Hi
I'm newby to this forum & being confused about this article.
https://www.allaboutcircuits.com/textbook/direct-current/chpt-1/conventional-versus-electron-flow/
If the real direction of the current in dc circuit based on electron flow is from negative to positive in circuit,
Why contact of a body part with positive wire of a dc source can cause an electrical shock (while negative side of a source have excessive electrons that might pass from body toward ground)?

 

Thankfully I can get the first word in here...

Now just because you read something on the interwebs doesn't make it so. “Electron flow” is an unscientific concept based on several misunderstandings.

It is true that in most things you come across using wires and such electrons flow from a negative potential to a more positive potential. But guess what, that means the current, as defined by the International Standard of Units (French: Système international: abbreviated as SI) which is the standard all scientific work defines current as the flow of positive charges past a point.

Now when you have negative charges moving in the opposite direction you have a negative times a negative so you once again get a positive current in the opposite direction as the charge carriers (electrons).

If you go ahead and assume you can call “electron flow” as a positive current in the reverse direction you still get answers that are correct in magnitude, and the sign isn’t of much consequence. Other phenomena are not as forgiving, such as induced magnetic fields.

Unfortunately, those who wrote the textbook behind this forum did not understand this concept. They may be forgiven as they are under the misapprehension their way is better. That is incorrect, though we can still be polite to them and treat them as we do to those less fortunate that us.

I will even admit them as guests into my home, as long as they do not make and messes on my couch or chairs.

As far as touching either a positive potential or a negative one, either will just as reliably give you a shock or kill you. This is because if you complete a circuit current can either flow out of you to the negative terminal, or into you from the positive terminal.

You may feel free to reverse those directions and speak of electrons, but in a very real sense I just said that same thing by choosing the term current.

 

You can experience an electrical shock if you touch a high voltage source regardless of the polarity of the source and the polarity of the charge carrier.

How fast do electrons move in a circuit?
The speed of electrons in a circuit is of the order of 0.0002 metres per second.
It doesn't matter whether electrons are entering or leaving the human body.

Electricity experienced in the body is electrons moving a fraction of a centimetre from one location to another. If this electrical current happens across a critical part of the body such as your heart, your life or health is compromised.

 

Thank you MrChips.
Touching a wire that connected to a negative dc source such as batteries in series or rectifier, could it cause a problem?
I think contact to a positive side of a source canbe problematic.

 

Thank you MrChips.
Touching a wire that connected to a negative dc source such as batteries in series or rectifier, could it cause a problem?
I think contact to a positive side of a source canbe problematic.

I said it makes no difference touching positive or negative terminal.

 

For the current to flow, the circuit has to be completed.
If the negative is grounded, and you are standing on the ground or connected to the ground, then touching the negative terminal will not give a shock and the positive terminal WILL!
If you are isolated, and you will not get a shock whether you touch the positive or negative terminal.

 

For the current to flow, the circuit has to be completed.
If the negative is grounded, and you are standing on the ground or connected to the ground, then touching the negative terminal will not give a shock and the positive terminal WILL!
If you are isolated, and you will not get a shock whether you touch the positive or negative terminal.

Be careful here.
Don't say this to the high voltage linesman as he is being dropped off by helicopter on to a high voltage transmission line.

 

Oh for goodness sake, how many times do we have to go through this. My standard is that current flows positive to negative.Thats how components are marked(diodes etc.) And yes I know that electrons flow the other way but for most purpose it don't matter.
Yes I have seen the high voltage worker etc. and yes he picks up a static charge but it don't kill him even at that voltage.

 

Oh for goodness sake, how many times do we have to go through this. My standard is that current flows positive to negative.Thats how components are marked(diodes etc.) And yes I know that electrons flow the other way but for most purpose it don't matter.
Yes I have seen the high voltage worker etc. and yes he picks up a static charge but it don't kill him even at that voltage.

How many times? My guess is every time a new enthusiast ask the question, that just being a rough guess on my part. So with new inquisitive people coming up every day you can figure on getting asked pretty frequently. The good news is there is no rule which says you need to reply every time the question is asked.

Me? I learned current flow was negative to positive, it was how it was taught and presented to me. That got me through 45 years and then some. Never really mattered unless you really get into the physics or chemistry of things. As to electrical shock? I suggest you try real hard to avoid it as it can range from uncomfortable to making you quite dead which is likely to ruin your day. During electrocution I doubt you will have any concerns if the current flow is conventional current flow or electron current flow. That said you may find it interesting to Google Conventional verse Electron current flow. Read till your head hurts or explodes and then don't look back.

