How does capacitive reactance vary with frequency

At the higher frequency, its reactance is small and the current is large. Capacitors favor change, whereas inductors oppose change.

Capacitors impede low frequencies the most, since low frequency allows them time to become charged and stop the current. Capacitors can be used to filter out low frequencies. For example, a capacitor in series with a sound reproduction system rids it of the 60 Hz hum. Although a capacitor is basically an open circuit, there is an rms current in a circuit with an AC voltage applied to a capacitor.

This is because the voltage is continually reversing, charging and discharging the capacitor. If the frequency goes to zero DC , X C tends to infinity, and the current is zero once the capacitor is charged. Capacitors have the opposite effect on AC circuits that inductors have. Just as a reminder, consider Figure 3, which shows an AC voltage applied to a resistor and a graph of voltage and current versus time.

The voltage and current are exactly in phase in a resistor. There is no frequency dependence to the behavior of plain resistance in a circuit:. Figure 3. Inductive reactance X L has units of ohms and is greatest at high frequencies. X C has units of ohms and is greatest at low frequencies. Conceptual Questions 1. Presbycusis is a hearing loss due to age that progressively affects higher frequencies. A hearing aid amplifier is designed to amplify all frequencies equally.

Would you use a large inductance or a large capacitance in series with a system to filter out low frequencies, such as the Hz hum in a sound system?

High-frequency noise in AC power can damage computers. Does the plug-in unit designed to prevent this damage use a large inductance or a large capacitance in series with the computer to filter out such high frequencies? Explain why the capacitor in Figure 4 a acts as a low-frequency filter between the two circuits, whereas that in Figure 4 b acts as a high-frequency filter.

Figure 4. Capacitors and inductors. Capacitor with high frequency and low frequency. If the capacitors in Figure 4 are replaced by inductors, which acts as a low-frequency filter and which as a high-frequency filter?

What value of inductance should be used if a What capacitance should be used to produce a 2. What is the inductance? What is the capacitance? What minimum inductance should it have to produce a 2. The capacitor in Figure 4 a is designed to filter low-frequency signals, impeding their transmission between circuits. Resistance is negligible. Updated On: Share This Video Whatsapp. Text Solution. Solution :. Very Important Questions. National Education Day: e-learning Transforming Educational Landscape National education day: e-learning transforming educational landscape.

By using this site you agree to the use of cookies. Check our Cookie Policy for more details. I feel, capacitor has infinite resistance , since charge generally does not flow through a capacitor , it stores the charge. So a capacitor allows no current to flow "through" it for DC voltage i. The voltage across the plates of a capacitor must also change in a continuous manner, so capacitors have the effect of "holding up" a voltage once they are charged to it, until that voltage can be discharged through a resistance.

A voltage was applied across the inductor. This causes current to flow through it. So the current flowing through the inductor and the magnetic field established due to the current interact with each other to induce an EMF in the inductor, which opposes the applied voltage effect opposes cause according to Lenz's law. When capacitors or inductors are involved in an AC circuit, the current and voltage do not peak at the same time. This leads to a positive phase for inductive circuits since current lags the voltage in an inductive circuit.

The phase is negative for a capacitive circuit since the current leads the voltage. Capacitive reactance symbol XC is a measure of a capacitor's opposition to AC alternating current. Like resistance it is measured in ohms, but reactance is more complex than resistance because its value depends on the frequency f of the signal passing through the capacitor. Write Your Answer. Similar Asks What is the unit of frequency? What can be used to measure frequency? How do you measure the frequency of light?

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