JEE PHYSICS MCQ: ALTERNATING CURRENT

Solution approach

1. Correct Answer + Core Reason: The current and the PD across the resistance lag behind the PD across the inductance by an angle $\pi / 2$. In an RL series circuit, the voltage across the inductor leads the current by 90 degrees, while the voltage and current across the resistor are in phase.
   
   Step-by-Step Solution:
   
   Step 1: In a resistor, the voltage and current are in phase.
   
   Step 2: In an inductor, the voltage leads the current by $\pi/2$ (90 degrees).
   
   Step 3: In a series RL circuit, the same current flows through both the resistor and the inductor.
   
   Step 4: Since the voltage across the inductor leads the current by $\pi/2$, and the voltage across the resistor is in phase with the current, the voltage across the resistor lags behind the voltage across the inductor by $\pi/2$.
   
   Why other options are wrong:
   - Option A: The current and the PD across the resistance lead the PD across the inductance is incorrect because the voltage across the inductor leads the current.
   - Option C: The current and the PD across the resistance lag behind the PD across the inductance by an angle $\pi$ is incorrect because the phase difference is $\pi/2$.
   - Option D: The PD across the resistance lags behind the PD across the inductance by an angle $\pi / 2$ but the current in resistance leads the PD across the inductance by $\pi / 2$ is incorrect because the current in the resistance is in phase with the voltage across the resistance.
   
   Key Concepts:
   - AC Circuits
   - Resistors
   - Inductors
   - Phase Difference
   - Voltage and Current Relationships
   
   Memory Aids:
   - ELI the ICE man: E leads I in an inductor (L), I leads E in a capacitor (C).
   
   Quick Tips:
   - Remember the phase relationships between voltage and current in resistors and inductors.