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The X-shaped dipoles give it a wide bandwidth to cover both the VHF (174–216 MHz) and UHF (470–700 MHz) TV bands. It has a gain of 5 dB VHF and 12 dB UHF and an 18 dB front-to-back ratio. Large planar array antenna of a VHF Russian mobile air defense radar, the Nebo-M. It consists of 175 folded dipole antennas.
The monopole antenna is essentially one half of the half-wave dipole, a single 1 / 4 wavelength element with the other side connected to ground or an equivalent ground plane (or counterpoise). Monopoles, which are one-half the size of a dipole, are common for long-wavelength radio signals where a dipole would be impractically large.
A dipole is characterised by its dipole moment, a vector quantity shown in the figure as the blue arrow labeled M. It is the relationship between the electric field and the dipole moment that gives rise to the behaviour of the dielectric. (Note that the dipole moment points in the same direction as the electric field in the figure.
The theory of special relativity plays an important role in the modern theory of classical electromagnetism.It gives formulas for how electromagnetic objects, in particular the electric and magnetic fields, are altered under a Lorentz transformation from one inertial frame of reference to another.
Eddy currents are minimized in these devices by selecting magnetic core materials that have low electrical conductivity (e.g., ferrites or iron powder mixed with resin) or by using thin sheets of magnetic material, known as laminations. Electrons cannot cross the insulating gap between the laminations and so are unable to circulate on wide arcs.
The problem with matrix circuits is that, when several notes are pressed at once, the current can flow backward through the circuit and trigger "phantom keys" that cause "ghost" notes to play. To avoid triggering unwanted notes, most keyboard matrix circuits have diodes soldered with the switch under each key of the musical keyboard .
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism.
A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. [16] He also explained the apparently paradoxical behavior [17] of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. [14]