RL filters in basic AC electronics: depending on where the output is taken (across R or across L) in a simple series RL network driven by a sinusoidal source, the resulting filter can behave as a high-pass or as a low-pass. Confirm or reject this statement.

Introduction / Context:
Passive filters built from a single resistor and a single inductor are common first-order building blocks in AC electronics. Whether such an RL network passes low frequencies or high frequencies depends not just on the parts, but on where the output is measured. This item checks your understanding of output placement and frequency response.

Given Data / Assumptions:

• Series RL network excited by an AC voltage source.
• Ideal components unless otherwise noted (L with no series loss, R purely resistive).
• Output can be taken either across the resistor or across the inductor.
• Small-signal linear operation; no saturation effects.

Concept / Approach:
The frequency-dependent term is the inductive reactance: XL = 2 * π * f * L. At low frequency, XL is small; at high frequency, XL is large. The voltage division between R and XL determines the output. If the output is taken across R, low frequencies appear mostly across R (since XL is small), so the network behaves as a low-pass. If the output is taken across L, high frequencies develop a larger drop across L (since XL grows with f), so the network behaves as a high-pass.

Step-by-Step Solution:

Verification / Alternative check:
Plot magnitude responses of V_R/Vin and V_L/Vin versus frequency. Each is complementary around the corner frequency fc = R / (2 * π * L).

Why Other Options Are Wrong:
Incorrect: contradicts the clear divider behavior described above.
Applies only at resonance: a single RL has no resonance; resonance needs at least L and C.
Valid only for ideal components: small losses slightly alter fc and slope but not the pass/stop nature.

Common Pitfalls:
Confusing RL behavior with RC rules; forgetting that the measured node (R or L) defines which band is passed; assuming “filter type” is fixed by component types alone.

Final Answer:
Correct