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# E.M. Theory....

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#### Rohit Chatterjee

##### New Member
Why is it that only accelerated charge produces EM field....Any moving charge will create an E field and a H field...so why not an EM field???
Plus,does an electron feel the force exerted by its own E field???

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What do you mean by EM field? Do you mean Electro-Magnetic wave? If so, electrons have to vibrate back and forth to make waves. Vibration as such required the electrons to accelerate.

Yes, you can not have a static EM field, they consist of waves that are continually changing. To make a EM wave the electrons have to be accelerating, as in an AC circuit where they vibrate back and forth.

But interestingly, you can make an EM wave by rotating the electrons in a circle at a constant speed, as was done in the old cyclotrons. A magnetic field directed the electrons into a circular orbit. The magnetic field force on the electrons to do this appears as acceleration to the electrons and generates EM radiation (naturally called cyclotron radiation).

EM Field

Are you saying a Magnetic field produced by DC Voltage in a coil is not an EM field and static?

A magnetic field is not an EM field. I've never heard of any such thing as a static EM field, and I studied field theory in college. Of course, an E field and a magnetic field can exist at the same place is space. That doesn't make it an EM field though.

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And what about the electron....does it experience the force exerted by its own E filed????
Even if it did the net force would be zero coz the vector sum of the force would be zero....but what if the E field produced has different magnitudes along different directions???

And what about the electron....does it experience the force exerted by its own E filed????
Even if it did the net force would be zero coz the vector sum of the force would be zero....but what if the E field produced has different magnitudes along different directions???
Certainly the electron will experience force from it's own E field if it encounters another E field, such as from another eletron. That's what keeps electrons separated in a conductor since E fields of the same polarity repel.

Don't really understand your question about E fields with different magnitudes. What's causing the different magnitudes?

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Well actually i came across this article about the E field created by an accelerated electron...it said that apart from the static Coulomb field,an accelerated electron creates a dynamic E field...now this dynamic field has different magnitudes along different directions,and opposes the motion of the electron....
Now this is very similar to the case of currents and inductors and so quite possible...its just that i had never come across any article previously which claimed an electron experiences the force exerted by its OWN E field....n so want ur views

An accelerating electron does indeed experience a force from the dynamic EM field. That's how the energy from an AC current in a wire (antenna) is transferred to the EM radiated field and carried into space as a radio wave.

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