<blockquote>
  <p>A fixed magnetic field will induce an electrical current in a conductive object moving through the field.</p>
</blockquote>

<p>No. It will induce an EMF in one direction as described in <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir2.html" rel="nofollow noreferrer">HyperPhysics</a>. It will not induce a current since there is no return path.</p>

<p>This is different from induction braking, where you have a magnet with a non-uniform field moving near a conductor. It is the changing magnetic field at points within the conductor that induces the EMF and causes currents.</p>

<p>Alternatively, we can consider how electromagnetic fields transforn according to Relativity. If an object is moving at constant velocity through a uniform B field then, in its rest frame, it will experience a <a href="https://en.wikipedia.org/wiki/Classical_electromagnetism_and_special_relativity#The_E_and_B_fields" rel="nofollow noreferrer">combination of uniform E and B fields</a> which would not produce a current.  (Any current would have to be due to the spacial rate of change of the field, which would be tiny on the scale of the Earth's field.)</p>

CC BY-SA 4.0
2019-02-07T18:10:40.453Z
2019-08-23T04:27:53.193Z
2019-08-23T04:27:53.193Z
Keith McClary
<p>A fixed magnetic field will induce an electrical current in a conductive object moving through the field.  The strength of the eddy currents will depend on the shape and composition of the conductor and also how fast it is moving.  The electrical current produces ohmic heating in the conductor, and some of the kinetic energy of the moving conductor will be turned to heat. This is how induction brakes work.</p>

<p>I wonder if this principle applies to fast moving conductors like asteroids or satellites that encounter planetary magnetic fields.  Are planetary magnetic fields strong enough to act as induction brakes on moving conductors?  A satellite experiencing induction braking would fall to a lower and lower orbit and eventually out of orbit.  Passing asteroids might have their course deviated more than would be expected just from gravity.</p>

<p>My search turned up only this abstract, which attempted to explain why meteorites are hot via this principle.  </p>

<p><a href="http://adsabs.harvard.edu/full/1946PA.....54..482R" rel="nofollow noreferrer">http://adsabs.harvard.edu/full/1946PA.....54..482R</a></p>

<p><a href="https://i.sstatic.net/0aCFV.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0aCFV.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-02-06T03:22:53.297Z
Low Earth orbit speed is 7.8 km/sec. I have not heard of this type of heating or effects on orbits in the Space Age.
Keith McClary
CC BY-SA 4.0
2019-02-06T05:12:18.477Z
Sort of related: https://en.wikipedia.org/wiki/Electrodynamic_tether
PM 2Ring
CC BY-SA 4.0
2019-02-06T06:32:00.580Z
@PM2Ring You could totally make an answer out of that, it's very much related.
Florin Andrei
CC BY-SA 4.0
2019-02-06T09:30:38.327Z
@Florin Maybe someone else could make a good answer to this question from the info in that Wikipedia article, but not me. ;) Ideally, an answer to this question will have some hard numbers and equations relating to the braking and heating effects.
PM 2Ring
CC BY-SA 4.0
2019-02-06T15:39:48.280Z
@KeithMcClary  we need to amplify the Earth's magnetic field!  :-)
Carl Witthoft
CC BY-SA 4.0
2019-02-06T22:19:45.363Z
@PM2Ring - that is cool as stink and I have never heard of it.  Reactionless drive!  Woo!
Willk
CC BY-SA 4.0
2019-02-06T22:40:23.243Z
It is pretty cool. Imagine how much power you could pull from Jupiter's huge magnetic field! Of course, the downside of orbiting near Jupiter is that its big magnetic field means that its Van Allen belts are severe, so it's not exactly a healthy neighbourhood...
PM 2Ring
CC BY-SA 4.0
2019-08-22T22:56:00.647Z
@PM2Ring The electrodynamic tether depends on a return current through the plasma. I don't think we are assuming this for the asteroid, so there will be no current.
Keith McClary
<asteroids><magnetic-field><satellite>
Do planetary magnetic fields slow the movement of conductive extraplanetary moving objects via induction?
Willk
# Do planetary magnetic fields slow the movement of conductive extraplanetary moving objects via induction?

(Asked by: username_0 on 2019-02-06)

A fixed magnetic field will induce an electrical current in a conductive object moving through the field. The strength of the eddy currents will depend on the shape and composition of the conductor and also how fast it is moving. The electrical current produces ohmic heating in the conductor, and some of the kinetic energy of the moving conductor will be turned to heat. This is how induction brakes work.

I wonder if this principle applies to fast moving conductors like asteroids or satellites that encounter planetary magnetic fields. Are planetary magnetic fields strong enough to act as induction brakes on moving conductors? A satellite experiencing induction braking would fall to a lower and lower orbit and eventually out of orbit. Passing asteroids might have their course deviated more than would be expected just from gravity.

My search turned up only this abstract, which attempted to explain why meteorites are hot via this principle.

<http://adsabs.harvard.edu/full/1946PA.....54..482R>

[![enter image description here](https://i.sstatic.net/0aCFV.png)](https://i.sstatic.net/0aCFV.png)

**Tags:** asteroids, magnetic-field, satellite
> **Comments:**
> **username_1**: Low Earth orbit speed is 7.8 km/sec. I have not heard of this type of heating or effects on orbits in the Space Age.  
> **username_2**: Sort of related: https://en.wikipedia.org/wiki/Electrodynamic_tether  
> **username_3**: @PM2Ring You could totally make an answer out of that, it's very much related.  
> **username_2**: @Florin Maybe someone else could make a good answer to this question from the info in that Wikipedia article, but not me. ;) Ideally, an answer to this question will have some hard numbers and equations relating to the braking and heating effects.  
> **username_4**: @KeithMcClary  we need to amplify the Earth's magnetic field!  :-)  
> **username_0**: @PM2Ring - that is cool as stink and I have never heard of it.  Reactionless drive!  Woo!  
> **username_2**: It is pretty cool. Imagine how much power you could pull from Jupiter's huge magnetic field! Of course, the downside of orbiting near Jupiter is that its big magnetic field means that its Van Allen belts are severe, so it's not exactly a healthy neighbourhood...  
> **username_1**: @PM2Ring The electrodynamic tether depends on a return current through the plasma. I don't think we are assuming this for the asteroid, so there will be no current.  

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## 1 answers

### Answer by username_1 on 2019-02-07. Score: -1

> A fixed magnetic field will induce an electrical current in a conductive object moving through the field.

No. It will induce an EMF in one direction as described in [HyperPhysics](http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir2.html). It will not induce a current since there is no return path.

This is different from induction braking, where you have a magnet with a non-uniform field moving near a conductor. It is the changing magnetic field at points within the conductor that induces the EMF and causes currents.

Alternatively, we can consider how electromagnetic fields transforn according to Relativity. If an object is moving at constant velocity through a uniform B field then, in its rest frame, it will experience a [combination of uniform E and B fields](https://en.wikipedia.org/wiki/Classical_electromagnetism_and_special_relativity#The_E_and_B_fields) which would not produce a current. (Any current would have to be due to the spacial rate of change of the field, which would be tiny on the scale of the Earth's field.)


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