Capacitor behavior with AC and DC – Which does it block? Statement: “A capacitor blocks AC but passes DC.” Determine if this is correct for an ideal capacitor.

Introduction / Context:
Signal coupling and decoupling rely on the opposite behaviors of capacitors for AC and DC. Getting this principle wrong flips the intended function of coupling capacitors, DC blocks, and bypass networks.

Given Data / Assumptions:

• Ideal capacitor with impedance Xc = 1/(ωC).
• DC means ω = 0 rad/s; AC means ω > 0.
• No leakage or parasitic inductance considered for the core concept.

Concept / Approach:

At DC (ω = 0), Xc → ∞, so the capacitor behaves as an open circuit: it blocks DC. At high frequency, Xc becomes small, allowing AC to pass. Therefore, the statement is reversed and is false.

Step-by-Step Solution:

Verification / Alternative check:

Observe common circuits: coupling capacitors insert series C to remove DC offset while allowing signals; bypass capacitors shunt AC ripple to ground while leaving DC levels intact.

Why Other Options Are Wrong:

Electrolytic type, “cutoff frequency,” or ESR do not change the ideal rule; they only affect the practical band over which AC is effectively coupled.

Common Pitfalls:

Confusing inductors with capacitors (inductors pass DC and impede AC at high frequency); misinterpreting “blocking” in series versus shunt placements.

Final Answer:

False.