A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.
A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.
Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.
An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops. Often, the coil is wrapped around a core of "soft" ferromagnetic material such as mild steel, which greatly enhances the magnetic field produced by the coil.
this video ( ) demonstrates lenz's law, if the current produced by the magnet fall induces an opposing magnetic field , after many tries , can this field demagnetize the magnet , another thing, consider this : if the copper pipe was instead a pvc pipe, and i wrapped around it copper wires , so...
Hey guys. I'm building a mini electric generator and I would like some clarification on Faraday's Law.
So his law states that:
V=-N*(ΔBA)/(Δt)
Where voltage generated equals the number of turns times the negative rate of magnetic flux.
So my question regards the number of turns part...
Hello Friends
I am working on home made electromagnet and I have only volt & Ohms details like 12Volt DC, 24Volt DC & 240V AC and ohms is 80Ω, 100Ω & 120Ω for all for example 12VDC 80 ohms coil, 12VDC 100ohms,24VDC 80Ohms coil...etc.
now i want to know which copper gauge we have to choose...
I just found out today that this is a real thing, people can get a tiny neodymium magnet implanted into your finger tip and apparently it allows you to feel the electromagnetic field, and the strength varies depending on where you are and what your hands are close to.
I just wondered what...
Gentlemen, the the image shows 2 N48 neodymium magnets of the same volume 54 in2. On several website I can use magnetic flux density calculators to get the Br of the rectangular magnetic but haven't found one that calculates the value of the arc magnet. The Br value of the rectangular magnet is...
Hi my name is HopelesslyFaithful (HF) (forum didn't allow all chars). I am from Notebookreview and while googling for my project. I came across this site a thread that was helpful but also made more questions. I posted this on NBR so i did a direct copy paste hoping i could get some expert help...
Hello Physics Forums World
this is my first post so please be gentle.
I am working on a project and wanted to understand the strength of magnets over distance.
Imagine, if you will, two magnets both with a gauss of 3600, the opposite poles are facing each other. how would I calculate...
A magnet only attract ferromagnetic material because they have magnetic domains which will align to form magnetic dipole when external magnetic field applied.
Paramagnet don't have domains. Due to the presence of some unpaired electron, they will cause the realignment of the electron path when...
Hi,
I am trying to create a hall effect based position sensor to be attached onto a DC motor to generate feedback for position control. I am thinking of the following arrangement:
4 hall sensors are placed 90 degrees apart around the magnetic element. Each sensor surface is directed at the...
Homework Statement
When putting a magnet into a solenoid, under what conditions is a current generated?
The Attempt at a Solution
In order for a current to be generated, the magnet needed to be moving as it passed through the solenoid. This is due to Faraday’s law, which states that an...
We just started magneto statics in school and were told about the use of magnetic monopoles for problem-solving reasons. So we were told that the magnetic length of a bar magnet differs from its geometrical length. I can't quite seem to figure out why we can't assume the monopoles to be right at...
OK... so my understanding is that a DC generator under no load generates high voltages without any current, but does the same hold true for an AC alternator?
What happens with current when the RPMs of the alternator exceed what is necessary for the current requirements?
What is "magnet wire"?
I have a test procedure I am trying to follow and it calls for "two strands of twisted magnet wire." I know it is referring to something like this:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHZW4&P=FR
I know the transmission line characteristics of twisted...
Magnet Phenomenon: The "divergent" region of a ring magnet
Here's a puzzler:
I have a NdFeB ring magnet, 1.75" outer diameter x 1.375" inner diameter x 0.25" thick, N40 grade. It is axially magnetized so that the north pole is toward one face and the south pole is toward the opposite face. The...
Hey guys.
I was just wondering about Mu-Metal.
I'm sure you guys know what a Magnet "Keeper" is.
If I was to take a thick piece of Mu-Metal and lay it across a magnet from the North to the South pole, would this act as a Keeper?
I'm trying to reduce the amount of flux loss over time...
Hello all,
I am a newbie here but have a question that I was hoping someone could answer. Would a permanent magnet give off a single frequency or would it give off a spectrum of frequencies, like an incadescent light bulb can give off a spectrum of frequencies? I can measure the intensity...
Permanent magnet can degenerate by many ways. But it really needed in compact generator to convert mechanical force into electric
But are there any other way to generate electric from mechanical force without magnet?
I want to design self exited magnet for dynamo. It need tobe an effect that...
I have a bit of a theoretical question. If one has a current carrying wire in a magnetic field such as in an electric motor rotor, does the resulting force on the wire also impart an opposing force on the stator magnets which are producing the magnetic field as Newton’s third law says? Also, if...
A mechanical design question, just wanted to pick your brains about a project I'm working on.
I have a fixture that houses a magnet, when an operator loads a part with a screw the magnet jumps and a thru beam on the magnet detects that a screw is present. Without a screw (below) the magnet...
I'm trashing the template here because I'm not looking for help with how to solve my homework problem. Instead, I'm looking for what my question actually means!
I'm given an equation that describes a magnetic field. One of the specs I'm given is that the magnet period is 10cm. What in the...
Let's say you have a strong spherical neodymium magnet (for the purposes of this example, let's give it a 1 cm diameter), and you were to place it on a machine which rapidly rotates the magnet. If you were to rotate it at 100 MHz, could you build an FM radio transmitter? Supposing it were...
If you were to levitate a superconductor using a permanent magnet due to the effects of the Messiner Effect, and you were then to lift the permanent magnet with your own hands, would you be lifting the mass of the permanent magnet, the mass of the permanent magnet + the mass of the...
Magnet dropped down a copper tube experiment (magnetic braking?)
Homework Statement
Experiment: what is the effect of the # of magnets on the time of drop through the pipe?
