# Tree Branch on Wires: Discuss Strange Arc & Effect

• Bassalisk
In summary: I mean, my neighbor still has my Jacob's Ladder. :wink:In summary, a group discusses a video of an electric arc going upwards between power lines and speculates on the cause of this phenomenon. They consider the effects of convection, Lorentz force, and heated air, and share memories and experiences with similar arcs. They also discuss another video showing intentional arc creation and the limitations of certain switches.

#### Bassalisk

g4ph-h7l_aM[/youtube] This is pret... appear at all? Can we discuss this effect?

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you're tapping my oldest memory banks now.

when i was a kid had a next door neighbor hwo was a sort of Sorcerer's Apprentice, making Jacob's Ladders and the like.

I think you'll find the arc went up by simple convection like the smoke did. The ionized air is very hot...

there is a force on the charge that is moving through the arc, Q X Velocity (cross) B
but shouldn't that twist the arc parallel to conductors?
i didn't notice that in the video..

old jm

jim hardy said:
you're tapping my oldest memory banks now.

when i was a kid had a next door neighbor hwo was a sort of Sorcerer's Apprentice, making Jacob's Ladders and the like.

I think you'll find the arc went up by simple convection like the smoke did. The ionized air is very hot...

there is a force on the charge that is moving through the arc, Q X Velocity (cross) B
but shouldn't that twist the arc parallel to conductors?
i didn't notice that in the video..

old jm

I think I understand. (ion part)

But this is AC, how does lorentz force apply to this when we have alternating B field.

At least I see it like so.

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Bassalisk said:

This is pretty old but it just crossed my mind. Wanted to share it with you guys.

One question though, why is that current arc going upwards? And why did it appear at all?

Can we discuss this effect?

Tree branch "falls" on power lines? From nowhere on a relative wind-free day with cameras ready? Admit it, you threw it up there didn't you?

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gnurf said:
Tree branch "falls" on power lines? From nowhere on a relative wind-free day with cameras ready? Admit it, you threw it up there didn't you?

:D I live nowhere near power lines anyway(city). But even I wanted to, chances of me putting that branch precisely that way are almost none :D

But if I did have a chance to do it, I won't lie to you and tell you that I wouldn't :rofl:

""""But this is AC, how does lorentz force apply to this when we have alternating B field."""

B alternates certainly, and so does Velocity (current in the arc is alternating )

i think you're right - if i remember how to cross vectors, the result also alternates direction hence nets to zero... mumble mumble...c'mon old brain,,, V X B--- rotate V into B and result is direction a right hand thread would move?

was hoping youd reaffirm my old memory because i don't have my books handy. (visiting friends away from home)

am i right , my kind friend?

jim hardy said:
""""But this is AC, how does lorentz force apply to this when we have alternating B field."""

B alternates certainly, and so does Velocity (current in the arc is alternating )

i think you're right - if i remember how to cross vectors, the result also alternates direction hence nets to zero... mumble mumble...c'mon old brain,,, V X B--- rotate V into B and result is direction a right hand thread would move?

was hoping youd reaffirm my old memory because i don't have my books handy. (visiting friends away from home)

am i right , my kind friend?

Ahh crossing vectors? your index finger points in the direction of the first component, your middle finger points in the direction of the second component, your thumb is showing crossed vectors.

Is this what you are looking for?

Maybe the flow of power has something do with it? Flow of active power is in one direction

This old video shows what it looks like when transmission line phases arc.

dlgoff said:
This old video shows what it looks like when transmission line phases arc.

Yes yes I know this one! I was completely baffled when I first saw this :D

i think the Q V cross B forces are making the arc 'corkscrew"

and simple bouyancy of heated air is driving it upward

but I'm going from old memories here and need corroboration from freshman physics.

and yes Bassalisk that's what i was looking for... step 1 toward that corroboration

memory - i can almost remember when i had one...

jim hardy said:
memory - i can almost remember when i had one...

hahahahahaha this really made me laugh ! :rofl:

I will investigate this further. It does make sense that the heated air goes up. After that I have to find out why does it go to the right. (along the wires) why not simply stay in place. This probably has something to do with the effect of jacob's ladder.

that last video is intentional opening of a disconnect switch in that yard. first second you can see it swing away... that kind of switch cannot interrupt load current, but the simple charging current makes a plenty impressive arc.

so judging by lack of excitement by participants that video, the current was pretty small. i didnt notice molten metal falling...

jim hardy said:
that last video is intentional opening of a disconnect switch in that yard. first second you can see it swing away... that kind of switch cannot interrupt load current, but the simple charging current makes a plenty impressive arc.

so judging by lack of excitement by participants that video, the current was pretty small. i didnt notice molten metal falling...

Yea but still its an amazing to see that much current scaled up! Before this video I only witnessed sparks. Or group of many sparks in best case.

That video of electric power plant switch thingy really made me stare.

jim hardy said:
when i was a kid had a next door neighbor hwo was a sort of Sorcerer's Apprentice, making Jacob's Ladders and the like.
Maybe I was your neighbor. I've still got my 9KV neon sign transformer.

power side of EE is to me more interesting than computers.

i honestly considered programming but decided it's more fun to magnetize iron by the ton than by the micron.

i was happy with DOS and QBASIC.

but that's just me.

old jim

EDIT Don keep those treasures. you never know when you'l influence somebody ! my life is richer for those memories of Mr Gaunt's garage ...

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jim hardy said:
power side of EE is to me more interesting than computers.

i honestly considered programming but decided it's more fun to magnetize iron by the ton than by the micron.

i was happy with DOS and QBASIC.

but that's just me.

old jim

I would go for electro-energetics too, if I had more access to such devices in my youth. But since I was sitting in front of computer longer than I wasn't, I went for electronics. I see by these synchronous machines, transformers... from my fundamentals of electro-energetics systems course, that there are a LOT of things that tingle my interest.

Just, all this reactive power, etc when I couldn't understand it at first, and when I fell in love with transistor, I went for electronics.