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rodin
2010-Mar-07, 06:55 PM
Moving electrons in a wire generates a magnetic field. The drift current is typically quite slow yet the field strong, with electromagnets being a good illustration of this, used for example to lift scrapped cars in a crushing plant.

Ccurrent is possible because the outer shell electrons in a metal are delocalised. In essence a metal is a sea of negative electrons flowing around a lattice of positively charged metal ions.

If I take the same wire and apply motion to it at equivalent speed of the drift current and in the same direction, I create an identical flow of electrons through space. However no magnetic field is generated.

Why is this? Is it because the equivalent positive charge of the fixed metal 'ions' creates an equal and opposite magnetic field?

korjik
2010-Mar-07, 07:39 PM
Moving charges create a current. Current creates a magnetic field. A field that is dependent on the sign of the charge.

So, yeah, you are moving a like number of positive and negative charges and cancelling out any fields.