Electrical Engineering ⇒ Topic : Beam Deflection
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Lalan
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Beam Deflection The electrons emerge from the lens to converge at the screen into a spot. Before this, they pass through a deflection region in which they enter with an initial velocity yo. Therefore, the beam of electrons is deflected first by a set of horizontal plates to sweep the beam vertically and a second set of vertical plates to sweep the beam horizontally. This type of deflection is by coils which deflect the beam by magnetic fields produced by current. The signal whose image is to be observed and measured is fed to the horizontal or Y plates. The potential of the signal exerts a force on the electron given by F = eE and this force being perpendicular, deflects the electron to the positive plate and accelerates it at the same time. The path of the electron between the plates becomes parabolic. After the beam emerges from the Y plates, it is moved sideways across the screen along the X-axis by the vertical plates or X plates.To the X plates, may be fed another signal as in the case of modulation or time base waveform as a saw tooth in which the X-axis becomes a time domain in t. | |
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