Re: [Phys-L] e/m apparatus

[Dan Beeker <debeeker@comcast.net>]

I so miss the old Sargent Welch apparatus. It was the first “experiment” I did in my first time teaching first year e&m. There was  fascinating amount of physics and when you minded your 'p's and ‘q’s with the right instruments you got 1% or so results. It was the lab that inspired my students to work through the tough spots and keep at it when nothing seemed to work right. Was a fine lab for measurements. Our apparatus had big (1m?) coils to cancel the earth’s magnetic field. iirc they had square conductors that were carefully wrapped to get a tight coil. They may have been rewound but suspect they came that way from SW.  Made a difference which side of the heater was grounded as well as whether one used ac or dc for the heater. The tube was big enough to easily see the beam and make measurements. Correcting for refraction through the glass tube was also a challenge. I suppose working with high voltages carries too much liabiity but they are so rich in phyisics concepts I would love to see the things reappear, even if they are used in the advanced labs. I so wish they would have a reincarnation.

Dan

> Date: Wed, 7 Jun 2017 22:47:47 -0700
> From: bernard cleyet <bernard@cleyet.org>
> To: Phys-L@Phys-L.org
> Subject: Re: [Phys-L] e/m apparatus
> Message-ID: <87853D54-2BEB-4C9C-9BE1-3FAEA6174F59@cleyet.org>
> Content-Type: text/plain;	charset=utf-8
>
>
> > On 2017/Jun/07, at 11:45, Peter Schoch <pschoch@fandm.edu> wrote:
> >
> >
> > Finally I used the 'known' and worked backwards, and the built-in scale
> > seems to be the culprit.  Irksome, to say the least, for that kind of money.
>
>
> IIRC, ?We? (the students) obtained rather gud results from the Welch fifties system (ca. 1986).  (Don?t have reports handy, but do have detailed instructions about error, etc,). 
>
> I thought at the time to x-ray the tube using our GE-XRD.  I?d get a v. large screen/film from a clinic and have the tube and screen v. far from the diffraction port.  
> I didn?t ?get around? to calculating how parallel the ?rays? would be.  V. large lab. tho.  
>
>
> bc, has complete Busch method from UCB   (Coils, 2?BP1, P/Ss), and wonders the % error Peter obtained.  
>
>
> http://aapt.scitation.org/doi/pdf/10.1119/1.1937814
>
>
> Has anyone calculated the field variation for the Helmholz?   
>
> ------------------------------
>
> Message: 4
> Date: Thu, 8 Jun 2017 08:48:20 -0500
> From: brian whatcott <betwys1@sbcglobal.net>
> To: phys-l@mail.phys-l.org
> Subject: Re: [Phys-L] e/m apparatus
> Message-ID: <f737f3f6-b1ff-1fe0-db1c-defe89ea6bf0@sbcglobal.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Interesting question about  Helmholz coils from bc.
> The field variation within the coil-enclosed volume is well-known.
> In situations where uniformity is important, the coil diameter is large 
> compared to the experimental volume of interest.
>
> Brian W
>
>
> On 6/8/2017 12:47 AM, bernard cleyet wrote:
> > /snip/
> > bc, has complete Busch method from UCB   (Coils, 2?BP1, P/Ss), and wonders the % error Peter obtained.
> >
> >
> > http://aapt.scitation.org/doi/pdf/10.1119/1.1937814
> >
> >
> > Has anyone calculated the field variation for the Helmholz?
> > _______________________________________________
> > Forum for Physics Educators
>
>
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