Understanding Relative Electricity: An Electron's Perspective

[sci-guy]

I just read the following innocent sounding statement, which got me thinking:

"An electron in motion relative to an observer generates a magnetic field..."

This implies that, for an observer moving alongside at the same speed as the electron, there is no magnetic field. I understand the basic concept of relativistic motion, but I'd be interested in comments explaining what's going on here. I'm no scientist, but as I understand it, an electron in motion essentially implies an electric current. So there's no current and no field for our observer. Since energy is never created or destroyed, in what form is it here?

We could reframe the statement and say simply that, from its own perspective, the traveling electron generates neither a current, nor charge, nor magnetic field (since, relative to itself, it is never in motion). In fact, from the electron's perspective, the entire universe is spinning in a "positive" direction around it.

Wow.

 

[ghwellsjr]

See this thread for an extensive discussion on this topic:

https://www.physicsforums.com/showthread.php?t=465297

 

[Naty1]

Well you may consider yourself "no scientist" but be careful, you post implies you already know more than 98% of the population!...

Different observers "see" (measure) different things...

As a simple example, two distant observers may time the occurrence of a distant light flash differently and two observers in relative motion will likely hear a different pitch as a train passes.

See this diagram to get an idea of what an electromagnetic wave looks like:
http://en.wikipedia.org/wiki/Electromagnetic_wave#Properties

...the traveling electron generates neither a current, nor charge, nor magnetic field (since, relative to itself, it is never in motion

Everything IS relative...but in it's own frame charge is retains it's value ...but you measure no current nor a magnetic field...and time, for example, is also a constant...
BUT
if you and I (say we are each an electron if you like) pass each other at high speed, we each see the other's clock as slower than our own...which is "right"...both are...and we also observe the OTHER has a magnetic field...weird, I know...

 

[sci-guy]

Thanks for both posts; that clarified things. Maybe my question doesn't apply -- you say (and I also read in one of the other refs) that the electron retains its charge even if I'm speeding alongside it. So no energy is lost in the equation, which was my original question.

So there is no energy in a magnetic field? (Told you I'm no scientist.) If there is, we still have conflicting energy readings by our two observers (one sees the field, one doesn't), and would have to account for the discrepancy. Where is the energy for the speeding observer who doesn't see the field? The obvious answer seems that its in his own speeding velocity. I suppose QM has equations to convert a magnetic field into velocity.

Did I answer my own question?

 

[JesseM]

There's a good discussion on the following page about how electric and magnetic forces from the same collection of charges look different depending on what frame you use, and indeed if you pick the right frame the magnetic force may disappear entirely, but all frames make the same predictions about physical results like which direction a charged particle is deflected:http://physics.weber.edu/schroeder/mrr/MRRtalk.html