(basic question) why is current the same in series connection.

[Pastory]

(basic question) why is current the same in series connection. An explanation in 3d video would be very helpful

 

[marconi]

The current is the same through a surface (ie 2D plane) cut transverse to the linear axis of an electrical conductor anywhere along the conductor because the force on each of the charge carriers - electrons - is always parallel to the direction of the electric field in the conductor ie: normal to the transverse surface plane. The direction of the electric field in a conductor is parallel to the length or linear axis of the conductor. All electrons can only move in one direction in the conductor determined by the direction of the electric field. (Actually the electric model is that electrons drift at a surprisingly slow speed).

The electric field strength E, measured in Volts per meter, has a constant strength along the the conductor. The force on each electron is F = E x e where e is the charge of a single electron. So, all electrons experience the same force wherever they are in the conductor - none is treated differently.

For the current not to be the same in a circuit made up of conducting elements would require electrons to be subject to forces which are at a right angle to the axis of the conductor. This would require an electric field at right angles to the linear axis of the electric conductor. In normal circuits this does not exist. Thus there is no electrodynamical force at work at any transverse plane along the conductor to stop some or all electrons moving linearly along the axis of the conductor and instead forcing them in a transverse direction which would thereby reduce the effective linear current after the location of the transverse plane to cause the current not to be the same at any location.

For you: If there was a transverse electric field where would some electrons go? And then what would happen or exist?

Good question by the way

ps1: I have had three glasses of wine so I hope the above makes some sense if not complete sense!

ps2: Or you could just say the law of conservation of charge/Kirchhoff's first law.

 

[Pastory]

The current is the same through a surface (ie 2D plane) cut transverse to the linear axis of an electrical conductor anywhere along the conductor because the force on each of the charge carriers - electrons - is always parallel to the direction of the electric field in the conductor ie: normal to the transverse surface plane. The direction of the electric field in a conductor is parallel to the length or linear axis of the conductor. All electrons can only move in one direction in the conductor determined by the direction of the electric field. (Actually the electric model is that electrons drift at a surprisingly slow speed).

The electric field strength E, measured in Volts per meter, has a constant strength along the the conductor. The force on each electron is F = E x e where e is the charge of a single electron. So, all electrons experience the same force wherever they are in the conductor - none is treated differently.

For the current not to be the same in a circuit made up of conducting elements would require electrons to be subject to forces which are at a right angle to the axis of the conductor. This would require an electric field at right angles to the linear axis of the electric conductor. In normal circuits this does not exist. Thus there is no electrodynamical force at work at any transverse plane along the conductor to stop some or all electrons moving linearly along the axis of the conductor and instead forcing them in a transverse direction which would thereby reduce the effective linear current after the location of the transverse plane to cause the current not to be the same at any location.

For you: If there was a transverse electric field where would some electrons go? And then what would happen or exist?

Good question by the way

ps1: I have had t7hree glasses of wine so I hope the above makes some sense if not complete sense!

ps2: Or you could just say the law of conservation of charge/Kirchhoff's first law.

Sorry for another extra question; Suppose bulbs (incandescent) of different resistances are connected in series, will their brightness be the same?

 

[Pastory]

So, all electrons experience the same force wherever they are in the conductor - none is treated differently

How can the electrons in the proceeding resistors (component) experience same force while there's a voltage drop at each of the resistor in series connection, or what does voltage drop really mean - I used to think voltage drop is the decrease in the pushing force of electrons and I still do, clarify to me on this one.

 

[marconi]

Sorry for another extra question; Suppose bulbs (incandescent) of different resistances are connected in series, will their brightness be the same?

No.

 

[marconi]

How can the electrons in the proceeding resistors (component) experience same force while there's a voltage drop at each of the resistor in series connection, or what does voltage drop really mean - I used to think voltage drop is the decrease in the pushing force of electrons and I still do, clarify to me on this one.

My explanatory model was for a current in a uniform, homogeneous wire/conductor in which the electric field along its length is uniform in intensity.

If you introduce discrete resistors into the circuit loop the force in each resistor depends on the strength of the electric field within them. The electric field in a resistor is a function of the voltage drop across the resistor and the length of the resistance path taken by the electrons inside the resistor. The voltage drop across each resistor depends on the electromotive force acting in the circuit of resistors and wires in series. This emf divides across the resistances in the ratio of their resistances.

