With increase in frequency of an A.C supply, the impedance of LCR series circuit:

Correct answer: D. First decrease, becomes minimum and then increase

  • A. Decrease
  • B. Increases
  • C. Remains constant
  • D. First decrease, becomes minimum and then increase

Explanation

The correct option, "First decrease, becomes minimum and then increase," describes the behavior of impedance in an LCR series circuit as the frequency of the AC supply increases.Initially, at low frequencies, the inductive reactance (XL) dominates, and the impedance of the circuit increases with frequency. However, as the frequency increases, the capacitive reactance (XC) becomes more significant, causing the total impedance to decrease. At a certain frequency, known as the resonance frequency, the inductive reactance and capacitive reactance cancel each other out, resulting in a minimum impedance. Beyond this frequency, the capacitive reactance dominates, causing the impedance to increase again.

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About Alternating Current

Alternating current varies periodically, so phase relationships become essential when current passes through a resistor, capacitor or inductor. The chapter distinguishes resistance from capacitive and inductive reactance, explains phase lead and lag, and connects changing electric and magnetic fields with the production and properties of electromagnetic waves.

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