Does My Bike Induce Electricity? 72
An anonymous reader asks: "I have a steel frame road bicycle and recently began riding on a path that parallels high-tension power lines for several miles. My question is: Does my bike induce an electric current by passing through the electric fields from the power lines? I normally ride the section at about 18 miles per hour, estimate the distance to the lines at about 75-100 feet, and think they're 200KV lines."
I wouldn't think so (Score:1)
obligatory Slashdot quote reference (Score:2)
Cars (Score:2)
Re:Cars (Score:1)
Re:Cars (Score:3, Interesting)
Fun "experiment"... (Score:2)
combusting hay (Score:3, Funny)
The way he explained it, the hay on the ground built up a charge and it was just a matter of time before it discharged with the power lines. When he was stacking, he must have gotten the charged hay too close or something, and it shocked him.
I suppose it's possible you're getting a little stray charge, but as long as you're not wearing a suit made of hay...
Yes (Score:4, Funny)
No... (Score:3, Interesting)
Physics seems to provide an endless supply of April Fool's jokes!
Re:No... (Score:1)
Re: (Score:2)
Hey Taco (Score:4, Funny)
Re:Hey Taco (Score:2, Funny)
Do not set the evil bit when the stupidity bit can be set.
Dull glow? (Score:3, Funny)
Aha! (Score:3, Funny)
Now we know why they run power lines alongside every road -- so they can soak up the free energy caused by cars driving alongside them!
Re:Aha! (Score:1)
Re:Aha! (Score:3, Interesting)
Actually, the magnetic field of the AC line will induce eddy currents in the body of a passing car. These eddy currents produce their own magnetic fields which oppose the field from the wire, and these fields actually reduce the current flowing in the wire (the energy to produce the eddy current has to come from somewhere, that somewhere is the current in the wire).
The
Dorm session question (Score:2, Informative)
Re:Dorm session question (Score:3, Informative)
Yes. The current goes around in circles in the steel frame your wheels (eg arc-on-outside/radius/central-bit/radius/etc - like a pie slice). Depending on the exact configuration you might be able to power a very small light bulb from it. I wouldn't bet my hand on it though.
Daniel
Isn't this? (Score:2)
You might run an LED with it (Score:1)
My 4-stroke (Score:1)
another shocking anecdote... (Score:2, Interesting)
Re:another shocking anecdote... (Score:1)
Depends (Score:5, Interesting)
You can increase the induced emf by wrapping multiple turns of insulated magnet wire into a loop in the same orientation as the bike frame. Neglecting the finite resistivity of the wire, you will get twice as much emf every time you double the number of turns. But even with hundreds of turns we're still talking about millivolts or perhaps hundredths of a volt at most.
If the line is DC, then there will be no induced emf since the magnetic field is not changing.
The speed at which you ride the bike has no influence on the induced emf, unless you are travelling near light speed, in which case the apparent frequency of the AC will be reduced since you are "catching up" to the propagating waveform. But I don't think you could pedal that fast :-)
Re:Depends (Score:2)
But he's moving relative to the wire.
Re:Depends (Score:2)
That doesn't matter, because he's moving along parallel to the wire. The magnetic field is perpendicular to both the wire and the direction of travel, so the field strength is independent of the motion. If he were moving obliquely w.r.t. the wire then the field *would* depend on the motion and you would see an emf.
Re:Depends (Score:2)
If that's the case, AC induces, DC doesn't, then how come AC is used for long distance lines? It seems like you'd want the transmission method that *doesn't* induce current in everything near the line.
Re:Depends (Score:2)
You answered your own question. It's precisely *because* AC induces that it's used for transmission. Induction is what makes transformers possible. DC current can't be easily converted from one voltage to another the same way AC can.
The powerlines you see around your neighborhood are 12-20 kV, 50 or 60 Hz. For efficiency reasons, power is transmitted at the highest possible voltage (this reduces resistive loss)
Right Hand Rule (Score:2)
The magnetic field is perpendicular to both the wire...
Naw, the magentic field lines are found by using the "right hand rule" (or the left hand rule if you're an EE guy). So the field lines wrap around the wire. But he still isn't 'cutting' any of the lines by riding parallel to the wire (aka moving between different potential levels in the field). Just a techincal note.
neurostarRe:Right Hand Rule (Score:2)
Right, they "wrap around" the wire. Although the field lines are curling around the wire, they are still always perpendicular to it (dot product of magnetic field and current is always zero). The field lines are tangentially perpendicular, not radial.
