# Spice modelling of back EMF

Started by March 22, 2016
```>> My original point was that the term "EMF" is rarely used in electronic
>> design, is an anachronism, and is literally incorrect. Then people
>> started arguing that voltage IS force.
>
>> See the wiki bits on EMF. And volts. And force.

>I did. That's where I got "Definition: V = N*m/q"
>Maybe *you* should read it.

Pofential has all the wrong symmetries for being a force.

For instance:

1. Potential is a relative measure. It's defined as the integral of E dot ds over some arbitrary path joining two points. In the absence of time-varying B fields, it's independent of the path chosen. Thus you can add a constant to the potential everywhere without changing the fields, i.e. without affecting the operation of circuits.

A circuit inside a continuous metal shield won't even notice if you put it on top of a van de Graaf generator at 400 kV.

If voltage were a force, things would get interesting in there. ;)

2. Voltage is a scalar, whereas force is a vector. That is, force has a direction, and voltage doesn't. If I increase the voltage on the above shield can, which direction would that push the electrons inside?

Cheers

Phil Hobbs
```
```On Sun, 27 Mar 2016 06:44:49 -0500, John S <Sophi.2@invalid.org>
wrote:

>On 3/26/2016 2:36 PM, John Larkin wrote:
>> On Sat, 26 Mar 2016 13:57:30 -0500, John S <Sophi.2@invalid.org>
>> wrote:
>>
>>> On 3/26/2016 1:48 PM, John Larkin wrote:
>>>> On Sat, 26 Mar 2016 13:36:33 -0500, John S <Sophi.2@invalid.org>
>>>> wrote:
>>>>
>>>>> On 3/26/2016 11:30 AM, John Larkin wrote:
>>>>>> On Sat, 26 Mar 2016 11:28:22 -0000 (UTC), Julian Barnes
>>>>>> <jb9889@notformail.com> wrote:
>>>>>>
>>>>>>> On Sat, 26 Mar 2016 07:13:46 -0400, Neon John wrote:
>>>>>>>
>>>>>>>> On Fri, 25 Mar 2016 18:02:06 -0700, John Larkin
>>>>>>>> <jjlarkin@highlandtechnology.com> wrote:
>>>>>>>>
>>>>>>>>> On Fri, 25 Mar 2016 12:00:53 -0500, John S <Sophi.2@invalid.org>
>>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>>> This whole thing is prompted by your statement that "Voltage isn't a
>>>>>>>>>> force." You are wrong and you should have your wrists slapped with a
>>>>>>>>>> ruler.
>>>>>>>>>
>>>>>>>>> Volts are measured in volts. Force is measured in newtons.
>>>>>>>>
>>>>>>>> I prefer foot-pounds but I won't quibble the point.
>>>>>>>>
>>>>>>>> The two are directly related.  Let's see if you can show us the math.
>>>>>>>>
>>>>>>>>
>>>>>>>> spoiler:
>>>>>>>> http://www.electrical4u.com/electrostatic-type-instruments-construction-
>>>>>>> principle-torque-equation/
>>>>>>>>
>>>>>>>> John
>>>>>>>
>>>>>>>
>>>>>>> John Larkin, you stand accused of talking nonsense. How do you plead?
>>>>>>
>>>>>> Guilty of getting an A in my dimensional analysis course.
>>>>>>
>>>>>> Voltage can, in the right experimental setup, result in force. But
>>>>>> voltage is not force.
>>>>>>
>>>>>> If it is, other setups could prove that voltage=current and
>>>>>> voltage=frequency and voltage=pizzas. So we don't need any units at
>>>>>> all.
>>>>>
>>>>> Please check your first year physics textbook.
>>>>>
>>>>> Definition: V = N*m/q (Voltage equals Newtons multiplied by meters and
>>>>> divided by charge in coulombs)
>>>>
>>>> Exactly. Volts are not Newtons. Voltage is not force.
>>>>
>>>> You could use your exact same logic to claim that voltage is distance.
>>>> We wouldn't use a voltmeter, we'd use a meter meter, or a yardstick in
>>>> the USA.
>>>
>>> Ah! I now see the origin of of your point. You are fine-tuning your
>>> responses to continue an ongoing posting to stroke your ego.
>>>
>>> I should have said that voltage produces a force. Would you have argued
>>> against that?
>>
>> Voltage can produce force in some situations. The dimensional reality
>> that volts <> newtons requires that other hardware and other units are
>> necessary for volts to make force.
>>
>> Dimensional analysis is very powerful. Confusing units is sloppy and
>> dangerous.
>>
>> My original point was that the term "EMF" is rarely used in electronic
>> design, is an anachronism, and is literally incorrect. Then people
>> started arguing that voltage IS force.
>>
>> See the wiki bits on EMF. And volts. And force.
>
>I did. That's where I got "Definition: V = N*m/q"
>
>Maybe *you* should read it.

V = I*R, therefore voltage equals current.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```On Sun, 27 Mar 2016 08:25:45 -0700, John Larkin wrote:

> V = I*R, therefore voltage equals current.

You're getting worse, if that's possible.