The force on each electron varies with E which in turn depends on voltage drop/electron's path length. So the pushing force Ee depends on the potential difference or voltage drop(V) and distance(d) between the ends of each resistor (V/d x e). The pushing force on each electron changes to maintain the same current flow (rate of flow of charge) wherever it takes place in the circuit. This is Nature's conservation of energy law/Kirchhoffs second law at play.

Higher E = V/d (voltage drop/path length) implies higher pushing force on each electron within the resistor. The actual pushing force is due to the electromotive force in the circuit which sets up electric fields in each resistance. Electrons interact with the electric field and experience a force which moves them in the direction of the field from high potential to low potential - in the direction of the voltage drop.

Voltage drop is not the decrease in the pushing force. The voltage drop between two points is an indicator of the strength of the electric field between those points. The actual strength of the electric field depends also on the distance between those two points and not just the voltage/potential difference. The pushing force on an electron as at moves between these two points depends then on the strength of the electric field between them; thus for constant distance between these points as is the case in a resistor higher voltage drop means higher electric field and higher force on each electron.



(Or something like this!).

 

[marconi]

Pastory - greetings from London. Could you say a little more about why you have these questions? At what level are you studying electricity? If I have a self-criticism I am well aware of is that I often assume too much knowledge of mathematics and physics, two of my favourite subjects. After a while in advanced study in engineering or physics one relies on the language of mathematics rather than 'pictures or films' of what is happening so returning to a picture or film is good. Do you have a picture or film in your mind - your mental model of how a current made up of moving electrons move in a conductor? I have given you some insight into mine. The flow of current in conductors is actually a very difficult topic so I ought to declare my models may be out of date but not necessarily useless in gaining some understanding or being able to make predictions.

Two pieces you might enjoy:

What is the speed of electricity? - https://www.wtamu.edu/~cbaird/sq/2014/02/19/what-is-the-speed-of-electricity/#:~:text=The%20individual%20electron%20velocity%20in,a%20trillion%20kilometers%20per%20hour.

Microscopic View of Electric current - http://hyperphysics.phy-astr.gsu.edu/hbase/electric/miccur.html

 

[Pastory]

No.

Why then, won't they have the same brightness?

 

[Pastory]

Pastory - greetings from London. Could you say a little more about why you have these questions? At what level are you studying electricity? If I have a self-criticism I am well aware of is that I often assume too much knowledge of mathematics and physics, two of my favourite subjects. After a while in advanced study in engineering or physics one relies on the language of mathematics rather than 'pictures or films' of what is happening so returning to a picture or film is good. Do you have a picture or film in your mind - your mental model of how a current made up of moving electrons move in a conductor? I have given you some insight into mine. The flow of current in conductors is actually a very difficult topic so I ought to declare my models may be out of date but not necessarily useless in gaining some understanding or being able to make predictions.

Two pieces you might enjoy:

What is the speed of electricity? - https://www.wtamu.edu/~cbaird/sq/2014/02/19/what-is-the-speed-of-electricity/#:~:text=The%20individual%20electron%20velocity%20in,a%20trillion%20kilometers%20per%20hour.

Microscopic View of Electric current - http://hyperphysics.phy-astr.gsu.edu/hbase/electric/miccur.htm

Marcon, I am very grateful for your generous kindness and unending empathy to my may be boring questions (may be because I want to understand these things profoundly and really insightfully). I completed my A-level education seven years or so ago and I was taking PCM (physics chemistry mathematics) but couldn’t go on with university studies due to health problems.
Since when I was in Ordinary level secondary school I was very confused with how electricity works and was very curious to know that especially in it's very profound working but couldn’t get someone or something to give me those profound insights about charges and wires and everything in electricity, so I kept memorizing theories and formulas untill now but cannot correctly twist those theories in a logical electrical basis. But now I just am an electricity DIY.
Here therefore after reaching you, I hope I can become an expert in electricity.
This is Pastory Kimaryo from
East Africa in Tanzania.

<NUMBER REMOVED>, this is my WhatsApp number, we can chat via whatsapp for easiness.
I believe that if you teach me in a sense to make me understand these stuffs insightfully, you are going to cement your knowledge and understanding a hundred times.

Thanks.

 

[marconi]

Why then, won't they have the same brightness?

