Sink or Source [A little OT]
Archiver
Posts: 46,084
If you are discussing this with students who might also be taking physics,
you might point out that Ben Franklin (who gave us the notion of + and -)
had a fifty-fifty chance of getting it right and did not.
Electrical current is a flow of charge typically caused by electrons moving.
Electrons come out of the - side of a battery and reenter through the +
side. Since this is backwards to what makes sense, we pretend it is the
other way.
Of course, there is an opposing view. Have a look at
http://www.amasci.com/miscon/eleca.html which says, in part:
Many authors bemoan the fact that Ben Franklin labled "resinous electricity"
as negative, and "vitreous electricity" as positive. By choosing the
polarities this way, Franklin forces us to say that electric current is a
flow of NEGATIVE charge rather than positive charge.
Did Franklin make a mistake? ABSOLUTELY NOT. In fact it's a blessing,
because flows of negative charge aren't inherently confusing. Common and
widespread misconceptions make them confusing. If Franklin had instead
chosen electrons to be positive, then we could easily ignore those
misconceptions. We'd end up with the illusion of understanding, yet we'd
have all sorts of niggling unanswered questions caused by the
misconceptions. The solution is not to cover up the misconceptions and
pretend that we understand electricity. The solution is to confront our
misconceptions. If we dislike negative currents or find them to be
confusing, it's because our misconceptions are fighting back.
What misconceptions? There are several:
Electric currents are flows of electrons.
"Electricity" is made of electrons, not protons.
Electrons are a kind of energy particle.
"Electricity" is weightless because electrons are weightless.
Positive charge is actually a loss of electrons.
Positive charge cannot flow.
To create "static" charge, we move the electrons.
These seven statements are wrong. We have Ben Franklin to thank for rubbing
our noses in this fact. If he had picked the polarities so that the
electrons came out positive, we might never even notice the problem.
Here are the corrections for the above seven mistakes:
Electric currents are flows of charge. If either the protons or the
electrons flow, that flow is an electric current.
Electrons and protons have very different weights (mass), but both have the
same amount of charge. Electrons are easily removed from atoms, while
protons USUALLY are stuck to other protons, but that doesn't affect the
amount of charge they carry. Electrically, protons and electrons are the
same: they are the two types of charge.
Electrons and protons are matter, not energy. A flow of electrons is NOT a
flow of energy, it is a flow of matter and of charge. Same goes for protons.
"Electricity" (meaning charge) has weight because charge is part of matter
particles, and a flow of charge always requires a flow of matter. Electric
current in a wire is a flow of matter.
Positive charge is not made of "missing electrons." Positive charge is a
genuine type of charge in its own right. Yes, when protons and electrons are
near each other, their charges cancel. Removing the electrons exposes the
charge on the protons, and that's where the misconception originates.
"Static" or imbalanced charges can be created by removing electrons from a
neutral atom. They can also be created by removing charged atoms from an
object, and the removed atoms can be negative OR POSITIVE. It is even
possible to remove bare protons from some materials (after all, protons are
the same as positively charged hydrogen atoms.)
===
99% of the time none of this matters, but it is an interesting point and for
students who will one day take physics you should at least make them
somewhat aware of all this.
Regards,
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller:
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: Paul Verhage [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=xuejf32WwLUv5v3brni-eqUF6IAJHJ6TjlCG499Bh8pP1lUvzoCLS1YE1JpjHTd4I1YV786FPsAwkRBfNFRsyw]pverhage@s...[/url
> Sent: Wednesday, April 18, 2001 8:15 AM
> To: 'basicstamps@yahoogroups.com'
> Subject: RE: [noparse][[/noparse]basicstamps] Re: Sink or Source
>
>
> > Just think of sourcing as "supplying". In the source mode, the I/O
> > pin would supply the current to the device connected - example LED,
> > so that when the I/O pin was set to high, it would go to 5V and
> > supply the connected LED.
> >
> > Sinking can be thought of as "receiving". In sink mode, the I/O pin
> > would receive the current from the connected device and route it to
> > ground, so when the pin was set to low, it would go essentially to 0V
> > and supply a route to ground to activate the device.
