FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Science and Technology » Physics » Electromagnetics
E-FIELD questioned instead of CIRCUIT THEORY titans V and I
Post new topic   Reply to topic Page 1 of 1 [2 Posts] View previous topic :: View next topic
Author Message
G Patel
science forum beginner


Joined: 02 May 2005
Posts: 49

PostPosted: Mon May 02, 2005 6:37 pm    Post subject: E-FIELD questioned instead of CIRCUIT THEORY titans V and I Reply with quote
I have uploaded a diagram of a simple circuit here
(http://www.geocities.com/likkle_gaya/ElectricFieldSimpleCircuit.JPG).
The diagram has emphasis placed on the valence and conduction band
electrons of the copper wires. I know that there exists a voltage
difference between the wires and can calculate current, etc. but now
I'm trying to understand this circuit in terms of vector quantities
(Electric Fields, Forces, Charge Separation, Drift Velocity).

Is my portrayal of the charge differences (charge density?) between the
two conducting wires accurate? If so, since the current is equal in
them, the drift velocity of the electrons in the High Potential Wire
must be higher to compensate for the different in charge densities. Is
this right?

Please bear with me, because I'm trying to get visual/illustrative
intuition about circuits like this (without resorting to scalar
quantities and vague/simplistic analogies of "voltage pressure"). Can
anyone explain how the VOLTAGE difference is represented in circuits
like this? I know the mathematics of voltage, electric field, electric
force (Coloumb's law), etc. and I know how to do scalar calculations
with these circuits, but the connection between these two entities gets
blurred once I stare at a circuit like this.

Any help will be appreciated. Please no answers that talk about water
hoses, cliffs, "pressure", or "energy drops." I am well aware of these
analogies and ideas(mathematically)- what I am looking for now is a
particle level illustrative answer/explanation.

Thanks to all.
Back to top
operator jay
science forum Guru Wannabe


Joined: 29 Apr 2005
Posts: 142

PostPosted: Wed May 04, 2005 6:11 am    Post subject: Re: E-FIELD questioned instead of CIRCUIT THEORY titans V and I Reply with quote
"G Patel" <gaya.patel@gmail.com> wrote in message
news:1115066264.528802.74260@l41g2000cwc.googlegroups.com...
Quote:
I have uploaded a diagram of a simple circuit here
(http://www.geocities.com/likkle_gaya/ElectricFieldSimpleCircuit.JPG).
The diagram has emphasis placed on the valence and conduction band
electrons of the copper wires. I know that there exists a voltage
difference between the wires and can calculate current, etc. but now
I'm trying to understand this circuit in terms of vector quantities
(Electric Fields, Forces, Charge Separation, Drift Velocity).

Is my portrayal of the charge differences (charge density?) between the
two conducting wires accurate? If so, since the current is equal in
them, the drift velocity of the electrons in the High Potential Wire
must be higher to compensate for the different in charge densities. Is
this right?

Please bear with me, because I'm trying to get visual/illustrative
intuition about circuits like this (without resorting to scalar
quantities and vague/simplistic analogies of "voltage pressure"). Can
anyone explain how the VOLTAGE difference is represented in circuits
like this? I know the mathematics of voltage, electric field, electric
force (Coloumb's law), etc. and I know how to do scalar calculations
with these circuits, but the connection between these two entities gets
blurred once I stare at a circuit like this.

Any help will be appreciated. Please no answers that talk about water
hoses, cliffs, "pressure", or "energy drops." I am well aware of these
analogies and ideas(mathematically)- what I am looking for now is a
particle level illustrative answer/explanation.

Thanks to all.


I've never heard of there being a difference in density of charge carriers.
To me the electrons at the -ve side of the load have greater electrical
potential energy than those at the +ve terminal. Inside the battery
chemical processes occur, providing energy to force electrons together in
excess at the -ve terminal. The energy is stored in the electric field as
the electrons don't like to be crammed together and work is required to
bunch them. The electrons will use the energy stored in the electric field
to move apart if they are able. Given a path (the wire and the load),
electrons flow away from the -ve terminal of the battery toward the positive
terminal, converting electrical potential energy (energy stored in electric
field) into (ultimately) heat.

Voltage is electrical potential energy per unit charge. Volts = Joules per
Coulomb. A 24V battery gives us electrons with an energy of 24J per Coulomb
of electrons.

With a 24Vdc battery, and a load which is, say, a resistor 0.1m in length,
then your electric field is basically 240V/m along the resistor. Each
electron loses 240 Joules of electrical potential energy per Coulomb of its
charge, for every meter of resistor traversed. So, one Coulomb worth of
electrons loses 24J moving through the resistor (which it must as our 24V
battery would represent 24J/C). Let's say the resistor is 48Ohms. We have
0.5A, or 0.5 Coulombs per second flowing. So, we would lose 12J per second
of electrical potential energy. 12J/s is 12 Watts. Electrons moving
through the electric field are losing electrical potential energy at a rate
of 12W. Our circuit theory agrees, 24V * 0.5A = 12W.

I'm not sure if this is what you are after. You say you know the
mathematics of the fields, forces, etc, and are mathematically well aware of
energy ideas. So it seems like none of the above would be news to you.
However maybe this is a link between fields and cct theory. You can do the
above per electron if you wish. Each electron loses
240V/m * 1.67E-19C * 0.1m =
240N/C * 1.67E-19C * 0.1m =
(240*1.67E-19*0.1)[N m] =
(240*1.67E-19*0.1)[J] =
(24*1.67E-19)[J] =
4E-18J
moving through the resistor.

j
Back to top
Google
Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 1 of 1 [2 Posts] View previous topic :: View next topic
The time now is Thu Jan 08, 2009 4:59 pm | All times are GMT
Forum index » Science and Technology » Physics » Electromagnetics
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts Units for electric field strength Gavin Electromagnetics 0 Thu Aug 24, 2006 3:00 pm
No new posts Infinitesimal generator of a vector f... Julien Santini Math 0 Fri Jul 21, 2006 8:01 am
No new posts unified theory gb6724 New Theories 4 Fri Jul 21, 2006 5:25 am
No new posts Signal Nonlocality Loophole in Quantu... Jack Sarfatti Math 0 Thu Jul 20, 2006 1:59 am
No new posts A Combinatorics/Graph Theory Question mathlover Undergraduate 1 Wed Jul 19, 2006 11:30 pm

Mobile Phone | Guitar Lessons | Online Paid Surveys | Loans | Credit Counseling
Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Electronics forum |  Medicine forum |  Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums


Powered by phpBB © 2001, 2005 phpBB Group

[ Time: 0.2230s ][ Queries: 16 (0.1392s) ][ GZIP on - Debug on ]