Because the lower the resistance of the lamp filament the lower is the struggle of each electron to flow in the filament from one end of the filament to the other. Less of each of the electron’s potential energy is converted into the electron’s kinetic energy. Thermal or heat energy is what is required for the filament to glow and be bright. It is the vibration of atoms which is heat energy. The atoms vibrate because moving electrons collide with them. The electrons move because they experience a force in the electric field which accelerates them. In a lower resistance there are fewer collisions or less of a struggle. Or in other words the electric field interacting with each electron charge does less mechanical work.

The energy transfers are electrical to mechanical to heat and light.

 

[marconi]

https://www.ehow.com/how-does_5202436_filament-connecting-wires-do-not_.html

Here is a similar explanation.

 

[Pastory]

Because the lower the resistance of the lamp filament the lower is the struggle of each electron to flow in the filament from one end of the filament to the other. Less of each of the electron’s potential energy is converted into the electron’s kinetic energy. Thermal or heat energy is what is required for the filament to glow and be bright. It is the vibration of atoms which is heat energy. The atoms vibrate because moving electrons collide with them. The electrons move because they experience a force in the electric field which accelerates them. In a lower resistance there are fewer collisions or less of a struggle. Or in other words the electric field interacting with each electron charge does less mechanical work.

The energy transfers are electrical to mechanical to heat and light.

Ok, now with different brightness, will the current be the same, because I just was thinking curiously that if bulbs illuminate with different levels of brightness then the currents within each of them are different then explain something to me, that current may be the same but with different brightness because of different resistances.

 

[Pastory]

https://www.ehow.com/how-does_5202436_filament-connecting-wires-do-not_.html

Here is a similar explanation.

This is of no problem to me, my main problem is with the flow of electricity in circuits.

 

[Pastory]

Sorry for this weird question, as it is electrically advised not to touch the live wires with bear hands as it will cause shock to even death, suppose I am having a circuit below (picture below) with a cell of let's say 5 volts and lick the end of the wire B, will I feel some shocks (even minimal shocks). And licking end of wire A will I not feel anything as it is a neutral wire?

 

[SparkyChick]

@Pastory ,

I've edited the post you made that included your phone number. We advise against posting such details publicly. You should be able to send @marconi a direct message by viewing his profile and clicking the 'Start Conversation' button. This would be a private conversation between the two of you unless you invite others to it.

Regards

SC

 

[marconi]

Hello again. Staying with the 3 different lamps in series, I think it would be helpful to you to understand the relationship between electromotive force(emf), current and resistance in a very simple circuit of one resistor connected across a battery.

Then move on to two resistors of the same value connected in series across the same battery and finally three of them in series.

Once you have a good understanding of emf, voltage drop, current in these circuits you are well equipped to look at two different resistors connected in series across a battery and then three different resistors in series. Three different lamps in series connected a cross a battery is similar to three different resistors.

Take a look at this tutorial on series circuits:

Physics Tutorial: Series Circuits - https://www.physicsclassroom.com/class/circuits/Lesson-4/Series-Circuits

Here is another explanation in a little more depth on how electricity flows in a conductor like a metal:

Why do electrons flow? - https://www.edinformatics.com/math_science/why-do-electrons-flow.html

Have you noticed that good conductors of electricity are usually good conductors of heat eg copper? And poor conductors of electricity are also poor conductors of heat eg polystyrene. Why do you think this is? Think about it before looking at:

https://byjus.com/questions/why-are...llent conductor,of the interacting metal ions.

And because I am curious to know what is the town or city you live in? Do not post your address, phone number or email.

 

[marconi]

Ok, now with different brightness, will the current be the same, because I just was thinking curiously that if bulbs illuminate with different levels of brightness then the currents within each of them are different then explain something to me, that current may be the same but with different brightness because of different resistances.

I have edited what you wrote above into this:

If bulbs illuminate with different levels of brightness and the currents within each of them are the same because the bulbs are in series, then they shine with unequal brightnesses because of their different values of electrical resistance to the flow of the common series current. Bulbs/lamps rely on the heating effect of a current as it flows through resistance, The heating effect of a current is called Ohmic heating (or sometimes but less often Joule heating). Thus in a series circuit the brighter lamps have higher relative resistance to the dimmer ones.

 

[Pastory]

Hello again. Staying with the 3 different lamps in series, I think it would be helpful to you to understand the relationship between electromotive force(emf), current and resistance in a very simple circuit of one resistor connected across a battery.

Then move on to two resistors of the same value connected in series across the same battery and finally three of them in series.

