Can you explain voltage sources in series and parallel completely?

In summary, the book Electricity Demystified explains that for voltage sources in series, the total voltage is the sum of all individual voltages, and for voltage sources in parallel, the output voltage is the same as any single source. This is due to Kirchhoff's voltage law. However, in real world scenarios, ideal voltage sources in parallel are impossible and can result in damage if the voltages are significantly different. This is because the lower voltage source may block reverse current or be damaged by it. Various online forums and links provide further explanations and discussions on parallel voltage sources.
  • #1
graycloud79
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i would like to know the underlying reasoning why it works the way it does and how it works based on the explanation given by the book Electricity Demystified, but i would like a far better explanation. Give me something like an analogy to better explain it physically.
In there it says:
for voltage sources in series:
E = E1 + E2 + E3 + ...+En (all connected "minus to plus"
with polarity reversal: it is
E = E1-E2+E3+...+En (reverse the polarity of battery number 2 with voltage E2)

for voltage sources in parallel:
in a parallel circuit, the poles must all go "plus-to-plus" and "minus to minus"
the output voltage of a properly designed parallel combination of cells or batteries equals the voltage of any single one of them.

(i think this is due to kirchhoffs voltage law). i would like a of this schematic/drawing of this circumstance.
I=I1+I2+I3+...+In

I have to understand this logically to progress through.
 
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  • #3
thank you mrsparkle. i will review it and see if it is good.
in meantime, i found this link with a photo that explains parallel circuits:
http://www.regentsprep.org/Regents/physics/phys03/bparcir/
 
  • #4
i don't think amasci.com has what i need
 
  • #6
To better understand the nature of your request;

What is your understanding of these terms?

joule, coulomb, volt, ampere, ohm , watt, ?

Meantime you might experiment with a two or three cell flashlight.
 
  • #8
Keep in mind that ideal voltage sources in parallel are impossible, it only works with ones in the real world and even then it's a bad idea if the sources are very far off from each other in voltage. Best case is that the lowest voltage one blocks reverse current in which case it is effectively out of the circuit so would be pointless and worst case is it will NOT block reverse current and be damaged.
 
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  • #9
jim hardy said:
What is your understanding of these terms? joule, coulomb, volt, ampere, ohm , watt, ?
Meantime you might experiment with a two or three cell flashlight.

I don't think i can experiment to any helpful use with a two or three cell flashlight.
Joule-unit of energy in SI derived units
coulomb-a unit of charge (electrons)
volt-the electrical potential energy that a battery has that allows it to release current and energy
ampere-Coulombs / second that pass through a point in a circuit
ohm- voltage/current ratio. tells how resistance a resistor has in a circuit
watt-J/s or joules per second

this doesn't help me learn the exact details of what i am asking because i already knew it
 
  • #10
phinds said:
Keep in mind that ideal voltage sources in parallel are impossible, it only works with ones in the real world and even then it's a bad idea if the sources are very far off from each other in voltage.

Best case is that the lowest voltage one blocks reverse current in which case it is effectively out of the circuit so would be pointless and worst case is it will NOT block reverse current and be damaged.
.........................
that sounds a bit esoteric to me.

Let me reword and formulate my own explanation.
it is impossible to have ideal voltage sources in parallel because you can not have each voltage source (battery), giving out the same voltage precisely as voltage of battery are not always precisely equal due to being partly random and not exactly same.

my explanation is that if you have a voltage source in parallel, as in a battery connected in one of the branches of the parallel circuit, if it was the same voltage as the original start battery, it won't change the voltage due to the voltages of the two batteries being the same, nothing changes in the "electrical pressure".

the reasoning for adding a battery in this branch is to increase more current than a single battery can do on its own. "if the voltages differ, some of the cells or batteries will drive current through others and that's no good! (seems ambiguous wording, what is drive current through others?)"

quote "Best case is that the lowest voltage one blocks reverse current in which case it is effectively out of the circuit so would be pointless and worst case is it will NOT block reverse current and be damaged."
i don't know what this means. please try rewording it.
 