```
```On Sun, 27 Mar 2016 16:23:52 -0000 (UTC), Julian Barnes
<jb9889@notformail.com> wrote:

>On Sun, 27 Mar 2016 08:25:45 -0700, John Larkin wrote:
>
>> V = I*R, therefore voltage equals current.
>
>You're getting worse, if that's possible.

Do you think that voltage is force?

Dimensional analysis can be used in the forward direction to suggest
design. If you do want to have a voltage create a force, you can look
at all the correct dimensional units and decide what hardware you'll
need.

Force = f(volts, xxx, yyy...) tells you that you need some xxxs and
yyys to do the job. If you get the units right.

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

```
```On Mon, 28 Mar 2016 11:25:01 -0700, John Larkin wrote:

> On Sun, 27 Mar 2016 16:23:52 -0000 (UTC), Julian Barnes
> <jb9889@notformail.com> wrote:
>
>>On Sun, 27 Mar 2016 08:25:45 -0700, John Larkin wrote:
>>
>>> V = I*R, therefore voltage equals current.
>>
>>You're getting worse, if that's possible.
>
> Do you think that voltage is force?

It's really more of a *pressure* but I imagine you'll pick an argument
with that, too.

```
```On Mon, 28 Mar 2016 21:53:44 -0000 (UTC), Julian Barnes
<jb9889@notformail.com> wrote:

>On Mon, 28 Mar 2016 11:25:01 -0700, John Larkin wrote:
>
>> On Sun, 27 Mar 2016 16:23:52 -0000 (UTC), Julian Barnes
>> <jb9889@notformail.com> wrote:
>>
>>>On Sun, 27 Mar 2016 08:25:45 -0700, John Larkin wrote:
>>>
>>>> V = I*R, therefore voltage equals current.
>>>
>>>You're getting worse, if that's possible.
>>
>> Do you think that voltage is force?
>
>It's really more of a *pressure* but I imagine you'll pick an argument
>with that, too.

So it's not measured in Newtons, it's measured in Pascals?

We use "volts", which seem to work.

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

```
```Phil Hobbs wrote:
>>> My original point was that the term "EMF" is rarely used in electronic
>>> design, is an anachronism, and is literally incorrect. Then people
>>> started arguing that voltage IS force.
>>
>>> See the wiki bits on EMF. And volts. And force.
>
>> I did. That's where I got "Definition: V = N*m/q"
>> Maybe *you* should read it.
>
> Pofential has all the wrong symmetries for being a force.
>
> For instance:
>
> 1. Potential is a relative measure. It's defined as the integral of E dot ds over some arbitrary path joining two points. In the absence of time-varying B fields, it's independent of the path chosen. Thus you can add a constant to the potential everywhere without changing the fields, i.e. without affecting the operation of circuits.
>
> A circuit inside a continuous metal shield won't even notice if you put it on top of a van de Graaf generator at 400 kV.
>
> If voltage were a force, things would get interesting in there. ;)
>
> 2. Voltage is a scalar, whereas force is a vector. That is, force has a direction, and voltage doesn't. If I increase the voltage on the above shield can, which direction would that push the electrons inside?
>
> Cheers
>
> Phil Hobbs
Your statements may be correct, but how can you Hex-Plain the
Aharonov-Bohm Effect?  Quantum witchery?

