>
> Right... So if I let q and Q be the charge of my ball and magnet (what's
the
> correct unit for charge?),

Coulombs (C)

> and I measure r in meters, then F will come out
> in Netwons?

Newtons. Yup.

>While we're on the subject, what would be a suitable range of
> magnitude for q and Q? (The ball is 80g in mass.)

Quite small. The electrostatic forces are very strong

eg. If you give one ball a charge of 5*10^-5 C and the other a charge
or -5*10^-5C and put them a metre apart the force between them is 22.5 N
That's equivalent to the gravitational force exerted by the earth on an
object of
mass 2.2kg.

If you charge a plastic rod by rubbing it with fur you can typically get a
charge
of 10^-9 C

Gail
--
#macro G(H,S)disc{0z.4pigment{onion color_map{[0rgb<sin(H/pi)cos(S/pi)*(H<6)
cos(S/pi)*(H>6)>*18][.4rgb 0]}}translate<H-5S-3,9>}#end G(3,5)G(2,5.5)G(1,5)
G(.6,4)G(.5,3)G(.6,2)G(1,1)G(2,.5)G(3,.7)G(3.2,1.6)G(3.1,2.5)G(2.2,2.5)G(9,5
)G(8,5.5)G(7,5)G(7,4)G(7.7,3.3)G(8.3,2.7)G(9,2)G(9,1)G(8,.5)G(7,1)///GS

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> Right... So if I let q and Q be the charge of my ball and magnet (what's
the
> correct unit for charge?), and I measure r in meters, then F will come out
> in Netwons? While we're on the subject, what would be a suitable range of
> magnitude for q and Q? (The ball is 80g in mass.)
>

btw, I wouldn't mix magnets and electrostatic charges. The math can get very
complex.
Stick to two charges balls and it's not that hard.

Gail
--
#macro G(H,S)disc{0z.4pigment{onion color_map{[0rgb<sin(H/pi)cos(S/pi)*(H<6)
cos(S/pi)*(H>6)>*18][.4rgb 0]}}translate<H-5S-3,9>}#end G(3,5)G(2,5.5)G(1,5)
G(.6,4)G(.5,3)G(.6,2)G(1,1)G(2,.5)G(3,.7)G(3.2,1.6)G(3.1,2.5)G(2.2,2.5)G(9,5
)G(8,5.5)G(7,5)G(7,4)G(7.7,3.3)G(8.3,2.7)G(9,2)G(9,1)G(8,.5)G(7,1)///GS

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> Coulombs (C)

OK, so tell me people - *is* there a "u" in that or not? ;-) Some seem to
think there is, others not...

> >While we're on the subject, what would be a suitable range of
> > magnitude for q and Q? (The ball is 80g in mass.)
>
> Quite small. The electrostatic forces are very strong

So I recall... "A person jumps off the top of a building. It takes him 30
seconds to accelerate down to the bottom under gravity, but only a fraction
of a second for electrostatic forces to bring his bode to a half again.
[Presumably rearranging it beyond recognition in the process!]"

> eg. If you give one ball a charge of 5*10^-5 C and the other a charge
> or -5*10^-5C and put them a metre apart the force between them is 22.5 N
> That's equivalent to the gravitational force exerted by the earth on an
> object of mass 2.2kg.

Ah... yes, *charge balls*... I had _better_ remember to give them OPPOSITE
charges... presumably they'll repell instead of attract otherwise? (Hmm...
that might actually be useful later on...)

> If you charge a plastic rod by rubbing it with fur you can typically get a
> charge
> of 10^-9 C

So I take it a 1C is a fairly large charge then? (I remember hearing that 1
Farrid is larger than any capacitor ever built - "built" being the word!)

> Gail

Thankyou very much!

So, in summary, I have three "magnets" (at least, fixed points which I want
to "attract" a moving particle). Right... so I need r in meters, q and Q
with opposite sign and at around about 10^-7 C or so, and the formula will
give me an answer in Newtons which should be halfway sane (assuming I make
sure that r stays away from zero!) Right, will try...

Thanks again for all the people who bothered to help a hapless half-brain!
Andrew.

