The capacitor reacts very differently at the two different frequencies, and in exactly the opposite way an inductor reacts. 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. In this case, the current is proportional to the slope of a sine wave. In fact, the slope of a sine wave is a cosine wave as shown in Fig.
Now substituting the sine wave expression for voltage into the current equation. We obtain. From equation 2 one finds maximum current to be;. Remembering that the effective values are related to the maximum values by the same ratio, so we can write. The pure capacitance cannot dissipate any power. Rather, capacitance stores or releases energy in the form of the electric field. The capacitive reactive power equals the product V C I C.
Combined Resistance and Reactance. In practice, most circuits contain a mix of resistive components along with reactive components that could be inductive or capacitive. In order to analyze these types of circuits, the use of impedance proves to be an especially helpful tool. As stated before, the impedance of a circuit, regardless of the nature of the components, can be described by the relationship.
Figure 8: Impedance Diagram. In a circuit that contains both resistive and reactive elements, the impedance in the complex plane can be described by the general relationship depicted in Figure 8 , where, in the rectangular form,.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. What do we mean by Inductive and Capacitive Reactance?
Ask Question. Asked 4 years, 5 months ago. Active 4 years, 5 months ago. Viewed times. Improve this question. Add a comment. Active Oldest Votes.
Improve this answer. JBrouwer JBrouwer 1 1 silver badge 10 10 bronze badges. I will update my answer. Every signal can be treated in terms of a linear combination of pure sinusoids, and the total result built up from the results on those simple problems but a reader who needs the answer you have written won't know that right off.
Perhaps just change to "All sinusoidal input signals Which I think is a good match for the overall level of the post a nice job, BTW. If the reactance is greater, then the current will be smaller for the same applied voltage. Reactance being almost similar to electric resistance also differs from it in a few ways. When an alternating current is made to pass through the electric circuit or element, both the phase as well as the amplitude of current will change. Also, the energy is stored in the element containing reactance.
The energy is thus released either in the form of an electric field or magnetic field. The reactance in the magnetic field resists change in the current whereas, in the electric field, the reactance will resist the change in voltage. If the reactance releases energy in the form of a magnetic field, it is called inductive reactance whereas if the reactance releases energy in the form of an electric field, it is called capacitive reactance.
With the increase in frequency, capacitive reactance is decreased, and inductive reactance is increased. An ideal resistor will have zero reactance, whereas ideal inductors and capacitors will have zero resistance. The inductive reactance is the reactance that is produced due to the inductive element inductor.
0コメント