Once you have a good understanding of emf, voltage drop, current in these circuits you are well equipped to look at two different resistors connected in series across a battery and then three different resistors in series. Three different lamps in series connected a cross a battery is similar to three different resistors.

Take a look at this tutorial on series circuits:

Physics Tutorial: Series Circuits - https://www.physicsclassroom.com/class/circuits/Lesson-4/Series-Circuits

Here is another explanation in a little more depth on how electricity flows in a conductor like a metal:

Why do electrons flow? - https://www.edinformatics.com/math_science/why-do-electrons-flow.html

Have you noticed that good conductors of electricity are usually good conductors of heat eg copper? And poor conductors of electricity are also poor conductors of heat eg polystyrene. Why do you think this is? Think about it before looking at:

https://byjus.com/questions/why-are-metals-good-conductors-of-electricity/#:~:text=Metals are an excellent conductor,of the interacting metal ions.

And because I am curious to know what is the town or city you live in? Do not post your address, phone number or email.

Thank you for all of this

 

[marconi]

Sorry for this weird question, as it is electrically advised not to touch the live wires with bear hands as it will cause shock to even death, suppose I am having a circuit below (picture below) with a cell of let's say 5 volts and lick the end of the wire B, will I feel some shocks (even minimal shocks). And licking end of wire A will I not feel anything as it is a neutral wire?
View attachment 95663

First, never place any electrical wires in your mouth. Promise me?

The way to look at the circuit you drew is to consider whether a complete circuit is made when you touch one and only one of the wires from the battery. The answer of course is it is not a completed circuit. Therefore the electromotive force of the battery cannot set up and electric field in the wires which would cause electrons to flow from the - end of the battery to the + end of the battery. If no electrons flow then there cannot be an electric shock or sensation.

The answer above becomes not so true as the electromotive force of the battery is increased. This is because even though it may seem a circuit is not completed there may be stray connections through the air gaps for example if the air is moist. Even though the effective resistance of the electrical circuit path through the air gap may be quite high in value, as the electromotive force is increased so does the current since from Ohm's Law the current through a resistor is proportional to the voltage drop across the resistor and inversely proportional to the resistance. The resistance of the path through the gap also reduces as it shortens in distance. Thus there is an emf which when it exists across an air gap will force a current to flow the magnitude of which increases with emf and shortening of the gap. At a high enough emf the air will begin to ionise leading to a corona discharge, sparking or full on arcing.

The situation is made worse when the emf is an alternating current. This is because not only is there an effective resistance path there is also stray capacitance between the ends of the gap. A so-called capacitive current will flow in addition to the current through the stray resistance. One should keep well away from live conductors.

The term neutral only applies to a conductor when it is connected to the earth or ground by an earth electrode. The term neutral means the conductor is 'tied' to the potential of the (local) earth which means there is no potential difference between the neutral conductor and the local earth. If there is no potential difference there can be no current flow through a conducting item connected between the neutral and earth provided that one remains near to the earth electrode. Further away from the electrode other things begin to happen which are beyond your scope for now.

If you use a a figure of 50V for ac or dc as the maximum safe touch voltage in dry conditions you will remain unhurt or alive in most circumstances but this voltage may well be much lower if for example your skin is wet or the water is salty or there is a large surface area in contact across the emf.

These links take you to some articles and introduce the SELV and PELV power supplies used in the UK and Europe.
PELV | PULS - https://www.pulspower.com/uk/support/service/glossary/index/read/pelv/#:~:text=PELV%20(Protective%20Extra%20Low%20Voltage,protection%20must%20still%20be%20provided.
SELV | PULS - https://www.pulspower.com/uk/support/service/glossary/index/read/selv/#:~:text=The%20voltage%20of%20a%20SELV,exceeded%20for%20longer%20than%20200ms.

Alternating Current or Direct Current? | Which is Safer? - https://electricalinstallationservices.co.uk/alternating-current-or-direct-current/

Ohm’s Law (again!) | Electrical Safety | Electronics Textbook - https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/ohms-law-again/

 

[Pastory]

@Pastory ,

I've edited the post you made that included your phone number. We advise against posting such details publicly. You should be able to send @marconi a direct message by viewing his profile and clicking the 'Start Conversation' button. This would be a private conversation between the two of you unless you invite others to it.

Regards

SC

Sorry for some litle question, are you the moderator of this forum?