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NEET PHYSICSALTERNATING CURRENTMedium

Question

A light bulb and an inductor coil are connected to an AC source through a key as shown in the figure below. The key is closed and after some time an iron rod is inserted into the interior of the inductor. The glow of the light bulb:

A

decreases

B

remains unchanged

C

will fluctuate

D

increases

Step-by-Step Solution

Inserting an iron rod into the inductor increases its self-inductance (LL) because iron has a high relative permeability (μr\mu _r) . The inductive reactance of the coil is defined as XL=ωLX_L = \omega L; therefore, an increase in LL leads to an increase in XLX_L . In a series circuit containing a light bulb (resistor RR) and an inductor, the total impedance is Z=R2+XL2Z = \sqrt{R^2 + X_L^2} . As XLX_L increases, the total impedance ZZ of the circuit also increases. Since the RMS current is I=Vrms/ZI = V_{rms}/Z, the increased impedance causes the current to decrease . Because the brightness (glow) of the bulb depends on the power dissipated (P=I2RP = I^2R), a reduction in current results in the glow of the bulb decreasing .

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 CURRENTinductorconnectedsourcethroughfigure

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