  • #11
more related helpful links:
A Question about Voltage Sources in Parallel https://www.physicsforums.com/showthread.php?t=716941
Two different voltage sources in parallel ! https://www.physicsforums.com/showthread.php?t=634530
Parallel voltage sources circuit https://www.physicsforums.com/showthread.php?t=512536
Two Parallel Voltage sources and KVL https://www.physicsforums.com/showthread.php?t=435172
connect two AC sources in parallel unless they have the same voltage https://www.physicsforums.com/showthread.php?t=321292
 
  • #12
graycloud79 said:
"Best case is that the lowest voltage one blocks reverse current in which case it is effectively out of the circuit so would be pointless and worst case is it will NOT block reverse current and be damaged.
i don't know what this means. please try rewording it.

Let's say you have a 12volt battery and a 1.5volt battery and you hook them in parallel. The 12v will want to push current through the 1.5 volt battery the wrong way. If the 1.5volt battery blocks current that tries to flow through it in the wrong direction then the effective circuit is a 12volt battery and the 1.5 volt battery is not really there.

If the 1.5 volt battery does NOT block reverse current, then it will be swamped with reverse current from the 12volt battery and it may well explode or at the very least be irreparably damaged.

Voltage Power supplies, on the other hand, always (as far as I know) are circuits that have diodes and or transistors in the output path and so naturally block the flow of reverse current so won't be damaged if put in parallel, but the lower voltage one effectively won't be there since its output will be reverse biased.
 
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  • #13
it's hard to understand

let me draw a picture of the circuit or could you possibly do that for me? with comments on it labeling every process/action? I'm not good at learning through words only as it is very confusing for me. i could use an animation to learn best as well but i don't know how to use flash animation to do that.
 
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  • #14
phinds, here is a simple diagram i made. hopefully you can edit it to your explanation
 

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  • #16
graycloud79 said:
I don't think i can experiment to any helpful use with a two or three cell flashlight.
well you could put one cell in backwards and observe the light glowing more dimly. That would confirm what your book says about voltages in series.

Joule-unit of energy in SI derived units
good


coulomb-a unit of charge (electrons)
good


volt-the electrical potential energy that a battery has that allows it to release current and energy
RAZZZ A volt is one joule per coulomb. It is a measure of the energy required to move a coulomb from one place to another. "One place to another" is significant in that it infers a difference not an absolute value - in circuits, voltage is always a potential(energy) difference.



ampere-Coulombs / second that pass through a point in a circuit
ohm- voltage/current ratio. tells how resistance a resistor has in a circuit
watt-J/s or joules per second
well done !

I should have added to the list , "node" .


this doesn't help me learn the exact details of what i am asking because i already knew it

it is not clear to me exactly what you are asking.

It is helpful when starting out to imagine one's self infinitesimally small and inside the circuit drifting along with the [STRIKE]electrons[/STRIKE] charge carriers. [in modern texts, 'conventional' current flow is in opposite direction to electron drift - start out your thinking with conventional current and you'll save yourself a lot of headaches]

In a DC series circuit, as you progress through each circuit element you either acquire or lose energy.
That is why the voltage(potential difference) between the ends of your journey is the sum of the individual voltages(potential differences) including their signs.

In a DC parallel circuit you have only one beginning point and one end point, but with multiple routes to get from one to the other. Between those two points exists only one potential difference.
That is why batteries in parallel must be connected with like polarity, else you have a war of the batteries each trying to impose its potential across the other.

Have fun

old jim
 
  • #17
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.
 
  • #18
jim hardy i am trying to learn the step by step explanation of how voltage sources in series/parallel circuit works. and electrical theory underlying it. in other words what precisely and exactly makes it work the way it do? explain in micro detail like an animation pictorially how it works with step by step explaining in full.

for ex, i will toss out an explanation that may or may not be correct: my explanation would be it changes the path of the current. and it goes this particular way (shown in a diagram/animation)
 
  • #19
here is a diagram i drew myself of voltage sources in series.
 

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  • #20
graycloud79 said:
jim hardy i am trying to learn the step by step explanation of how voltage sources in series/parallel circuit works. and electrical theory underlying it. in other words what precisely and exactly makes it work the way it do? explain in micro detail like an animation pictorially how it works with step by step explaining in full.

for ex, i will toss out an explanation that may or may not be correct: my explanation would be it changes the path of the current. and it goes this particular way (shown in a diagram/animation)

The basic answer is that voltage sources are applied electric fields, and they add in series. When put in parallel, the required current is proportionally divided between them. If this is not a good enough answer, then you have some trouble. Going further into the rabbit hole requires going into some depth with Maxwell's equations. Its a simple enough question, but one that can potentially have a pretty complex answer, depending on how deep into electrical theory you want to go. There are layers of abstraction here that can require some serious knowledge to peel away. Most people can accept that voltage sources add in series without needing to understand the field theory or quantum dynamics.
 
