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# What is the Relationship beteen Capacitance and frequency?

Updated: 8/11/2023

Wiki User

11y ago

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.

Wiki User

14y ago

Wiki User

14y ago

A major use is for timing. When you have a capacitor and a resistor, you have an RC circuit, which has a time constant associated with it based on the values of the cap and resistor.

(V final) = (V initial)*e^(-t/RC) where t = time.

Wiki User

13y ago

A: As frequency increases the capacitor internal inductance will eliminate some of the desired capacitance. A very hi speed PWM will have expenses capacitors with four leads to eliminate some of the internal inductance

Wiki User

9y ago

In a dc circuit a capacitor acts like a battery, storing charge and releasing it whenever the dc load demands more charge than the dc voltage source can give.

Capacitors are used to give a steady dc output from an unregulated ac rectifier: whilst the voltage increasesthe the capacitor gets charged to the peak of the voltage applied. As the rectified ac voltage then reduces towards zero, the capacitor discharges and hence helps give a more steady dc output from the rectifier.

Wiki User

11y ago

Changing the capacitance of a capacitor has no effect on the frequency of an AC

applied across it. Likewise, changing the frequency of an AC applied to a capacitor

has no effect on the value of the capacitor. In that sense, there is no relationship

between capacitance and frequency.

But . . .

If the capacitor happens to be one of the frequency-determining elements in the

circuit where the AC is being produced, only then, increasing the capacitance

generally decreases the frequency of the AC signal being produced.

Wiki User

15y ago

Simple relationship: Capacitance is *defined* to be the ratio of charge to voltage: C=Q/V

Wiki User

14y ago

Capacitive reactance is inversely proportional to frequency.

Wiki User

12y ago

go and refer books .that wiil provide enough information.books are better than this...................................by murugapandi subbiah (EEE)

Wiki User

13y ago

Capacitive reactance is a term that is applicable to AC, not DC.