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The short answer to the question is the capacitive reactance of a capacitor in a DC circuit is infinite.

In a DC circuit, disregarding transient behavior and any leakage effects, a capacitor is effectively an open circuit, and so its reactance is essentially infinite.

Capacitive reactance is calculated as Xc =1/(jwC) where w is the angular frequency in radians per second, w = 2*pi*f, C is in Farads, and f is in Hertz.

With DC, both f and w are zero, and, theoretically, the formula,

Xc =1/(jwC) = limw-->0 [1/(jwC)] becomes infinitely large. In any practical circuit, however, there is always some leakage, so the impedance of the a capacitor will be quite large, on the order of megohms, but still finite.

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