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NEET PHYSICSALTERNATING CURRENTMedium

Question

As the frequency of an AC circuit increases, the current first increases and then decreases. Which of the following combinations of circuit elements is most likely to comprise the circuit? (a) Inductor and capacitor (b) Resistor and inductor (c) Resistor and capacitor (d) Resistor, inductor, and capacitor

A

(b), (c)

B

(c), (d)

C

(b), (d)

D

(a), (d)

Step-by-Step Solution

The behavior where current first increases and then decreases as frequency increases is the characteristic of electrical resonance in a series AC circuit. According to the sources, the current magnitude is I=V/ZI = V / Z, where the impedance Z=R2+(XL−XC)2Z = \sqrt{R^2 + (X_L - X_C)^2} . Inductive reactance (XL=ωLX_L = \omega L) increases with frequency, while capacitive reactance (XC=1/ωCX_C = 1/\omega C) decreases . At very low frequencies, XCX_C is very large, making current small. At the resonant frequency (f0=1/(2πLC)f_0 = 1/(2\pi\sqrt{LC})), XL=XCX_L = X_C, the impedance is at its minimum (Z=RZ=R), and current is at its maximum . At very high frequencies, XLX_L becomes very large, causing the current to decrease again. This 'peaking' behavior requires both inductance (L) and capacitance (C) to be present in the circuit. Therefore, combinations (a) and (d) are the correct answers.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from ALTERNATING CURRENT. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSALTERNATING CURRENTfrequencycircuitincreasescurrentincreases

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