Recent content by enroger

Yes, that's it. This is just like an ordinary solenoid. What I don't understand is what determines you have far field or near field emission? I mean with the plane wave solution B = E/c, and that any solution would be a superposition of plane wave solution, then there should be no near...

In low freq magnetic communication, the carrier is not EM wave but low frequency varying magnetic field. Most of the energy is transmitted within the mag field, very little result in EM wave. I find this very strange, because in Maxwell equation's plane wave solution, B is always equal to E/c...

Thanks for helping me out guys! I'm in good shape to pick up a book now :)

The capacitors are there to soak in the current so as to allow shorter antenna right? Can the antenna be viewed as a capacitor element in the circuit or antenna has an inductor element too? So by having an external LC circuit you can tune the whole thing to minimize impedance.

Now I see, thanks for the explanation! Charge carriers move a lot slower than c, but E field does, now it makes a lot of sense.

Thanks for the reply. So it's about efficiency. But what determines the efficiency at different frequency? Specifically at a certain frequency what determines how much input energy got coupled into EM wave and how much got "wasted"? Why is it antenna length dependent? If this is too much math...

In making antennas, the higher the frequency the smaller the length of the antenna. The length of the antenna is somewhat equal to the wavelength. But why? I mean, can't we just grab any piece of metal and put in AC current and there would be EM wave correspond to the AC signal whatever the...

The other day I was working in the lab and observed a very interesting fluid dynamic thing in a beaker: I was cooking acetone on a hot plate to clean a sample, then I see little bubbles on the surface bouncing around. The strange thing is that those bubbles act EXACTLY like a ball on a...

The fact that there is a pulse of E field accompany with B field when the solenoid got turn on has no problem. What I want to know is: When there is no change in current a long time after turn on, therefore no change in B field around the wire, would there still be a E field around the wire? I...

Consider a wire, if I suddenly pass current on it. There would be an instant localized B field around the wire. Since there is sudden change of B field, there will also be a finite E field. According to Maxwell equation E=B/c. As the B field spread out the E field will follow, even when the...

I don't think this kind of momentum can be compared to the momentum of photons, since the force is actually lorenz force here which can be many magnitude larger than photon's force depends of field strength and current. Also, the distance can be 3 meter with magnetic fields of the two...

Say we have two electromagnet A and B a light year apart from each other. Someone turn on A and a magnetic field is created and propagate at c toward B. It takes a year for the mag field from A to arrive B, B is turned on just before A's field arrive. B's field made to be opposite from A and...