The phase difference between the alternating current and emf is π/2. Which of the following cannot be the constituent of the circuit? (a) R, L (b) C alone (c) L alone (d) L, C

Answer: (a). A phase difference of exactly π/2 needs a purely reactive circuit ( R = 0). C alone, L alone, or L and C (with XL ≠ XC) all give φ = π/2. With R and L: tan φ = XL/R is finite, so φ < π/2. So the answer is (a) R, L.

The phase difference between the alternating current and emf is π/2… | JEE Main 2005 (AIEEE)

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Series LCR Circuit

The phase difference between the alternating current and $emf$ is $\frac{\pi}{2}.$ Which of the following cannot be the constituent of the circuit?

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Answer: (a)

A phase difference of exactly $\dfrac{\pi}{2}$ needs a purely reactive circuit ( $R = 0$ ).
C alone, L alone, or L and C (with $X_L \ne X_C$ ) all give $\phi = \dfrac{\pi}{2}$ .
With $R$ and $L$ : $\tan\phi = \dfrac{X_L}{R}$ is finite, so $\phi < \dfrac{\pi}{2}$ .
So the answer is (a) $R, L$ .

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