For which of the following, a capacitor acts as an infinite resistance component in the circuit?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Direct current
A capacitor opposes current through its capacitive reactance, which depends on the frequency:
\( \displaystyle X_C = \frac{1}{\omega C} = \frac{1}{2\pi\nu C} \)
For direct current \( \nu = 0 \), so \( X_C \rightarrow \infty \). Once the capacitor is charged, no steady current flows through it; it blocks dc.
For alternating current \( \nu \gt 0 \), so \( X_C \) is finite and the current flows through the circuit as the plates charge and discharge.
NCERT (2026-27):
AC Voltage Applied to a Capacitor – “… When a capacitor is connected to a voltage source in a dc circuit, current will flow for the short time required to charge the capacitor. … When the capacitor is fully charged, the current in the circuit falls to zero. When the capacitor is connected to an ac source, as in Fig. 7.7, it limits or regulates the current, but does not completely prevent the flow of charge.”