magnet theory

Discussion in 'General Electronics Chat' started by walters, Jan 1, 2006.

Not open for further replies.
1. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
Alnico magnets are used for guitars alots but there is different mixtures
like Alnico I-II-III-IV-V different mixtures of Alnico

Is a magnet the same as a inductor ? i don't get about these different types of mixtures because they all have different frequency responses
why is that and how can u tell about a magnets frequency response?

a Magnet with wire turns around a pole = a coil

Whats the theory on Electro Magnets? im new to this stuff

Because winding the wire about the magnet can produce different frequency responses, Q points, resonances, midrange boost or midrange peaks how?

2. mstechcaNew Member

Joined:
Mar 28, 2003
Messages:
1,595
Likes:
1
Location:
Why do you care?
Yes and No.
At a basic point of view, an inductor is a piece of wire wound many times. I'm not going to explain what a magnet is because you should know what a magnet is.

When an inductor is used in an electronic circuit, it produces a magnetic field.

this describes an inductor with a magnetic core.

3. OznogActive Member

Joined:
Apr 21, 2004
Messages:
2,879
Likes:
11
Location:
Austin, Tx
A magnet is not usually wound to make an inductor. An inductor core is made out of a magnetic iron-based material but it is designed to not be permanently magnetized. It gets temporarily magnetized when current is passed through the coil.

When you have a moveable permanent magnet move inside a coil, the changing magnetic field creates current. That's how motors and the non-condensor type microphones work.

A permanent magnet doesn't really have a frequency response since it only creates a constant field. That being said, I can't rule out subtle nuances in its properties that would affect the frequency response of a speaker.

Joined:
Jan 12, 1997
Messages:
-
Likes:
0

5. mstechcaNew Member

Joined:
Mar 28, 2003
Messages:
1,595
Likes:
1
Location:
Why do you care?

I don't think you can wind up magnets anyways :lol:

There are air core inductors. and you can even make one yourself!

the "coil" is the inductor. is it not?
at least the coil is responsible for providing the inductance value.

6. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
What is a magnet then is it a LCR network?

Because there is different mixtures when making magnets what does this do ?

Magnets have different frequency responses from different mixtures why is that?

How can a magnet have different frequency responses? what kind of component is a magnet a inductor,resistor,cap?

7. mstechcaNew Member

Joined:
Mar 28, 2003
Messages:
1,595
Likes:
1
Location:
Why do you care?
not even close :lol:

an LCR network is an inductor, capacitor and a resistor connected together in some way, shape, or form.

what does what do?

Didn't someone tell you that magnets don't have a frequency response?

like the poster above you said, THEY DONT!

Someone send this guy back to school, he really needs it. I'm sure you can learn 1/2 of this in highschool!

8. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
Thanks for correcting me

How to change the magnetic field?
How to change th flux?
How do change the permeability?

When winding a wire around a magnetic it creates a magnetic field
and then the magnetic and wire from a electromagnetism?

a Coil and a magnet from a current, so changing the flux changes the magnetic field changing the current?

It seems like magic from just taking a magnet and wrapping a wire around it forms a magnetic field and flux and having a current output

It seems like a magnet is a voltage generator?
Its seems like a coil and magnet form a current generator?

9. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
Is the magnetic Field and Flux the same thing whats different about them?

Is The permeability a magnetic field or flux?

What is a permeabiltiy?

10. OznogActive Member

Joined:
Apr 21, 2004
Messages:
2,879
Likes:
11
Location:
Austin, Tx
It'd be hard to explain it, magnetics requires some physics understanding. Lots of web pages can give you an explanation with pics and such.

Understand that permanent magnets are very different things compared to magnetic materials such as used in transformers and inductors. In the transformer, you want to use a coil to change the magnetic flux in the core. A permanent magnet has a fixed, built-in flux that resists change.

A wire in a changing magnetic field produces current. This is not free power though.

One way to do this is moving a permanent magnet past a coil (or vice versa). It's not free because when power is drawn off it there will be "drag" force between them which slows down the moving object.

The other common use is a transformer where there's no motion between the core and the coils. The first coil produces a varying magnetic field so the second coil will experience a changing magnetic field thus produce its own current.

11. mstechcaNew Member

Joined:
Mar 28, 2003
Messages:
1,595
Likes:
1
Location:
Why do you care?
A magnet and a coil cannot produce voltage or current by themselves.

If you want to make voltage, take a motor, and an LED. Connect the LED to the motor. you need to attach the motor to something that spins.
Hey, why not take a bicycle, and attach the end of the motor to it. When you ride your bike, the motor spins, and the LED lights (if the motor is spinning the right way). Go faster, and the LED goes brighter.

I shall compliment you for the fact you love exploring objects, but I think you are asking about stuff that doesn't really matter.

Are you doing a project on magnets for school?

12. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
thanks guys for the help no not school work just need help

so whats the difference betwen a inductor VS a magnet?

a coil is a magnet with wire wrapped around it which is a inductor?

A inductor has Flux and a magnetic field?

A magnet has Flux and a Magnetic field but whats the difference from a inductor they seem like the same thing

13. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
why does the magnetic and wire wrapped around the magnetic cause a resonance frequency?