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  • #21
refer to diagram in previous post
so why is a negative terminal of the "main source battery/MSB" connecting to a negative terminal of another 6V battery? just explain this.

i would have thought normally negative current from negative terminal would go to a positive terminal of the same battery. what happens to the current after "MSB's negative terminal electrons reach the 6V battery's negative terminal? where does it go next? and where does it travel precisely?
 
  • #22
what is an applied electric field? provide me an easy to understand answer.
 
  • #24
graycloud79 said:
refer to diagram in previous post
so why is a negative terminal of the "main source battery/MSB" connecting to a negative terminal of another 6V battery? just explain this.

i would have thought normally negative current from negative terminal would go to a positive terminal of the same battery. what happens to the current after "MSB's negative terminal electrons reach the 6V battery's negative terminal? where does it go next? and where does it travel precisely?

you have no current because you have an open circuit.
The voltage difference between the + sign on the bottom and the - sign on the bottom is 30 V.
The voltage difference between the - sign on the bottom and the - sign of the 6V battery is 0. Does this help?
 
  • #25
um actually it's not an open circuit, you just may have interpreted it wrong. there is no hole in the circuit. i was supposed to put E in the gap at the source battery. i will have to trace through what you are saying as it seems a bit unclear.
 
  • #26
refer to diagram in previous post
so why is a negative terminal of the "main source battery/MSB" connecting to a negative terminal of another 6V battery? just explain this.

I don't see a msb in that picture.

attachment.php?attachmentid=70794&d=1403490195.png


i am trying to learn the step by step explanation of how voltage sources in series/parallel circuit works...
in other words what precisely and exactly makes it work the way it do?

Imagine yourself accompanying one coulomb on a trip through your circuit.
We'll start at the negative terminal, ie the dot labelled - .
That dot and the wire going to the 6v battery's negative end comprise a node, and potential is same everywhere on a node(by definition).
You traverse the node and enter the battery.
Inside the battery you acquire potential energy from the chemical reactions and exit the positive terminal with six more joules than you entered.
You enter the next battery and similarly acquire nine more joules.
The next two batteries give you three and twelve more joules respectively.
So you arrive at the +dot with thirty joules more than when you started.
You can deposit them in whatever load is connected between the dots.
That's how voltage sources in series work.
If they were generators it'd be the same just the energy comes from electromagnetic force on the coulombs not electrochemical .

You will learn by working problems to form the habit of applying Kirchoff's laws.
You won't learn by flailing among myriad internet pages.
There's no substitute for drill. That's how you learned your multiplication tables.
 
  • #27
the first 6V battery, does it release a current from it's positive terminal as in electrons flowing from it(+terminal) to the second battery's (9V) +terminal. that makes no sense because electrons usually flow (in the normal simple series circuit schematic i understand) from -terminal to the +terminal of the same battery.
 
  • #28
graycloud79 said:
um actually it's not an open circuit, you just may have interpreted it wrong. there is no hole in the circuit. i was supposed to put E in the gap at the source battery. i will have to trace through what you are saying as it seems a bit unclear.

well, in that case, you have a short circuit. You are probably doing yourself a disservice by not putting a resistor in there to at least simulate the wire. With an ideal abstraction, that closed wire would be both 30 V and 0V simultaneously which is obviously impossible and will confuse you.
 
  • #29
graycloud79 said:
the first 6V battery, does it release a current from it's positive terminal as in electrons flowing from it(+terminal) to the second battery's (9V) +terminal. that makes no sense because electrons usually flow (in the normal simple series circuit schematic i understand) from -terminal to the +terminal of the same battery.

no, electrons flow in the direction the electric field pushes them. All the batteries are pushing in the same direction. The +/- signs are indicating direction of the electric field from the battery. This may be your big source of confusion.
 
  • #30
mrsparkle is there a source website* where i can learn this? i only have a general physics I community college background.
i mean electric fields and how it pushes charge and what not.
 
  • #32
graycloud79 said:
the first 6V battery, does it release a current from it's positive terminal as in electrons flowing from it(+terminal) to the second battery's (9V) +terminal. that makes no sense because electrons usually flow (in the normal simple series circuit schematic i understand) from -terminal to the +terminal of the same battery.

