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  4. How fast does a magnet attract ?..and other magnet questions !
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How fast does a magnet attract ?..and other magnet questions !

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Offline neilep (OP)

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How fast does a magnet attract ?..and other magnet questions !
« on: 04/03/2007 22:57:20 »
Dear Magnet Experts !


I'm not too sure how to word this...but....say you have a magnet ...is it always putting out pulling stuff ?...even when it has nothing near to attract ?...or does magnet joy only come into effect when a magnetizable thing comes within the magnets grasp !! ?

...also....how fast is the invisible stuff between the magnet and magnetizeable thing moving ?...do you know what I mean ? surely something is being pulled towards the magnet from the magnetizable thing...haw fast does it move ?

I am sure you appreciate the eloquence utilized in my  prevailing upon you my respectful request upon thee to demonstrate your generosity of spirit to  furnish me with an understanding of said magnetic joy.

Thank You

Magnet Enquirer
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Offline lightarrow

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How fast does a magnet attract ?..and other magnet questions !
« Reply #1 on: 06/03/2007 19:08:04 »
Quote from: neilep on 04/03/2007 22:57:20
Dear Magnet Experts !
I'm not too sure how to word this...but....say you have a magnet ...is it always putting out pulling stuff ?...even when it has nothing near to attract ?...or does magnet joy only come into effect when a magnetizable thing comes within the magnets grasp !! ?
...also....how fast is the invisible stuff between the magnet and magnetizeable thing moving ?...do you know what I mean ? surely something is being pulled towards the magnet from the magnetizable thing...haw fast does it move ?
Do you mean which is the magnetic force's speed? It's c (light's speed).
« Last Edit: 06/03/2007 19:15:06 by lightarrow »
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Offline neilep (OP)

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How fast does a magnet attract ?..and other magnet questions !
« Reply #2 on: 06/03/2007 23:21:42 »
Quote from: lightarrow on 06/03/2007 19:08:04
Quote from: neilep on 04/03/2007 22:57:20
Dear Magnet Experts !
I'm not too sure how to word this...but....say you have a magnet ...is it always putting out pulling stuff ?...even when it has nothing near to attract ?...or does magnet joy only come into effect when a magnetizable thing comes within the magnets grasp !! ?
...also....how fast is the invisible stuff between the magnet and magnetizeable thing moving ?...do you know what I mean ? surely something is being pulled towards the magnet from the magnetizable thing...haw fast does it move ?
Do you mean which is the magnetic force's speed? It's c (light's speed).

YES YES YES !!!..THANK YOU THANK YOU !!

I was really upset that this was not answered...is it c ?...wooo..that's fast !!

Thanks again Alberto !
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Offline lightarrow

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How fast does a magnet attract ?..and other magnet questions !
« Reply #3 on: 07/03/2007 19:23:24 »
However, magnetic force is a complicated subject. When your magnet approaches a piece of iron, the magnetic field (which propagates at light's speed) begin to act on the iron atoms making them rotate a little, as a compass needle moves with the earth's magnetic field.
This process, called magnetization, is not as fast, you have to wait some more fractions of seconds to have your complete magnetic force.

Anyway, if you (ideally) had an electromagnet able to produce a perfectly collimated magnetic field, you could attract iron pieces on the moon in 1.28 seconds after switching on your device.
« Last Edit: 07/03/2007 19:25:32 by lightarrow »
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Offline Bored chemist

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How fast does a magnet attract ?..and other magnet questions !
« Reply #4 on: 07/03/2007 20:22:23 »
That electromagnet would have an inductance so you could only change the current through it at a finite rate; how do you define the time from "switched off" to "switched on"?
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Offline lightarrow

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How fast does a magnet attract ?..and other magnet questions !
« Reply #5 on: 08/03/2007 13:24:49 »
Quote from: Bored chemist on 07/03/2007 20:22:23
That electromagnet would have an inductance so you could only change the current through it at a finite rate; how do you define the time from "switched off" to "switched on"?
The magnetic field starts propagating exactly the instant you switch on the power for the first time. After you have switched off the power, the current keep circulating for some times, as you say. You wait until the current stops completely and then you switch on the device again.
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Offline science_guy

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How fast does a magnet attract ?..and other magnet questions !
« Reply #6 on: 08/03/2007 15:48:56 »
I would guess that the magnetic force is independant of the prescence of things to attract.  As shown in some experiments, the field always takes a certian shape of attraction, which would not be the case if it was dependant on anything.

another thing about magnitism that amazes me is that you could have a magnet the size of a quarter, put it an inch above the ground, and you could pick up a paper clip.  compare the sizes of the quarter vs the Earth, and you will see that A magnetic field is exponentially stronger than a gravity field.
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Offline jacob35430

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #7 on: 30/12/2022 20:34:30 »
grear information
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Online Petrochemicals

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #8 on: 30/12/2022 22:50:29 »
Quote from: jacob35430 on 30/12/2022 20:34:30
grear information
Yes, grear indeed.
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Offline vhfpmr

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #9 on: 31/12/2022 12:32:17 »
Quote from: lightarrow on 08/03/2007 13:24:49
The magnetic field starts propagating exactly the instant you switch on the power for the first time.
The magnetic field is proportional to the current, and the rate of current growth is limited by the inductance:
di/dt = V/L in the absence of any resistance,
or in a real solenoid with resistance:
i = V/R(1-e-tR/L)
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Offline Darlalarsen

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #10 on: 03/01/2023 12:34:54 »
Quote from: vhfpmr on 31/12/2022 12:32:17
Quote from: lightarrow on 08/03/2007 13:24:49
The magnetic field starts propagating exactly the instant you switch on the power for the first time.
The magnetic field is proportional to the current, and the rate of current growth is limited by the inductance:
di/dt = V/L in the absence of any resistance,
or in a real solenoid with resistance:
i = V/R(1-e-tR/L)

Isn't there a computer that would do this independently? Or am I missing something.
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Offline Zer0

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #11 on: 16/01/2023 19:11:14 »
Quote from: jacob35430 on 30/12/2022 20:34:30
grear information

I'm Curious!
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Why do New Users join the Forum, then dig into a Specific past OP, & then Comment on it, and finally Disappear never to return?
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Offline paul cotter

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Re: How fast does a magnet attract ?..and other magnet questions !
« Reply #12 on: 17/01/2023 10:46:58 »
Yes indeed, Zero, I have noticed this phenomenon too but I have no explanation. I too have a question, more troubling imho: how can a thread go on and on when clear precise answers have been graciously provided but seemingly to no avail? Without any finger pointing these threads concern the behaviour of electromagnetic waves.
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