Joined:
Mar 16, 2004
Messages:
32,588
Likes:
950
Location:
Hi Walters,
I think you are talking about a magnetic pickup for a guitar that has steel strings. When the steel string vibrates near the pickup, an AC voltage is generated in the coil that is wound around the magnet, because the magnetic field from the magnet is disturbed by the string.
The coil has inductance and capacitance in parallel so therefore causes resonance. Additional capacitance can be added in parallel to reduce the frequency of the resonance. The load resistance for the pickup can be reduced to damp resonance or increased to allow resonance.

15. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
Thanks

The coil has inductance and capacitance in parallel

What is the inducatanc and capacitance?

Is the inductance the magnetic?
is the capacitance the magnetic or gauge of wire?

16. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
So the Magnet = is a inductor because of flux,magnetic fields like
a inductor

The Guage of wire- is the capacitance

The wire windings- is the resisantance

Total= LCR= DC resistance= impedance= Resonance Frequency >?
If fender used Alnico 5 then this is a constant FIXED
The only difference is the winding differences and gauge of wire

so L = magnet= constant

C= wire guage

R= Winding differences

17. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
the insulations changes the windings?

The insulation changes the capacitance then?

The insulation changes the winding space?

Does the Bobbin Material change the LCR, flux, magnetic field?
it the Bobbin Material a permability?

18. waltersBanned

Joined:
Jun 4, 2005
Messages:
638
Likes:
0
Where is the ferromagnetism in a guitar pickup?
What does the ferromagnetism in a guitar pickup do?
Does the ferromagnetism change the flux,magnetic field or tone of a guitar pickup?

harmonic oscillator theory affects the resonance frequency? why and how?

A magnet with wire wrapped around it produces a "harmonic oscillator"?
what does this harmonic oscillator do?

19. StyxActive Member

Joined:
Dec 19, 2003
Messages:
1,743
Likes:
9
Location:
UK
the magnet exists in the pickup of an electric guitar. Think of an electric guitar pickup like a linear machine (or not if you are not machine orientated)

As you can see from this picture there are a number of poles (hence the linear machine analogy).

WHen nothing is changing a fixed flux is present in the pickups winding. When a string is plucked (the string MUST be ferrous to effect the field) it changes the magnetic proporties of the system and a changing flux occurs, a changing flux is a XFMR is current and it is this current that is then amplified

THe ferromagnetism as in the magnet present doesnt change the flux, it provides the flux, the strings of the guitar change the relunctance path that the flux can take.

bit confused what you mean here. Harmonic theory is used to calculate the resonant freq, thus they go hand in hand, one doesn't cause the other, it is the same thing just viewed from different angles

ok before I carry on you are going to be entering a world of pain if you really want to get into magnetism. Some of the cleverest ppl I have ever met work in electromag, it is a subject not for the faint harted.

Anyway to just desquell a myth, someone eariler on said that magentsDONT have different freq responses. Well in actual fact they do and it is mainly down to their hysteresis of the B-H curves (rare-earth mags have the worst) , but that is a different story and I dont want to confuse ppl too much.

Now depending what kind of magnet is being used.
Say we had a soft-iron magnet. Wrap a wire around it and put some current through it will cause the soft-iron magnet to become magentised to the field of the coil, the presece of the soft-iron will increase the permeability of the magnetic cct (think of it as a scaling factor)
Air has a perm of 4*PI*10-7
Iron has a perm of many thousand times higher then free air. Thus by adding iron to yr magentic cct you can increase the flux density conciderably (but it comes and limitation naimly saturation)

Now say you put a normaliron core into the coil. A normal iron core keeps it flux (ie a magnet). Now IF oyu put current into the winding one way you will basically canel out the magnet filed of the core and thus the inductance of the coil is zero, the other way you re-inforce the field and teh inductance goes up.

You cannot use MAGNETS in cores for tuned ccts due to this effect (soft iron MUST be used).
Now you increase the flux and you will cross a magic threshlod and you will start to magnetise the core.

Now start using stonger magnets (rare-earth and such) and the same is still true, current one way will cancel the flux (more and field will flop) current the other way and the field will strengthen.

The difference with rare-earth is if the flux get too heigh then their field actually collapsed and it is no longer magentic (well maybe 1% of its original strength)

So that statement abt a magnet with a coil around it being a harmonic oscillator isnt really possible since it will dampen out any oscillation very easily due to the sever mis-symattry of inductance one way to the other.

A soft-iron core will basically be a large inductor, and with in a LRC cct it will resonate at a certain freq

Joined:
Mar 16, 2004
Messages:
32,588
Likes:
950
Location:
The inductance of a coil depends on the number of turns, the core material, its length and its diameter.
The capacitance of a coil depends on how many layers of turns, the spacing of its layers and turns, its length and its diameter.
The resonant frequency can be measured or calculated.

A magnet is not an inductor. A coil of wire is an inductor.

A magnet positioned inside a coil becomes the core of the coil. The ferrous core increases the inductance of the coil. The combination is an AC generator if the magnetic field is disturbed by moving the coil or magnet (dynamic microphone, magnetic phono pickup) or vibrating a steel string near it (guitar pickup).

21. StyxActive Member

Joined:
Dec 19, 2003
Messages:
1,743
Likes:
9
Location:
UK
Ahh yes a moving-coil well that is a special case for a magnet within a coil, but then again that is just an electrical machine...