Field Versus Charge Velocity
Date: Spring 2013
When generating and transmitting electricity, why is it that the electromagnetic fields move so much faster than the related electrons?
The electromagnetic fields are not attached to the electrons. They are continuously emitted by the electrons, kind of like a bucket of water leaking out water. The speed at which the water moves is not determined by the speed of the bucket. If traveling along dirt, the water will not move once leaked. If traveling along a tilted plastic surface, the water will run downhill rather quickly. The water will not even travel in the same direction as the bucket. Properties of the electron allow us to calculate what the electric field will be like, but they do not control the field once it has left the electron. Once emitted, the field is a form of light (radio, microwave, infrared, visible, ultraviolet, etc.).
Dr. Ken Mellendorf
Illinois Central College
The charged particles creating the fields have mass, and the fields do not. Particles having mass cannot travel as fast or faster than the speed of light, according to Einstein's theory of Special Relativity. The fields, in some sense, are light, and by definition travel at the speed of light. If you set up an oscillating charged particle, you can create an oscillating electric and magnetic field which propagates away at the speed of light. It doesn't really matter if the charges are moving slowly; the fields they set up travel away at the speed of light.
Kyle J. Bunch, PhD, PE
Thanks for the question. The electromagnetic field moves at the speed of light as the mass of the photons that compose the field is zero. Since the electrons have mass, they move slower than the electromagnetic field.
I hope this helps. Please let me know if you have more questions.
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Update: November 2011