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> btw, I wouldn't mix magnets and electrostatic charges. The math can get
very
> complex.

Mmm... complex is bad... (Unless it involved the square root of -1 ;-)

> Stick to two charges balls and it's not that hard.

Sounds good to me...

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Andrew Coppin wrote:

> So I take it a 1C is a fairly large charge then? (I remember hearing that 1
> Farrid is larger than any capacitor ever built - "built" being the word!)

http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=8556534&St=3685&St2=71679322&St3=65133449&DS_ID=3&Product_ID=118270&DID=7

-- 
Ken Tyler

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> Andrew Coppin wrote:
>
> > So I take it a 1C is a fairly large charge then? (I remember hearing
that 1
> > Farrid is larger than any capacitor ever built - "built" being the
word!)


I used to work at the fusion research center here in the UK, and my office
was litterally meters from a room where they had 1000's huge caps - each
about 25cm in diameter. anyway they would charge them up and discharge them
through the plasma to induce currents of 1+ mega-Amps (hence the name MAST -
mega Amp spherical tokomak)

jim

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Waheeeeeeeeey! [Dancing round the room like an insane thing possed] It
works! It works! Yipeeeey!

[Calms down for a moment]

The charge ball formula [eventually] worked a treat! I now have everything
[almost] as I want it - except a post in povray.animations as soon as I
finish uploading the results to my website...

Andrew.

["From the ashes of disaster grow the roses of sucess!..." [etc]]

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Lutz-Peter Hooge <lpv### [at] gmxde> wrote:
> But then it is no orbit at all. Of course it can collide, or escape to 
> infty, but if it orbits at all, it will orbit forever (that is what I 
> mean with stable).

  Of course it's an orbit. It's an unstable orbit.

  Besides, making a difference between them does not help finding a stable
orbit.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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"Andrew Coppin" <orp### [at] btinternetcom> wrote in message
news:3d9755af@news.povray.org...
> > Coulombs (C)
>
> OK, so tell me people - *is* there a "u" in that or not? ;-) Some seem to
> think there is, others not...

My physics textbook says yes.

> Ah... yes, *charge balls*... I had _better_ remember to give them OPPOSITE
> charges... presumably they'll repell instead of attract otherwise?

That's correct.

> (Hmm...
> that might actually be useful later on...)
>
> > If you charge a plastic rod by rubbing it with fur you can typically get
a
> > charge
> > of 10^-9 C
>
> So I take it a 1C is a fairly large charge then?

Yes, very. Two charges, one 1C and the other -1C seperated by a metre
will attract with a force of  about 9*10^9 N (equivalent to the weight of a
900000000 kg object on earth........)

>(I remember hearing that 1
> Farrid is larger than any capacitor ever built - "built" being the word!)

I've heard of a 1 Farad capacitor, never seen one though.

> Thankyou very much!
>
> So, in summary, I have three "magnets" (at least, fixed points which I
want
> to "attract" a moving particle). Right... so I need r in meters, q and Q
> with opposite sign and at around about 10^-7 C or so, and the formula will
> give me an answer in Newtons which should be halfway sane (assuming I make
> sure that r stays away from zero!) Right, will try...

If you need more help with equations please ask.

Gail
--
#macro G(H,S)disc{0z.4pigment{onion color_map{[0rgb<sin(H/pi)cos(S/pi)*(H<6)
cos(S/pi)*(H>6)>*18][.4rgb 0]}}translate<H-5S-3,9>}#end G(3,5)G(2,5.5)G(1,5)
G(.6,4)G(.5,3)G(.6,2)G(1,1)G(2,.5)G(3,.7)G(3.2,1.6)G(3.1,2.5)G(2.2,2.5)G(9,5
)G(8,5.5)G(7,5)G(7,4)G(7.7,3.3)G(8.3,2.7)G(9,2)G(9,1)G(8,.5)G(7,1)///GS

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"Gail Shaw" <gai### [at] mwebcoza> wrote in message
news:3d98b505@news.povray.org...

> I've heard of a 1 Farad capacitor, never seen one though.

http://www.maplin.co.uk/
Enter code JR01B (thats a zero) in the search box.
Size: 8.0mm x 21.5mm dia.

Alf

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