Magnets are placed in a paper cylinder container
- "one magnet" is 1 magnet and 5 weights (mass of 1 magnet and 1...
Im looking to do some projects with permanent magnets.
I don't have access to a gaussmeter and I'm wondering if there are any sites that have representations, descriptions or formulas for the field strengths of ferrite or neodymium magnets.
Also i need to learn about how magnetic fields...
Hi,
Recently I came across an annular permanent magnet (round magnet with a hole in it) which had fallen and broken in half, effectively forming two horse-shoe magnets. I noticed that the two halves had similar poles:
|---------- S S--------
| |
|...
Homework Statement
Homework Equations
The Attempt at a Solution
What is the expression for the magnetic field of a magnet? Biot Soviet law cannot be used since there is no current. What should I do? I get stuck at the final step shown below.
I am working with an application where we have a magnet in close proximity to an antenna in the 20 - 25 GHz range. If there IS and affect of the magnet to the antenna's transmission, does the "near field" calculation apply (λ/2xpi)? If the antenna is out of the near field, is there no affect...
Magnetism of a bar magnet -- maximum rate of change?
If a bar magnet is placed along the x-axis with (0,0) at its center, along which axis does the magnetic field fall off faster and why?
Hi
I want to pass DC current through a magnet, essentially using it as connector. The magnet I am using specifically is Neodymium (NdFeB) grade N42. The DC current I would like to pass through it is 100mA ~ 150mA (3V DC ~ 7V DC)
I would like to know if there is any downside to the magnetic...
Hey guys..
I trying to build an magnet which can pull an object with 5N..
I am using S37 as my the iron for my horseshoe magnet,
And been using this formula to convert Newtonian Force to magnetic force
\vec{F}=\frac{B}{µ0}*A
A= cross sectional area = 0,002*1/100 M^2
B = Magnetic Force...
Homework Statement
A sphere magnet of radius a has permanent uniform magnetization, z-axis. So we were trying to find the magnetic field at the center of the magnet in class.
Homework Equations
j_M(θ)=Msin(θ)
dI=j_M(θ)adθ
circular loop
r_{loop}=asin(θ)The Attempt at a Solution
When using...
Is there a way to calculate the magnetic field strength, B, of a magnet (permanent magnet, not an electromagnet) at a certain distance? I assume it follows the inverse square law, but other than that, I do not know what to do.
Tools I have available:
permanent magnet
ammeter/voltmeter...
In physics lab we positively charged a metal sphere then placed a compass near it and both ends of the compass were attracted to the sphere. I know magnetic fields are created by electrons, so I made the assumption the compass is attracted to the positive charge because the electrons in the...
The Idea
The idea is similar to a pendulum in motion. I noticed that it was possible to shift the weight towards a single direction causing an immediate force, which equalized over time. I figured I could use magnets to simulate a pendulum and also reset to the starting state using both...
New here, hello all.
My question is more about the field magnet in a running DC motor. First of all, does the current required to maintain a magnetic field change with the load on the motor? And if so, where would this "extra energy" come from in a permanent magnet DC motor?
I am reading a paper where the bending power of a dipole magnet is described as 2 Tm. Is that Tesla*meter? Is bending power actually power i.e. Work/Time? Can someone explain this physical quantity to me, please?
Homework Statement
Today, my teacher gave us some practice AP multiple choice and my friend and I were debating between answer choices H and J (changed from A and B to remove any confusion) the question as i remember it:
blah blah... B-field into the page, constant velocity v, radius R and...
When a magnet has a value of.. let's say 10 Tesla, what does this mean exactly? Does this mean the magnetic field value directly on the poles has a value of 10 Tesla?
I'm an inventor and I have an idea involving magnets. Unfortunately, I'm having a hard time trying to interpret magnetic equations. Please forgive me if I sound like a noob.. I'm new to magnetism.
Lets say you have a bar magnet with a field B, oriented perpendicular to a wooden interface...
I was wondering what voltage or current, if any, would be produced if the basic magnet through a copper coil experiment had the poles rotated 90 degress so north and south faced the top/bottom of the coil rather than the entry/exit points?
The attached image has a basic illustration of this...
After watching a fascinating youtube video demonstrating the Lenz Effect using a 1.5T MRI machine and an aluminum block, I was wondering if it would stop a bullet fired along the axis of the machine. If so, would there be any defensive military application?
Hello all,
This is just a question i have... I need to know the frequency (in order to meter it) from an electromagnetic source, and i know that a neodymium magnet will disrupts it. so, i want to know what range the neodymium will disrupt, in order to know what device will need to meter...
I've been wondering how does this motor work (if it is not hoax in the first place)
I was thinking about Ampere's force but apparently it doesn't really have an affect here. Any ideas?
I have a device like this one: http://www.youtube.com/watch?v=kA_hw_lY-OY (All of them work the same)
Here's an image:
I want to make it spin without touching it with hands.
I tried using magnets of several kinds, and tried to put them in many places around it but it didn't make it...
how does a magnet create its magnetic field.??
we know, magnetic field is a consequence of velocity attained by a charge..In case of magnet(naturally formed) how do they have magnetic field around them..If it is due to velocity of electrons in it,then all particles should have magnetic field to...
I am studying Mechanical Engineering at college, so please forgive me for any assumptions I make.
I know (been told) that magnets are used to convert mechanical energy into electrical energy. And have no energy of their own. I have been thinking why a magnetic generator powering it self will...
I find it difficult to visualise how the magnetic field generated by a coil can be the same as the field of a permanent magnet. Are the magnetic fields the same or is it just that the effects are the same in that they both attract iron or magnets in the same fashion?
Visualising the field...