Look up the definition of current. It is almost universally taught as the flow of positive charge . It goes backward from the electrons . It is called "conventional" because the electron wasn't discovered until after the basic laws of electricity were figured out, and the old timers thought that whatever was the "fluid" that comprised current must be positive. So they established that convention.
I cautioned earlier to stick to "conventional" current, ie positive .
In my school we had a joke: "Electric current goes backward because Ben Franklin defined it as positive. Ben was a brilliant civil engineer who designed canals and buildings. But that's what happens when you let a Civil Engineer mess with electricity."over and out
 
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  • #33
graycloud79 said:
mrsparkle is there a source website* where i can learn this? i only have a general physics I community college background.
i mean electric fields and how it pushes charge and what not.

the http://amasci.com/ele-edu.html site I recommended earlier. I recommended it because it dispels a number of myths regarding electricity. Check out the 3rd link, What is Voltage? specifically.

http://www.allaboutcircuits.com/ is another good one.
 
  • #35
in some aspects amasci can be difficult to understand.

i'm reading Electricity Experiments you can do at home by stan gibilisco for more help.
 
<h2>1. What is the difference between series and parallel voltage sources?</h2><p>In a series circuit, voltage sources are connected end-to-end, with the positive terminal of one source connected to the negative terminal of the next. This results in a cumulative increase in voltage, with the total voltage equal to the sum of the individual sources. In a parallel circuit, voltage sources are connected side-by-side, with the positive terminals connected and the negative terminals connected. This results in a constant voltage across each source, with the total voltage equal to the voltage of any single source. </p><h2>2. How does the total voltage change in a series circuit?</h2><p>In a series circuit, the total voltage increases with each additional voltage source. This is because the voltage sources are connected end-to-end, resulting in a cumulative increase in voltage. However, the total voltage will be limited by the resistance of the circuit, as the voltage will drop across each component in the circuit.</p><h2>3. How does the total voltage change in a parallel circuit?</h2><p>In a parallel circuit, the total voltage remains constant across each voltage source. This is because the voltage sources are connected side-by-side, resulting in a constant voltage across each source. The total voltage will only change if one of the sources is removed or if the circuit is opened.</p><h2>4. What happens to the current in a series circuit with multiple voltage sources?</h2><p>In a series circuit, the current remains constant throughout the circuit. This means that the same amount of current will flow through each voltage source, regardless of the number of sources present. However, the total current will be limited by the resistance of the circuit, as the current will decrease with each additional component in the circuit.</p><h2>5. How does the current change in a parallel circuit with multiple voltage sources?</h2><p>In a parallel circuit, the current is divided among the different branches of the circuit. This means that the total current will be greater than the current through any single source. The exact amount of current flowing through each source will depend on the resistance of each branch and the voltage of the source. However, the total current will always equal the sum of the individual branch currents.</p>

1. What is the difference between series and parallel voltage sources?

In a series circuit, voltage sources are connected end-to-end, with the positive terminal of one source connected to the negative terminal of the next. This results in a cumulative increase in voltage, with the total voltage equal to the sum of the individual sources. In a parallel circuit, voltage sources are connected side-by-side, with the positive terminals connected and the negative terminals connected. This results in a constant voltage across each source, with the total voltage equal to the voltage of any single source.

2. How does the total voltage change in a series circuit?

In a series circuit, the total voltage increases with each additional voltage source. This is because the voltage sources are connected end-to-end, resulting in a cumulative increase in voltage. However, the total voltage will be limited by the resistance of the circuit, as the voltage will drop across each component in the circuit.

3. How does the total voltage change in a parallel circuit?

In a parallel circuit, the total voltage remains constant across each voltage source. This is because the voltage sources are connected side-by-side, resulting in a constant voltage across each source. The total voltage will only change if one of the sources is removed or if the circuit is opened.

4. What happens to the current in a series circuit with multiple voltage sources?

In a series circuit, the current remains constant throughout the circuit. This means that the same amount of current will flow through each voltage source, regardless of the number of sources present. However, the total current will be limited by the resistance of the circuit, as the current will decrease with each additional component in the circuit.

5. How does the current change in a parallel circuit with multiple voltage sources?

In a parallel circuit, the current is divided among the different branches of the circuit. This means that the total current will be greater than the current through any single source. The exact amount of current flowing through each source will depend on the resistance of each branch and the voltage of the source. However, the total current will always equal the sum of the individual branch currents.

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