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Frank
If I have two parallel plates seperated by an air space and the plates are connect to a batttery I have a capacitor with an E field between the plates and squeezing out the sides. In steady state there's no current flow so I have no H field. If I have a coil or a solenoid and connect it to a battery I have a current flow with a strong H field but I'm not certainabout the E field. Can this be taken to the next step to answer my original question? tnx -- 73 Hank WD5JFR "Frank" wrote in message news:4Pyie.68625$tg1.4151@edtnps84... "Henry Kolesnik" wrote in message ... As I understand it a shielded loop (non-magnetic shield) favors the magnetic field. Correct. If I wanted to measure the difference between the 2 fields how would I measure the electric field? Any antennna can measure the electric field, you simply have to know the antenna factor. Antenna factors can be calculated for various structures; for example the aperture of a half wave dipole is given by: 0.13*lambda^2. Simple calculations can then provide the antenna factor, and relate the E field (in V/m) to the received signal. The electric and magnetic fields are related by a constant -- the impedance of free space, 377 ohms. i.e. E/H = 377. In the vicinty of an antenna (the near field) the impedance of free space becomes a complex number. A loop shielded with magnetic material would probably reject both fields. Probably true, but have never experimented with such antennas. The 3.5 foot loop for my old HP comparator for WWVB is totally non-magnetic. Can I generate and transmit each field separately? If so how would I do it? No. The E field cannot exist without the H field. See the relationship above. Some people claim to have invented antennas that seperately generate E and H fields. Such antennas are known as "EH" and "Crossed-field", and have largely been rejected by the engineering comunity as bogus. The designers claim that they do not conform to Maxwell's Equations, but some other indefinable mathematics. Regards, Frank tnx -- 73 Hank WD5JFR |
#2
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Henry Kolesnik wrote:
"If I have a coil or solenoid and connect it to a battery I have a current flow with a strong H field but I`m not certain about the E field." Resistance somewhere is limiting the current. The E field accompanies the resistive voltage drop. Static fields don`t make waves. Only the rate of change makes a disturbance which propagates in waves, E&M, which generate each other. Best regards, Richard Harrison, KB5WZI |
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