# The Naked Scientists Forum

### Author Topic: Why do electrons move in a magnetic field?  (Read 4218 times)

#### thedoc

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##### Why do electrons move in a magnetic field?
« on: 11/08/2013 13:30:02 »
Don Kingsley  asked the Naked Scientists:

WHY does moving a conductor relative to a magnetic field promote a flow of electrons?

What do you think?
« Last Edit: 11/08/2013 13:30:02 by _system »

#### Pmb

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##### Re: Why do electrons move in a magnetic field?
« Reply #1 on: 13/08/2013 03:24:49 »
Don Kingsley  asked the Naked Scientists:

WHY does moving a conductor relative to a magnetic field promote a flow of electrons?

What do you think?
One of the laws of electromagntism is the Lorentz force law which states

F = q(E + vxB)

which means that when only a magnetic field is present and a charged particle is moving in a magnetic field then there is a force exerted on it which is perpendicular to both the velocity and the magnetic field. If the electrons are in wire and there is a component of that force parallel to a section of the wire then the electrons will flow along that section with a component of the force parallel to the wire. The force causes a current to be set up in the wire. Electrons accelerate in the wire until they hit another electron and then bounce off. This results in a net drift current in the direction of the force.

#### newcomer

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##### Re: Why do electrons move in a magnetic field?
« Reply #2 on: 17/08/2013 15:40:50 »
Please pick up an elementary textbook on Electricity & Magnetism. In there the chaper on the Lenze's law would make it clear as to why a conductor when moved in a magnetic field produces electrons/current.

#### yor_on

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##### Re: Why do electrons move in a magnetic field?
« Reply #3 on: 18/08/2013 19:19:20 »
Try this one
http://van.physics.illinois.edu/qa/listing.php?id=21425

Easiest to think of it, to me that is, is like it was some weird field that is both locally time dependent as well as observer dependent, that meaning whether you are at rest with what you probe, or not. But I'm still trying to understand what the he* a 'field' is :)

But thinking of it that way makes just another question, and one that is really basic to me.
What is 'motion' in a field? Assume a relativistic speed, you have now shrunk your locally measurable universe in the direction of your 'motion', and so you must have shrunk whatever field, or fields, existing? A field in itself doesn't have a motion as I gather? What have a motion is the charged particles creating and moving in that field, relative yourself observing (frame dependency).

As for asking why those laws exist? Wish I knew, they are experimental facts.

#### The Naked Scientists Forum

##### Re: Why do electrons move in a magnetic field?
« Reply #3 on: 18/08/2013 19:19:20 »