Re:Right Hand Rule (Score:2)
Ah ok. You're correct. My bad.
neurostarAre you sure? (Score:2, Funny)
The electric field from a charge will be perpendicular to the charge. The magnetic field follows the old "right-hand rule" and circles the current. This would still imply that the field is going throught the frame of the bike but....
Clear up a few things... (Score:2, Informative)
The lower the current you send down a wire, the less energy lost due to resistance. (P=IE, E=IR, so P=R*I^2). This is a major concern over long wires, where the overall resistance can be quite high. With AC power, you can transform from high current / low volatage, to low current / high voltage, and back quite easily. So you can put your powerplant far away from the consumer. However with DC, you can't do
Re:Clear up a few things... (Score:1)
Re:Clear up a few things... (Score:1)
Re:Clear up a few things... (Score:2)
I believe this is possible, but this wasn't caused by induction. The induced emf due to the transmission wire's magnetic field will create a current in the bike frame, but this current is just a loop, and can't cause charge to build up on the bike.
What happened to you was an effect of the
Re:Depends (Score:2)
I could have used your post for the key too.
Re:Depends (Score:1)
There would indeed be some current in the bike. IF you actually used it, though, causing a power drain, you would be stealing power from the power company, and probably labeled a terrorist
Re:Depends (Score:2)
Ok, then what is this [hydro.mb.ca] and this [siemens.com] and this [nexans.no] and this [fujikura.com] and this [stantec.com]?
An Interesting Incident (Score:3, Interesting)
I was once exiting a movie theater in a drizzle. This particular theater's parking lot is under high-tension transmission lines. Since it was raining, I was using an umbrella.
Walking across the parking lot, I heard a buzzing sound. Looking up, I noticed that where the metal ribs of the umbrella connected to the plastic hub in the center, that the tips of the ribs were arcing between them!
Surprisingly enough, I merely thought it curious and noted that I should go back some time and study the effect further and take some measurements, etc. That was probably a dozen years ago, and I pretty much forgot about it until this story prodded my memory.
I assume that some sort of "Tesla" effect was responsible, as I felt nothing myself. I don't know the specifics of the transmission lines involved.
Re:An Interesting Incident (Score:2)
Mmmm... rib tips.
(C'mon, it's more on-topic than all the dupe complaints today
It's in the FAQ (Score:2)
I had this happen too. Try less 'shrooms and more Kool Aid next time you see The Wall at the $1 theater.
probably, but not very much (Score:2, Informative)
alright, I'm a long way from being an EE, but I remember my high-school physics pretty well.
a magnetic field will form in concentric rings around any conductor that's carrying current, and the strength of that magnetic field will be proportional to the amount of current flowing through the conductor, and will drop off sharply with distance.
now, currents are only induced by a changing magnetic field, and the current will be proportional to the change in magnetic field strength. so if the power lines were c
Re:probably, but not very much (Score:2)
How much energy could you extract from these powerlines using a device which you could carry with you while walking on the ground below them? Would it be enough to power an LED like you see on some cell phone antennas? More? Less?
Re:probably, but not very much (Score:2)
In theory yes (Score:2, Interesting)
Re:In theory yes (Score:1)
200kV @
12V @ 200A = 2400W
But your premise is false.... stepping up the voltage does not reduce the amount of power available.. it remains constant (barring loss due to to other stuff). And those high voltage transmission lines have a lot more power than the low voltage in your house, as they are later broken down into smaller, lower voltage, lower power chunks for different homes.
It's not the inducer, it's the inducee (Score:2)
Not so much induce as have induced in it. Your bicycle's steel frame, an electro-magnetic conductor, could have a current induced in it if it is in motion relative to a magnetic field( field stationary, bike moving, bike stationary, field moving). Because the field is expanding and collapsing at 60 cycles per second it would be in motion relative to your bike whether your bike is moving parallel to the po
Yes, but it's negligible (Score:4, Informative)
Yes and if that guy with the barrels full of... (Score:3, Interesting)
It doesn't matter. (Score:1)
Don't forget it's a three-phase line (Score:1)
Grounding (Score:1)
Re:Grounding (Score:1)
It will, but it's not a huge deal. (Score:2)
Not just the power lines, the earth's field too. (Score:2)
The current is negligable, but it's there.
So, by moving through the Earth's field you'll be inducing a voltage, but it's going to be extremely small.