Can you explain voltage sources in series and parallel completely?

[meBigGuy]

I am having trouble understanding the trouble.

Voltage sources in series add. (assuming they are connected + to -) They each supply their potential difference to the flowing current. Like having two water pumps each adding pressure to a constant stream of water being forced through an orfice.

Ideal Voltage sources of different voltages in parallel cannot exist unless there is resistance between them. Otherwise you have a divide by 0 problem (or, an infinite current). if the voltages are the same, then you essentially still have 1 source.

In the real world, when you connect two 1.5V AA cells in parallel, they "equalize" due to internal resistances and chemistry to be effectively a single battery with twice the capacity.

Once you start talking about batteries, resistances, energy capacity, etc, then you need to draw schematics with all the effects/circuit-elements modeled and calculate the results.

 

[phinds]

node-simple a point of connection of two or more circuit elements. but pictorially i don't know what this means. i would guess that it is the dot on a schematic drawing between two elements such as source battery and resistor in each parallel branch.

A node is a place where all points are short-circuited to each other.

Although it IS a dot on most schematics, in fact the node is any point on all of the wires attached to the dot up to but not including the component to which the wire attaches.

 

[graycloud79]

ok let me rephrase this question. similar to asking "why is the moon colored white? or " why is the sky blue", why does voltage in series add up voltages of batteries from + to - as in the photo i uploaded? it's that simple. yet people give me the obvious answer of "that's how their voltages add up" or something like "because the electric fields push the electrons that way". People's responses are similar to "it is because it is"
I am wondering about a theory behind this.
the path of the circuit, with a voltmeter attached is counterclockwise rather than clockwise?
i am looking at pg63 of electricity demystified.
battery E1 has - and + sides. why does the current travel from the + terminal to the next adjacent battery with 9V's - terminal?

 

[graycloud79]

phinds, i understand what you mean about nodes

 

[phinds]

ok let me rephrase this question. similar to asking "why is the moon colored white? or " why is the sky blue", why does voltage in series add up voltages of batteries from + to - as in the photo i uploaded? it's that simple. yet people give me the obvious answer of "that's how their voltages add up" or something like "because the electric fields push the electrons that way". People's responses are similar to "it is because it is"
I am wondering about a theory behind this.
the path of the circuit, with a voltmeter attached is counterclockwise rather than clockwise?
i am looking at pg63 of electricity demystified.
battery E1 has - and + sides. why does the current travel from the + terminal to the next adjacent battery with 9V's - terminal?

The fundamental construct in a battery is a metal plate. More plates more voltage. Bigger plates, more power available from the plates but no increase in voltage. Stacking batteries is just like adding more plates to a single battery, so more batteries in series == more plates in series == more voltage. Putting batteries in parallel is like making the plates bigger on a single battery ... the voltage doesn't go up but the power available does go up.

 

[graycloud79]

here is a new response i got from a different source:
https://answers.yahoo.com/question/index?qid=20140622143033AAdyCih

 

[graycloud79]

thanks phinds. i sort of understand now. it's like -+-+-+, - and + being plates

 

[graycloud79]

this is what a battery looks like inside. i didn't see any plates

 

[phinds]

this is what a battery looks like inside. i didn't see any plates

Sure you did, they just weren't flat the way they are in car batteries. The anode (the + plate) is a spike in the middle and the cathode (the - plate) is the bottom circle. They identify them in the video but since they're not flat they don't refer to them as plates. In the first batteries made, it was always plates and it still is in car batteries (well, I THINK it is).

 

[meBigGuy]

A single cell battery has a + "plate" and a - "plate" (an anode and a cathode). That one "plate" is shaped like a rod in a D cell makes no difference. Read a little about batteries and how they work.

Potentials in series add. If one person is pushing, he can do a certain amount of work. If two people are pushing they can do more (move more or move faster against a given load). Voltage is kind of analagous to the pressure they produce.

Electron moves into a field and picks up energy, moves into another field and picks up more. Weight is moved up a ladder, gains potential energy. Move it up some more and it gains more potential energy.

 

[graycloud79]

found another helpful link:
http://www.ibiblio.org/kuphaldt/electricCircuits/DC/DC_5.html

it shows arrow signs for more detail on where the current is going at any given time.

 

[graycloud79]

found a helpful link:
https://www.boundless.com/physics/circuits-and-direct-currents/resistors-in-series-and-parallel/charging-a-battery-emfs-in-series-and-parallel/

 

[graycloud79]

another helpful link:
http://people.sinclair.edu/nickreeder/eet150/mod03.htm

 

[graycloud79]

i found a clear easy to understand link:
http://plaza.obu.edu/corneliusk/ec/

they explain better than you guys did because they have diagrams that are more clear to understand

 

[graycloud79]

What are the currents in the branches and the current leading back to battery?
what are the currents of i1, i2, and i3?
correct me if i am wrong?

see this link for the photo:
https://answers.yahoo.com/question/index?qid=20140624141132AAGWlYr

 

[graycloud79]

can you answer this question: https://answers.yahoo.com/question/index?qid=20140624162255AAi0PkA

 

[davenn]

can you answer this question: https://answers.yahoo.com/question/index?qid=20140624162255AAi0PkA

they are the same, the switch shorts out the globe in both circuits, its irrelevant if one is drawn above the other

Dave

 

[graycloud79]

ok let me ask another question in the same schematic drawings as similar post, let's pretend instead of light bulb, and a switch, it's a resistor in its place, doesn't the position relative to the battery indicate which branch receives current first? (even if it's a nanosecond difference) because it's closer to the + terminal than the other branches?
https://answers.yahoo.com/question/index?qid=20140624181825AAk4bUr

 

[davenn]

Marek's answer would have been what I would have told you

in the scheme of things ... its irrelevant
Start dealing with microprocessors running at very high clock speeds and then it starts to become relevant

and incidentally I could build the 3 resistor circuit you have shown and ALL 3 resistors would be the same distance from the battery !

Something you need to learn and understand...
The way a circuit is drawn as a schematic and the way it is constructed in real life are two VERY DIFFERENT things


Dave

 

[sophiecentaur]

@graycloud79
If I were you, I would start on this subject by following the basic rules and definitions and see where they lead you in a practical situation. A practical situation will always always always involve a finite (internal) resistance in series with any 'voltage source' and, when two such sources are connected in parallel, there is the likelihood of large currents flowing through these series resistances. (Different nominal emfs). Nothing magic or paradoxical here - just real life.
The notion of connecting idea voltage sources in parallel (and also connecting ideal current sources in series) is actually nonsense and hasn't any relevance to EE. Likewise, no one considers massless objects in mechanics problems or infinitely long, rigid rods and expects to get any sense out of the result.