```
```John Larkin wrote:
> On Sun, 27 Mar 2016 06:44:49 -0500, John S<Sophi.2@invalid.org>
> wrote:
>
>> On 3/26/2016 2:36 PM, John Larkin wrote:
>>> On Sat, 26 Mar 2016 13:57:30 -0500, John S<Sophi.2@invalid.org>
>>> wrote:
>>>
>>>> On 3/26/2016 1:48 PM, John Larkin wrote:
>>>>> On Sat, 26 Mar 2016 13:36:33 -0500, John S<Sophi.2@invalid.org>
>>>>> wrote:
>>>>>
>>>>>> On 3/26/2016 11:30 AM, John Larkin wrote:
>>>>>>> On Sat, 26 Mar 2016 11:28:22 -0000 (UTC), Julian Barnes
>>>>>>> <jb9889@notformail.com>  wrote:
>>>>>>>
>>>>>>>> On Sat, 26 Mar 2016 07:13:46 -0400, Neon John wrote:
>>>>>>>>
>>>>>>>>> On Fri, 25 Mar 2016 18:02:06 -0700, John Larkin
>>>>>>>>> <jjlarkin@highlandtechnology.com>  wrote:
>>>>>>>>>
>>>>>>>>>> On Fri, 25 Mar 2016 12:00:53 -0500, John S<Sophi.2@invalid.org>
>>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>>> This whole thing is prompted by your statement that "Voltage isn't a
>>>>>>>>>>> force." You are wrong and you should have your wrists slapped with a
>>>>>>>>>>> ruler.
>>>>>>>>>>
>>>>>>>>>> Volts are measured in volts. Force is measured in newtons.
>>>>>>>>>
>>>>>>>>> I prefer foot-pounds but I won't quibble the point.
>>>>>>>>>
>>>>>>>>> The two are directly related.  Let's see if you can show us the math.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> spoiler:
>>>>>>>>> http://www.electrical4u.com/electrostatic-type-instruments-construction-
>>>>>>>> principle-torque-equation/
>>>>>>>>>
>>>>>>>>> John
>>>>>>>>
>>>>>>>>
>>>>>>>> John Larkin, you stand accused of talking nonsense. How do you plead?
>>>>>>>
>>>>>>> Guilty of getting an A in my dimensional analysis course.
>>>>>>>
>>>>>>> Voltage can, in the right experimental setup, result in force. But
>>>>>>> voltage is not force.
>>>>>>>
>>>>>>> If it is, other setups could prove that voltage=current and
>>>>>>> voltage=frequency and voltage=pizzas. So we don't need any units at
>>>>>>> all.
>>>>>>
>>>>>> Please check your first year physics textbook.
>>>>>>
>>>>>> Definition: V = N*m/q (Voltage equals Newtons multiplied by meters and
>>>>>> divided by charge in coulombs)
>>>>>
>>>>> Exactly. Volts are not Newtons. Voltage is not force.
>>>>>
>>>>> You could use your exact same logic to claim that voltage is distance.
>>>>> We wouldn't use a voltmeter, we'd use a meter meter, or a yardstick in
>>>>> the USA.
>>>>
>>>> Ah! I now see the origin of of your point. You are fine-tuning your
>>>> responses to continue an ongoing posting to stroke your ego.
>>>>
>>>> I should have said that voltage produces a force. Would you have argued
>>>> against that?
>>>
>>> Voltage can produce force in some situations. The dimensional reality
>>> that volts<>  newtons requires that other hardware and other units are
>>> necessary for volts to make force.
>>>
>>> Dimensional analysis is very powerful. Confusing units is sloppy and
>>> dangerous.
>>>
>>> My original point was that the term "EMF" is rarely used in electronic
>>> design, is an anachronism, and is literally incorrect. Then people
>>> started arguing that voltage IS force.
>>>
>>> See the wiki bits on EMF. And volts. And force.
>>
>> I did. That's where I got "Definition: V = N*m/q"
>>
>> Maybe *you* should read it.
>
> V = I*R, therefore voltage equals current.
>
>
But some are more equal than others...
```
```> &#2013266080;Your statements may be correct, but how can you Hex-Plain the
>Aharonov-Bohm Effect? &#2013266080;Quantum witchery?

Essentially unrelated. The A-B effect is a phase shift of the wave function of an electron, caused by the magnetic 'vector potential' A. It requires an electron interferometer to measure. It doesn't change the electric potential.

Vector potentials have more complicated symmetry properties than scalar ones, but they're covered in undergraduate E&M, so it's nothing too spooky at all.

Cheers

Phil Hobbs
```