# Spice modelling of back EMF

Started by March 22, 2016
```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.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```On Sat, 26 Mar 2016 11:29:35 -0400, krw <krw@nowhere.com> wrote:

>On Sat, 26 Mar 2016 07:18:21 -0400, Neon John <no@never.com> wrote:
>
>>On Fri, 25 Mar 2016 22:21:37 -0700, John Larkin
>><jjlarkin@highlandtechnology.com> wrote:
>>
>>
>>>The most important first semister freshman Engineering course was
>>>Engineering Design Analysis, taught by the Dean of Engineering. It was
>>>basically dimensional analysis, how to get the units right.
>
>The problem is that some like weird units and some have similar names.

In engineering school, we mostly worked in lbf and slugs and BTUs and
ghastly stuff like that. Luckily, electrical units were already
metric, and I only had to suffer through the mechanics and thermo
courses in olde English. Physics was already in SI.

I still have aerospace customers who work in the old units.
Incredible.

>
>>We covered that the first semester of UPC - Unified Physics and
>>
>Ditto (though just HS physics).

Later times, maybe

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```On Sat, 26 Mar 2016 09:38:48 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Sat, 26 Mar 2016 11:29:35 -0400, krw <krw@nowhere.com> wrote:
>
>>On Sat, 26 Mar 2016 07:18:21 -0400, Neon John <no@never.com> wrote:
>>
>>>On Fri, 25 Mar 2016 22:21:37 -0700, John Larkin
>>><jjlarkin@highlandtechnology.com> wrote:
>>>
>>>
>>>>The most important first semister freshman Engineering course was
>>>>Engineering Design Analysis, taught by the Dean of Engineering. It was
>>>>basically dimensional analysis, how to get the units right.
>>
>>The problem is that some like weird units and some have similar names.
>
>In engineering school, we mostly worked in lbf and slugs and BTUs and
>ghastly stuff like that. Luckily, electrical units were already
>metric, and I only had to suffer through the mechanics and thermo
>courses in olde English. Physics was already in SI.
>
>I still have aerospace customers who work in the old units.
>Incredible.

I was thinking more of the metric units some science disciplines use.
They have their reasons but it makes it a mess for those not intimate
>
>>
>>>We covered that the first semester of UPC - Unified Physics and
>>>
>>Ditto (though just HS physics).
>
>Later times, maybe

Later?  AD, for sure.  ;-) (1968)

As I've said before, we also learned to do arithmetic in bases other
than 10 in fifth and sixth grade ('63ish), though the math curricula
in the secondary schools weren't all that great.
```
```In article <j3e5fb1ipvrth43l7nhsh0cnea2ii7cs7f@4ax.com>,
jjlarkin@highlandtechnology.com says...
>
> On Wed, 23 Mar 2016 09:57:40 -0000 (UTC), Cursitor Doom
> <curd@notformail.com> wrote:
>
> >On Tue, 22 Mar 2016 19:08:14 -0700, John Larkin wrote:
> >
> >> Not to be too pickey, but we don't consider inductors to have "back
> >> emf". That term is usually reserved for motors.
> >
> >So what's your preferred term for the same effect in a solenoid, then?
> >I'm guessing "flyback" perhaps, although this seems to be more of an
> >American English term than anything else.
>
> Flyback, kickback, elldeeeyedeetee maybe. I just don't hear "back emf"
> much around here.
>
> A solenoid is interesting because the armature moves and modulates the
> value of L as it does. Relays, too.
>
> No big deal, as Humpty Dumpty said.

yeah, one way how to detect fule injector movement.

Jamie

```
```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.

Definition: V = N*m/q (Voltage equals Newtons multiplied by meters and
divided by charge in coulombs)

```
```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.
>
>
>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.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```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.
>>
>>
>> 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? I suspect so. And, again, voltage is the unit of EMF
whether you like it or not.

```
```Voltage is electrostatic potential (i.e. potential energy per unit charge), and force is minus the gradient of potential energy. YCLIU.

There were lots of misconceptions about electromagnetic things in the early days, e.g. that you couldn't make a receiver without an earth ground. That's no reason to perpetuate the confusion.

Cheers

Phil Hobbs

(Of course it gets more complicated when you're not in the electrostatic limit, but potential doesn't get any more like a force.)
```
```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.
>>>
>>>
>>> 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.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```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.
>>>>
>>>>
>>>> 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"