Let's say I have a circuit connected to an antenna which listens for a certain frequency range. The antenna would generate an electric current. For an electromagnetic wave we have two main properties- Frequency (or wavelength) and Intensity.
I would like to know what property of EM corresponds to power (electricity). What I mean by this is that does frequency corresponds to voltage (i.e. higher frequency would generate higher voltage) and intensity corresponds to current(i.e. higher intensity would generate higher current), Or the other way around?
The same question for generating EM waves- More voltage would produce higher frequency and more current would produce more intense EM waves or the other way around?
Or am I thinking about it in a wrong way? I guess a different way to ask it would be -in a circuit for detecting EM waves, How would I measure the frequency and how would I measure intensity of that wave? Or while generating EM waves, how would I control the frequency and how would I control the intensity of the wave?

  • 1
    \$\begingroup\$ I think your mixing apples and oranges here. All action is current driven. All potential is based on voltage, but without current you have no 'action', or work being done, even as EM. \$\endgroup\$ – Sparky256 Jun 25 '16 at 0:46
  • 1
    \$\begingroup\$ This is an extremely broad question, however the way you are thinking about frequency generation is not correct. Higher voltage does not correspond to higher frequency. RF/MW frequencies are generated using resonant structures, i.e., crystals or cavities, or at "lower" RF frequencies, L-C resonators. The voltage and current generated in an RF circuit depend on the system impedance, which for low enough frequencies is frequency independent, so for a given power level the amplitudes of the voltage/current waves can be determined based on the impedance. \$\endgroup\$ – Captainj2001 Jun 25 '16 at 0:48

In an EM wave, there are actually 3 characteristics (actually there's even more, but they aren't as important here): frequency, electric field strength and magnetic field strength. The "electric" and "magnetic" components of the wave is why it's called an EM ("electromagnetic") wave. the E component can be thought of as related to voltage in a transmission line, and the M component related to the current flowing in that transmission line. The E and M components are related by the characteristic impedence of the medium through which they are travelling. (Interestingly, even a vacuum has a characteristic impedence for RF/MW.) Like electricity flowing in a wire, the power in the wave is proportional to the product of the electric and magnetic field strengths.

So, to get back to your question, in an RF wave, frequency does not correspond to voltage, in general. And both the voltage (electric field) and current (magnetic field) have corresponding intensities.

Just to confuse things and (almost) completely change the topic, there is a fundamental physical relationship known as Planck's equation, and is expressed by the equation E = hν. Here, "ν" is the Greek letter "nu" (not the English "vee", even though in this website's font it looks the same), and represents frequency. "h" is known as Planck's constant, and E is energy. So here it seems like the energy is proportional to frequency. But this relation only holds on an atomic scale for a single "photon" of energy, which is a much, much smaller quanta of energy than anything we measure in electric circuits or communications. So although Planck's equation might look like it's related to your question, and may even be the origin of your "frequency corresponds to voltage" statement, the scale of Planck's phenomenon is far too small for consideration in normal RF and MW applications.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.