LYCOS RETRIEVER 
Capacitor: Voltages
built 631 days ago
The capacitor has a reactance of 7.9k at 20Hz, and 22k at 7.2Hz (this is the -3dB frequency). At this frequency, if 1V is applied to the input, 707mV will be 'lost' across the cap, and the amplifier will get an input signal of 707mV. The reason for the voltages not being 50% of the input voltage is due to phase. This is quite normal, and causes no problems. A double blind test of any two capacitors of the same value and reasonable construction will not reveal any audible difference - even if the music has significant very low frequency content, and the loudspeakers can reproduce it. At 40Hz, the capacitor has a reactance of just under 4k, and at 1kHz this has fallen to 159 ohms. These figures apply reasonably accurately at all voltages, impedances and frequencies.
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The basis of a dynamic RAM cell is a capacitor. They are ... used for power-supply smoothing (or "decoupling"). This is especially important in digital circuits where a digital device switching between states causes a sudden demand for current. Without sufficient local power supply decoupling, this current "spike" cannot be supplied directly from the power supply due to the inductance of the connectors and so will cause a sharp drop in the power supply voltage near the switching device. This can cause other devices to malfunction resulting in hard to trace glitches.
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Some DMMs have modes for capacitor testing. These work fairly well to determine approximate uF rating. However, for most applications, they do not test at anywhere near the normal working voltage or test for leakage. However, a VOM or DMM without capacitance ranges can make certain types of tests. For small caps (like .01 uf or less), about all you can really test is for shorts or leakage. (However, on an analog multimeter on the high ohms scale you may see a momentary deflection when you touch the probes to the capacitor or reverse them.
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Utility capacitor bank switching can have negative impacts on power quality, especially for customer power systems. AC and dc drives, along with other electronic equipment, can be very sensitive to transient voltages. Utility capacitor bank switching transients can be magnified at low voltage capacitor locations on customer power systems, causing drives to trip and production and other processes to stop. In a time when customers are being allowed to choose their power provider, utilities cannot afford to be seen as the cause of customer power problems.
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It is such a capacitor which is used for high voltage DC & AC on medium loss and medium accuracy of capacitance stability. It is made by wrapping thin layer of aluminium with the layers of tissue paper and to remove the moisture from paper, thin layer of wax is used on it. In the matellised paper capacitor, metal film is used in place of aluminium for electrodes. The value of paper capacitor is generally in between 0.001 micro farad to 0.2 micro farad. Their voltage capacity is maximum upto 100V. Now a days, polyester plastic film is used on the tissue paper in the paper capacitors. Due to the use of this film, its dielectric constant raises as a result it does not damages on the high voltage.
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Since the voltage across a capacitor is proportional to the integral of the current, as shown above, with sine waves in AC or signal circuits this results in a phase difference of 90 degrees, the current leading the voltage phase angle. It can be shown that the AC voltage across the capacitor is in quadrature with the alternating current through the capacitor. That is, the voltage and current are 'out-of-phase' by a quarter cycle. The amplitude of the voltage depends on the amplitude of the current divided by the product of the frequency of the current with the capacitance, C.
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