researchers have now found that a vehicle's magnetic field has an inverse relationship with distance at small distances.

I'm pretty sure that relationship is valid at all distances.

What your new car might look like.

Wasn't this figured out years ago in making magnetic proximity sensors so Russian bombers couldn't jam the missiles which had used radar proximity sensors.

Exception Collection: They only just now figured out that the inverse-square law applies to cars?

Careful with the wording here folks. They're saying they've found an inverse relation with distance, not distance squared. Remember, magnetic monopoles (probably) don't exist, so you don't have any of the nice, outward pointing linear field lines, like those you see when you draw electric fields surrounding a charged particle. Since mag field lines have to start and terminate at the car, they'll bend, twist, and weave around the vehicle; usually in less-than-predictable patterns.

In the far zone, (i.e., the nearest car in front of you is a small dot on your windshield) then your fields obey inverse-square laws pretty well. But in the near zone, as is being discussed for collision avoidance, all hell can break loose.

Recall this example from your college days. In this example, the field from the wire will always be related to the distance rather than the distance squared. However you need to make a couple "ideal" assumptions; like the not-insignificant assumption that the wire is of infinite length.

In the real world, generally speaking, you get a bit of a cross between the two. If you're close enough to any wire, regardless of shape, you get a field relation closer to, though not exactly, 1/r. When you're sufficiently far away, you get a field relation closer to, but again not equal to 1/r^2.

From the actual article, these guys are deriving a near zone relationship for two approaching vehicles. Before final near-zone approximations, the relation formula actually looks like this:



they then kill a few terms and finally end up with this.



But yes, that m_o term is actually directly dependent on volume, so there will definitely have to be considerations for differently sized vehicles.

Flt209er: Exception Collection: They only just now figured out that the inverse-square law applies to cars?

Careful with the wording here folks. They're saying they've found an inverse relation with distance, not distance squared. Remember, magnetic monopoles (probably) don't exist, so you don't have any of the nice, outward pointing linear field lines, like those you see when you draw electric fields surrounding a charged particle. Since mag field lines have to start and terminate at the car, they'll bend, twist, and weave around the vehicle; usually in less-than-predictable patterns.

In the far zone, (i.e., the nearest car in front of you is a small dot on your windshield) then your fields obey inverse-square laws pretty well. But in the near zone, as is being discussed for collision avoidance, all hell can break loose.

Recall this example from your college days. In this example, the field from the wire will always be related to the distance rather than the distance squared. However you need to make a couple "ideal" assumptions; like the not-insignificant assumption that the wire is of infinite length.

In the real world, generally speaking, you get a bit of a cross between the two. If you're close enough to any wire, regardless of shape, you get a field relation closer to, though not exactly, 1/r. When you're sufficiently far away, you get a field relation closer to, but again not equal to 1/r^2.

From the actual article, these guys are deriving a near zone relationship for two approaching vehicles. Before final near-zone approximations, the relation formula actually looks like this:

[apl.aip.org image 640x43]

they then kill a few terms and finally end up with this.

[apl.aip.org image 333x33]

But yes, that m_o term is actually directly dependent on volume, so there will definitely have to be considerations for differently sized vehicles.

That was the best explanation of anything I've ever seen on fark.

+100 and keep up the good work.

Exception Collection: Though I do intend to take a PE-Electrical exam at some point in the distant future (well, OK, 2015 - SE will be 2012, GE will be 2013, ME will be 2014).

Right on. And yeah, this stuff probably won't ever bother you in your professional career. Good luck on your exams; though I get the feeling you'll do fine.

SquishyLizard: That was the best explanation of anything I've ever seen on fark.

Thanks. There's a bit of an art to trying to explain things to the layman without sounding like a complete blowhard in the process. Glad it worked; at least this time.

Flt209er:

I'd give you a high five but by the time they figure out how to do that we'll all be punching each other in the face via tubes over on the politics tab

/I had to google some basic probability functions today
//and it made me sad how much I'd forgot