Ron

 

Thank you all.
But if you touch or even put your hand near the spark plug wire that's disconnected from the plug, you maybe experience the electrical shock although the automotive has been isolated form ground via rubber wheels.
Also it seems the spark direction is from the centre electrod to the body of spark plug. (From positive to negative)

 

Reloadron, Yes well as they say , horses for courses, Maybe cos its on the other side of the globe our current CONVENTION is positive to negative, unless as you say we need to deal with the physics or chemistry. Been using that for over 58 years and has never led me astray.
Shocked, I don't get shocked much by anything let alone electricity. Only ever got kicked by it once while doing HI-pot testing. Only other times its usually static charge on carpet etc, or car seats.

 

But if you touch or even put your hand near the spark plug wire that's disconnected from the plug, you maybe experience the electrical shock although the automotive has been isolated form ground via rubber wheels.

If you go back to post #7 and watch the video the helicopter is not grounded and yet when the rod connected to the helicopter it draws an arc. Why? When I walk across a wool rug in the winter and reach for a door knob which is not grounded I draw an arc, why? More specific what does the rod extended from an ungrounded helicopter draw that arc? Got any ideas?

Ron

 

Reloadron, Yes well as they say , horses for courses, Maybe cos its on the other side of the globe our current CONVENTION is positive to negative, unless as you say we need to deal with the physics or chemistry. Been using that for over 58 years and has never led me astray.
Shocked, I don't get shocked much by anything let alone electricity. Only ever got kicked by it once while doing HI-pot testing. Only other times its usually static charge on carpet etc, or car seats.

Horse of another color?

I guess my point was how much does it matter. I have seen the question beat to death (not to be confused with beating a dead horse) and looking back at an entire career it never really mattered what the direction of current flow was. Learned it one way and then another...

Having been at it a good number of years you may have shared this experience. Working with a young newly hired engineer and one of our brightest we were tossing a partial penciled circuit around on my dest on a sheet of paper. I used a reference to E as in E = I * R. Finally he looked up at me and quizzically asked why I kept using a letter E when it should be a V for voltage. I thought about it, smiled and told him I had been using E representing a unit of Electromotive Force my entire life and a year before retiring I wasn't about to change it. I guess V = I * R would be correct but the answers will always be the same. He obviously know where I placed an E he saw the V. Not worth getting pedantic about is how I see things.

Ron

 

Thank you all.
But if you touch or even put your hand near the spark plug wire that's disconnected from the plug, you maybe experience the electrical shock although the automotive has been isolated form ground via rubber wheels.
Also it seems the spark direction is from the centre electrod to the body of spark plug. (From positive to negative)

Positive or negative - it doesn't matter.

Look carefully at the man on the high voltage line.
He and the helicopter are obviously isolated from earth ground. Yet we see huge sparks from his grounding rod.

He is wearing a special white suit. This is not to protect him from rain or from bird poop.
Why do you think he is wearing this white suit?

 

Your body is a bag of salt water. Your body is full of separated charges and ions......both negative and positive.

So any potential........will conduct current.

 

Electron flow is from negative to positive in a circuit.
Electron flow is from positive to negative inside a battery feeding the circuit.

The conventional current flow is ficticious, arbitrarily defined from positive to negative inside a circuit, and that is a convention, not a fact. Current is the flow of electrical charge carriers.

Long interesting reading ----> http://amasci.com/miscon/whatis.html
With a bunch of links within, like :----> http://amasci.com/miscon/eleca.html#cflow

 

Your body is a bag of salt water. Your body is full of separated charges and ions......both negative and positive.

So any potential........will conduct current.

Is this the only reason?
What about the direction of current flow?

 

Your body is a bag of salt water. Your body is full of separated charges and ions......both negative and positive.

So any potential........will conduct current.

Is this the only reason?
What's about the direction of current flow?

 

If the real direction of the current in dc circuit based on electron flow is from negative to positive in circuit,
Why contact of a body part with positive wire of a dc source can cause an electrical shock (while negative side of a source have excessive electrons that might pass from body toward ground)?

You're obsessing over something that doesn't matter as long as you're consistent in the assumed direction.

Current actually flows from negative to positive because current is made up of electrons. Before that was known, current was assumed to flow the other direction.

Either direction will work as long as you're consistent. Some text books use electron current and others use conventional current.

Current direction doesn't matter when you're talking about electrical shock. All that takes is a voltage differential sufficiently high for the effect to be felt. It doesn't matter which "terminal" is at a higher or lower potential; all it takes is a difference in potential.

 

Doesn't mater except in particle accelerators (like cathode ray tubes).