What are the applications of very low frequency electromagnetics?

Most power conversion devices contains coils, such as transformers or inductors. These components use electromagnetism to convert AC main power to low-voltage DC power. The varying magnetic fields generated by these components can cause them to physically vibrate at high frequency, resulting in a high-pitched noise.
https://www.howtogeek.com/200466/why-do-some-ac-adapters-and-power-supplies-make-a-whining-noise/

As the Cobra 1500w inverter is constructed analogous to a high-frequency "switching" power supply, it is not recommended to modify it to exceed original specifications. For any inverter intended for applications exceeding 2000W transient peak, it is highly recommended to use a low-frequency "true-sine" inverter. Your Cobra inverter is designed for low-deman applications, and is insufficient for high-demand applications.

Mainly metal detector is used to find hidden object or treasure. It may be precious metal or non precious metal as like non ferrous in non magnetic things. The operation of metal detectors is based upon the principles of electromagnetic induction. Metal detectors contain one or more inductor coils that are used to interact with metallic elements on the ground. The single-coil detector illustrated below is a simplified version of one used in a real metal detector. Best Waterproof Metal Detectorin 2017 Reviewed By Expert

Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.


Having harmonic disturbance problems?
Thinking about Power Quality?
Having harmonic disturbance problems?
Check out Enerdoor's Harmonic Filter series!
Ex: http://www.enerdoor.com/news/view/thinking-about-power-quality

No. An antenna is a "tuned" device used to radiate or receive electromagnetic signals. Its length and shape is a function of the electromagnetic signal frequencies it is designed to radiate or receive. An antenna is designed to "resonate" at its operating frequency for greatest efficiency. A DVD player is not an antenna. It is not designed to radiaite or receive electromagnetic signals. However, it generates electromagnetic signals by decoding information from a spinning DVD disk. Antennas do not "generate" signals. Antennas only convey signals.

UV (ultraviolet) light is, according to Wikipedia, "electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays"
"It is so-named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. These frequencies are invisible to humans, but visible to a number of insects and birds." (wikipedia)

A "band pass" filter attenuates all frequencies except those in its specified range. A "low pass" filter attenuates frequencies above a specified frequency (permitting only lower frequencies to "pass"). A "high pass" filter attenuates frequencies below a specified frequency (permitting only higher frequencies to "pass").

For example, a "band pass" filter rated for 500MHz-4GHz will effectively eliminate all frequencies below 500MHz and all frequencies above 4GHz. A "low pass" filter rated at 10KHz will effectively eliminate all frequencies that are above 10KHz. A "high pass" filter rated at 70Hz will effectively eliminate all frequencies that are below 70Hz.

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.[1] The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.
The electromagnetic spectrum extends from low frequencies used for modern radio to gamma radiation at the short-wavelength end, covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. The long wavelength limit is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length, although in principle the spectrum is infinite and continuous. Hope this helps.

The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength. The sun, earth, and other bodies radiate electromagnetic energy of varying wavelengths. Electromagnetic energy passes through space at the speed of light in the form of sinusoidal waves. The wavelength is the distance from wavecrest to wavecrest.

Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum, with the range of about 3 Hz to 300 GHz.

Like all electromagnetic waves, radio waves are produced by exited electrons when they return to their normal state. Radio waves can be made to carry information by varying a combination of the amplitude, frequency and phase of the wave within a frequency band.

When electromagnetic radiation impinges upon a conductor, it couples to the conductor, travels along it, and induces an electric current on the surface of that conductor by exciting the electrons of the conducting material. This effect (the skin effect) is used in antennas. Electromagnetic radiation may also cause certain molecules to absorb energy and thus to heat up; this is exploited in microwave ovens. Source(s): wikipedia