equation" formulated by me, a=f(i), regarding a system with a permanent magnet and an air core coil acting as an electromagnet, as described in the image:
I understand that the acceleration provided to the toy car will be a function of the...
Homework Statement
[IMG]http://[url=https://ibb.co/b3Emfo]https://preview.ibb.co/gLaEY8/20180527_055248.jpg[ A conducting bar slides down without friction on a pair of conducting rails separated by distance d. Connected to resistor R and there magnetic field B directed upward, perpendicular to...
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...
Homework Statement
A magnetic field perpendicular to the plane of a wire loop is uniform in space but changes with time tin the region of the loop. If the induced emf in the loop increases linearly with time t, then the magnitude of the magnetic field must be proportional to:
a)t^3
b)t^2...
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
So I have got the question below.
I am asked to find the phase difference between the electric field and magnetic field of electromagnetic waves traveling in a plasma, using the electrical conductivity expression.
Now I have found the frequency of the waves and I know that...
Both the gravitational and electric fields associated with matter are centered on the matter itself.
However, for a bar magnet, the magnetic field seems to be emanate from discrete loops, only part of which pass through the matter of the magnet.
What causes a magnetic field to have this...
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
Homework Equations
m=N*I*A
T=m X B
m = n(unit vector) *m
The Attempt at a Solution
To calculate m, I know it is just plugging in the information. Thus, m=0.8. Now, the question is computing the unit vector, which has me confused. Using the right hand rule, and going along...
Homework Statement
A cylinder with radius ##R## and height ##h## which has a distributed charge on its surface with density ##\sigma## spins over its axis with angular velocity ##\omega##.
If the cylinder has a mass density ##\rho##, find the relationship between magnetic momentum and angular...
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...