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. Construct Your Own Problem Consider the use of an inductor in series with a computer operating on 60 Hz electricity.
Construct a problem in which you calculate the relative reduction in voltage of incoming high frequency noise compared to 60 Hz voltage. Among the things to consider are the acceptable series reactance of the inductor for 60 Hz power and the likely frequencies of noise coming through the power lines. Skip to main content. Search for:. Reactance, Inductive and Capacitive Learning Objectives By the end of this section, you will be able to: Sketch voltage and current versus time in simple inductive, capacitive, and resistive circuits.
Calculate inductive and capacitive reactance. Inductors and Inductive Reactance. Example 1. Calculating Inductive Reactance and then Current a Calculate the inductive reactance of a 3. Discussion The inductor reacts very differently at the two different frequencies.
Capacitors and Capacitive Reactance. Example 2. Calculating Capacitive Reactance and then Current a Calculate the capacitive reactance of a 5. Discussion The capacitor reacts very differently at the two different frequencies, and in exactly the opposite way an inductor reacts. Does inductance depend on current, frequency, or both?
What about inductive reactance? Learn more. What does "current leads voltage" mean? Ask Question. Asked 1 year, 10 months ago. Active 1 year, 10 months ago. Viewed 2k times. I am not well-versed in electronics. What does it mean for current to lead voltage? Sabuncu Sabuncu 5 5 silver badges 15 15 bronze badges. It's talking about complex stuff like frequency response, when you don't understand the basics.
You need a different book. The classic undergraduate textbook is The art of electronics by Horowitz and Hill, which is very good. If you need to start a bit further back though, I'd suggest looking up an AS-level textbook, which is probably a better kicking-off point.
Show 7 more comments. Active Oldest Votes. Jasen Jasen That is, why is this a thing? Thank you. Add a comment. Andrew Morton 1, 1 1 gold badge 13 13 silver badges 23 23 bronze badges. For capacitors C the I leads the E. RoyC RoyC 7, 6 6 gold badges 22 22 silver badges 38 38 bronze badges. Sign up or log in Sign up using Google.
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