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Alternating Voltage Applied to a Condenser

Author: E.E. Kimberly

A sinusoidal voltage applied to the terminals of a condenser produces a sinusoidal current. When the applied voltage is maximum, the voltage of the charge on the condenser is equal to it and opposite in sign, and therefore no current flows. Experiment shows that, as the applied voltage decreases, the potential of the charged condenser forces current out of the condenser, and that this current is maximum at the instant at which the applied sinusoidal voltage is zero. The current taken by a perfect condenser leads the applied voltage by 90° and is, therefore, a function of rate of change of voltage, or


It is not possible to make a perfect condenser, but for all except the most exacting cases the angle may be taken as 90°.

Last Update: 2010-10-05