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Inductive and Capacitive Reactance Flashcards
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Inductive and Capacitive Reactance Flashcards

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Questions and Answers

What effect does an inductor have on a change in current?

An inductor opposes a change in current.

What is the phase relationship between current and voltage in an inductor?

Current lags voltage by 90º (ELI).

What is the term for the opposition an inductor presents to AC?

Inductive reactance.

What is the formula used to compute the value of this opposition?

<p>XL = 2πfL.</p> Signup and view all the answers

What happens to the value of XL as frequency increases?

<p>XL increases.</p> Signup and view all the answers

What happens to the value of XL as inductance decreases?

<p>XL decreases.</p> Signup and view all the answers

What effect does the capacitor have on a changing voltage?

<p>The capacitor opposes any change in voltage.</p> Signup and view all the answers

What is the phase relationship between current and voltage in a capacitor?

<p>Current leads voltage by 90º (ICE).</p> Signup and view all the answers

What is the term for the opposition that a capacitor presents to AC?

<p>Capacitive reactance.</p> Signup and view all the answers

What is the formula used to compute this opposition?

<p>XC = 1 ÷ 2πfC.</p> Signup and view all the answers

What happens to the value of XC as frequency decreases?

<p>XC increases.</p> Signup and view all the answers

What happens to the value of XC as capacitance increases?

<p>XC decreases.</p> Signup and view all the answers

What is the formula for determining total reactance in a series circuit where the values of XC and XL are known?

<p>X = XL - XC or X = XC - XL.</p> Signup and view all the answers

What is the total amount of reactance (X) in a series circuit which contains an XL of 20 ohms and an XC of 50 ohms? (Indicate whether X is capacitive or inductive)

<p>30 Ω (capacitive).</p> Signup and view all the answers

What term is given to total opposition to AC in a circuit?

<p>Impedance.</p> Signup and view all the answers

What formula is used to calculate the amount of this opposition in a series circuit?

<p>Z = √(R² + X²).</p> Signup and view all the answers

What is the value of Z in a series AC circuit where XL = 6 ohms, XC = 3 ohms, and R = 4 ohms?

<p>Z = 5 Ω.</p> Signup and view all the answers

What are the Ohm's law formulas used in an AC circuit to determine voltage and current?

<p>E = IZ and I = E ÷ Z.</p> Signup and view all the answers

What is the true power in an AC circuit?

<p>True power is the power dissipated in the resistance of the circuit or the power actually used in the circuit.</p> Signup and view all the answers

What is the unit of measurement of true power?

<p>Watt.</p> Signup and view all the answers

What is the formula for calculating true power?

<p>True Power = (I²)R.</p> Signup and view all the answers

What is the reactive power in an AC circuit?

<p>Reactive power is the power returned to the source by the reactive components of the circuit.</p> Signup and view all the answers

What is the unit of measurement for reactive power?

<p>var.</p> Signup and view all the answers

What is the formula for computing reactive power?

<p>Reactive Power = (I²)X.</p> Signup and view all the answers

What is apparent power?

<p>The power that appears to the source because of circuit impedance, or the combination of true power and reactive power.</p> Signup and view all the answers

What is the unit of measurement for apparent power?

<p>VA (volt-amperes).</p> Signup and view all the answers

What is the formula for apparent power?

<p>Apparent Power = I²Z or √(True Power² + Reactive Power²).</p> Signup and view all the answers

What is the power factor of a circuit?

<p>PF is a number representing the portion of apparent power actually dissipated in a circuit.</p> Signup and view all the answers

What is a general formula used to calculate the power factor of a circuit?

<p>PF = TP ÷ AP or PF = Cosθ.</p> Signup and view all the answers

An AC circuit has a total reactance of 10 ohms inductive and a total resistance of 20 ohms. The power factor is 0.89. What would be necessary to correct the power factor to unity?

<p>Add 10 ohms of capacitive reactance to the circuit.</p> Signup and view all the answers

What is the difference between calculating impedance in a series AC circuit and in a parallel AC circuit?

<p>In a series circuit, impedance is calculated from the values of resistance and reactance. In a parallel circuit, the values of resistive current and reactive current must be used to calculate total current (impedance current).</p> Signup and view all the answers

An inductor in an AC circuit opposes any change in current flow just as it does in a DC circuit.

<p>True</p> Signup and view all the answers

Current lags the voltage by 90º in an inductor (ELI).

<p>True</p> Signup and view all the answers

The opposition an inductor offers to AC is called capacitive reactance.

<p>False</p> Signup and view all the answers

A capacitor in an AC circuit opposes any change in voltage just as it does in a DC circuit.

<p>True</p> Signup and view all the answers

Current leads the voltage by 90º in a capacitor (ICE).

<p>True</p> Signup and view all the answers

The total reactance of a series AC circuit can be determined by the formula X = XC − XL.

<p>False</p> Signup and view all the answers

Study Notes

Inductive Reactance

  • An inductor opposes changes in current flow.
  • Voltage leads current by 90º in inductors (known as ELI).
  • Opposition to AC from an inductor is termed inductive reactance (XL).
  • The formula for inductive reactance: XL = 2πfL.
  • Inductive reactance increases with rising frequency.
  • Inductive reactance decreases if inductance is reduced.

Capacitive Reactance

  • A capacitor opposes changes in voltage.
  • Current leads voltage by 90º in capacitors (termed ICE).
  • Opposition to AC from a capacitor is known as capacitive reactance (XC).
  • The formula for capacitive reactance: XC = 1 ÷ 2πfC.
  • Capacitive reactance increases as frequency decreases.
  • Capacitive reactance decreases with increasing capacitance.

Total Reactance in AC Circuits

  • Total reactance in a series circuit can be computed using: X = XL - XC or X = XC - XL.
  • Example calculation: if XL is 20 ohms and XC is 50 ohms, total reactance is 30 Ω (capacitive).

Impedance and Power in AC Circuits

  • The total opposition to AC in a circuit is termed impedance (Z).
  • The formula to calculate impedance in a series circuit is: Z = √(R² + X²).
  • In series AC circuits with XL = 6 ohms, XC = 3 ohms, and R = 4 ohms, Z is 5Ω.

Power Concepts

  • True power is the energy consumed by the circuit, measured in watts.
  • Formula for true power: True Power = (IR)²R.
  • Reactive power is the power returned to the source, measured in volt-amperes reactive (var).
  • The formula for calculating reactive power: Reactive Power = (IX)²X.
  • Apparent power represents total power perceived by the circuit, measured in volt-amperes (VA).
  • Apparent power can also be calculated as: √(True Power² + Reactive Power²).

Power Factor

  • Power factor (PF) calculates the efficiency of the circuit, expressed as: PF = True Power ÷ Apparent Power or PF = Cosθ.
  • Desired power factor correction is close to unity (1 or 100%) to minimize losses.
  • If total reactance is inductive, add capacitive reactance; if capacitive, add inductive reactance.

Phase Relationship and Calculations

  • The phase angle (θ) indicates the degree to which current leads or lags voltage.
  • For AC circuits, Ohm's law is represented as: E = IZ or I = E/Z.

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Test your knowledge on the concepts of inductive and capacitive reactance with these flashcards. Learn about the effects of inductors on current changes, phase relationships, and the terminology associated with reactance in AC circuits.

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