>
> This is what I tell my students. It will become a quiz question
> this week.
>
> Paul
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
you might point out that Ben Franklin (who gave us the notion of + and -)
had a fifty-fifty chance of getting it right and did not.
Electrical current is a flow of charge typically caused by electrons moving.
Electrons come out of the - side of a battery and reenter through the +
side. Since this is backwards to what makes sense, we pretend it is the
other way.
Of course, there is an opposing view. Have a look at
http://www.amasci.com/miscon/eleca.html which says, in part:
Many authors bemoan the fact that Ben Franklin labled "resinous electricity"
as negative, and "vitreous electricity" as positive. By choosing the
polarities this way, Franklin forces us to say that electric current is a
flow of NEGATIVE charge rather than positive charge.
Did Franklin make a mistake? ABSOLUTELY NOT. In fact it's a blessing,
because flows of negative charge aren't inherently confusing. Common and
widespread misconceptions make them confusing. If Franklin had instead
chosen electrons to be positive, then we could easily ignore those
misconceptions. We'd end up with the illusion of understanding, yet we'd
have all sorts of niggling unanswered questions caused by the
misconceptions. The solution is not to cover up the misconceptions and
pretend that we understand electricity. The solution is to confront our
misconceptions. If we dislike negative currents or find them to be
confusing, it's because our misconceptions are fighting back.
What misconceptions? There are several:
Electric currents are flows of electrons.
"Electricity" is made of electrons, not protons.
Electrons are a kind of energy particle.
"Electricity" is weightless because electrons are weightless.
Positive charge is actually a loss of electrons.
Positive charge cannot flow.
To create "static" charge, we move the electrons.
These seven statements are wrong. We have Ben Franklin to thank for rubbing
our noses in this fact. If he had picked the polarities so that the
electrons came out positive, we might never even notice the problem.
Here are the corrections for the above seven mistakes:
Electric currents are flows of charge. If either the protons or the
electrons flow, that flow is an electric current.
Electrons and protons have very different weights (mass), but both have the
same amount of charge. Electrons are easily removed from atoms, while
protons USUALLY are stuck to other protons, but that doesn't affect the
amount of charge they carry. Electrically, protons and electrons are the
same: they are the two types of charge.
Electrons and protons are matter, not energy. A flow of electrons is NOT a
flow of energy, it is a flow of matter and of charge. Same goes for protons.
"Electricity" (meaning charge) has weight because charge is part of matter
particles, and a flow of charge always requires a flow of matter. Electric
current in a wire is a flow of matter.
Positive charge is not made of "missing electrons." Positive charge is a
genuine type of charge in its own right. Yes, when protons and electrons are
near each other, their charges cancel. Removing the electrons exposes the
charge on the protons, and that's where the misconception originates.
"Static" or imbalanced charges can be created by removing electrons from a
neutral atom. They can also be created by removing charged atoms from an
object, and the removed atoms can be negative OR POSITIVE. It is even
possible to remove bare protons from some materials (after all, protons are
the same as positively charged hydrogen atoms.)
===
99% of the time none of this matters, but it is an interesting point and for
students who will one day take physics you should at least make them
somewhat aware of all this.
Regards,
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller:
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: Paul Verhage [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=xuejf32WwLUv5v3brni-eqUF6IAJHJ6TjlCG499Bh8pP1lUvzoCLS1YE1JpjHTd4I1YV786FPsAwkRBfNFRsyw]pverhage@s...[/url
> Sent: Wednesday, April 18, 2001 8:15 AM
> To: 'basicstamps@yahoogroups.com'
> Subject: RE: [noparse][[/noparse]basicstamps] Re: Sink or Source
>
>
> > Just think of sourcing as "supplying". In the source mode, the I/O
> > pin would supply the current to the device connected - example LED,
> > so that when the I/O pin was set to high, it would go to 5V and
> > supply the connected LED.
> >
> > Sinking can be thought of as "receiving". In sink mode, the I/O pin
> > would receive the current from the connected device and route it to
> > ground, so when the pin was set to low, it would go essentially to 0V
> > and supply a route to ground to activate the device.
>
> This is what I tell my students. It will become a quiz question
> this week.
>
> Paul
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>