How does current enter in an Antenna?
400251
the signal applied to the antenna is in relation to groud. the signal spewed out by radio stations travels thru the air. and a very small signal is placed on the antenna in relation to the ground. the receiver circuit takes over from there. if you drive by a radio station you will see their big antenna very isolated from ground. to prevent arching. the signal coming from them is very powerful. \n\n                                  Greg..
173670
V=It/C\n\nwhere\nI is current in amps\nV is voltage in volts\nt is time constant in seconds\n\nIn an ideal capacitor, this holds true.  Theoretically, an ideal capacitor has no leakage current and no inductance.
932826
The radio uses a transducer called an aerial to convert the radiowaves to current in a conductor, after low noise amplification and filtering to reject most of the other radiowaves that the transducer has converted, the short-term changes in the current are interpreted as a wanted modulation of the radiowave.
274304
Here's a good source of info:\nhttp://ece-www.colorado.edu/~kuester/Coax/connchart.htm
70878
Ohm's Law (named after Georg Ohm, a German physicist) states that the electric current I flowing through a given conducting material (conductor means current can flow through it) is equal to the applied voltage V divided by the resistance R:  I=V/R. Ohm's Law deals with the relationship between voltage and current in an ideal conductor.  The resistance R is sometimes called a "lumped element abstraction."\n\nFor general application to alternating-current circuits where inductances and capacitances as well as resistances may be present, the law must be amended to I=V/Z, where Z is impedance.\n\nOhm's Law is a macro-level, aggregate rule as to how current, voltage, and resistance are related.  But it is not a true "law" of nature in that it really is an approximation of behavior that holds true in most circumstances.\n\nOhm's Law may not hold due to:  1) the kind of conducting material the current is flowing through (some conductors do not follow Ohm's Law)  2) how much voltage is applied to the conducting material; as voltage is increased or decreased to extremes, then the linear Ohm's Law relationship breaks down   3) how small the wavelength of a periodically time-varying voltage applied to the conductor is with respect to the conducting circuit\n\nThe deeper reasons behind why Ohm's Law does describe macro behavior in "ohmic" conducting materials requires diving into a little bit of solid state physics and understanding Maxwell's equations.
147664
It's not clear from your question, are you trying to design an antenna?  What is the purpose of this experiment?\n\nIf you want to build an antenna, I would suggest a magnetic dipole.  This is the old fashion UHF type attenna (the loop).
211231
It depends on both the type of current and the circuit.  For example, AC and DC currents passing through a circuit with reactive elements (capacitors and inductors) will much diffreently from one another.... Ohm's law always applies however...
1060081
First of all, it's an engineering (specifically, electronics/telecoms) question, not physics.\nSecondly, AFC is a unit usually integrated to L.O. (local oscillator) in order to compensate frequency deviations caused by noise (thermal) or circuit instabilities (e.g. power supply variations). This module mainly consists of a frequency-to-voltage or frequency-to-current converter which feeds back negatively a sample of output to input control. A famous example is in TV tuners, where the selective frequency of a broadcasting channel is to be adjusted by a VCO (Voltage Controlled Oscillator). Here the AFC module may consist simply of an integrator (a resistor and capacitor) which samples the output and feeds it back to input via a differentiator (like Op-Amp).\n\nIn radars, however, due to their more accuracy, AFC is very complicated. In fact, it is a completely active module with a self-compensate thermal circuitry. Also since the frequency of radars are generally in microwave range, the circuits totally differ from what you may find in general telecoms circuits.
232108
Ideally a capacitor has an infinite resistance (which is a DC measurement). However the AC equivalent of resistance, reactance (usually denoted as X), tells you how much AC current a capacitance passes with a given AC voltage applied across its terminals. Reactance depends on the AC frequency. It is X = 1/(C*W), where C is capacitance and W (omega) is 2*pi*frequency. Similarly to Ohm's law, you can find average current from E = I*X. Unlike Ohm's law, this is true for average current but not for instantaneous current, since E and I are 90 degrees out of phase.
1015158
initailly it was believed that current flows from+ve to -ve. but actually its electrons moving from -ve to +ve. so it became - current flows from +ve to -ve (thoritically) electrons from -ve to +ve (actually)\n\nhope that answeres
619191
It would definitely effect the field and the result would  be vector addition. If the source (here current) is supposed to generate a constant electric field then current gets effected but if there is no constraint then there is no reason for current to change.
126863
The RF waves emanating from an antenna are generated by the movement of electrical charges in the antenna. Electromagnetic waves can be characterized by a wavelength and a frequency. The wavelength is the distance covered by one complete cycle of the electromagnetic wave, while the frequency is the number of electromagnetic waves passing a given point in one second. The frequency of an RF signal is usually expressed in terms of a unit called the "hertz" (abbreviated "Hz"). One Hz equals one cycle per second. One megahertz ("MHz") equals one million cycles per second.
110616
Every station has a transmitter that radiates radio signals around its area. A lot of the signals reflect off the atmosphere, and this along with the power of the transmitter determines how much area the signal covers.\n\nHow the transmitter sends out a radio signal?\n\nThere's an excellent in-depth discussion on Wikipedia (the link I provide), but I copy here the one important point:\n\n"In principle any conductor (wire) carrying an alternating current will radiate a radio signal. Thus a basic transmitter is just an oscillator connected directly to a wire antenna."\n\nSo you need a conductor with an alternating current going through it. This will send out radio waves. Of course, its more complex if you want the radio signal to contain a voice or song broadcast of course.\n\nRemember that a radio wave is just another type of electromagnetic radiation, along with xrays, and light. The only thing that seperates light and radio is the wavelength (def: every oscillating electromagnetic signal has a property that specifies the distance from one peak of the signal to the next) of the radiation. \n\nOur eyes are basically receivers that can interpret electromagnetic radiation within a certain range. So think of radios as a type of artificial eye that reacts to radio signals, and that a radio station is basically one huge flashlight.\n\nThat's as simple an analogy I can make.
524846
B'coz wavelength decides the power gain that transmitting antenna should have .\n& distance that can be covered by signal also depends on wavelength.
119408
there where a time when engineers/scientist thought of a conventional current flow in which the current flows from the postive to the negative. that time diodes are in existence. through times, they found out that current really flows in opposite directions, that is from negative side to positive side that is the electron flows. and since diodes are in existence they just make a vertical lines in an arrow to represent that the current flows in the other side...
470161
The above answer is wrong, that equation is for the force on the wire!\n\nFor the magnitude of the induced EMF, you need to use BLV.\nThen Use V=IR to get the current.\n\nThe directions are a bit more tricky - you have to use the Left hand rule or the corkscrew rule to do this bit.\nJust remember than to obey Lenz's Law, the current must flow in such a way that the force on the wire given by BIL must oppose the direction of motion of the wire.\n\nSo, to put it simply, the curent has to be up in the diagram you drew above.\n\nBy the way, in order for current to flow, you must consider that this wire is part of a complete circuit.
114930
I'm assuming that the current is not changing with time other than the initial turn-on transient.\n\nWhen the current has reached a steady state (didn't say reached zero, but some final state), you are in the area of electromagnetics called electro/magnetostatics and the magnetic and electric fields are uncoupled. For the situation that you describe (I'm assuming no stationary charges external to the wire), the Electric Field Density is zero.\n\nYou might be tempted to use Gauss' Law to find the Electric Field from an individual electron as it moved down the wire, but the summation at any particular point in space from all charges moving in the wire will sum to zero.\n\nWhen the current is first turned on you will have a changing magnetic field and therefore an electric field. However, that electric field will die away rapidly.