Question

The capacity of a pure capacitor is $1farad$. In dc circuits, its effective resistance will be?

• A. $0.5ohm$
• B. $1ohm$
• C. Infinite
• D. Zero

Answer 1

The correct option is C

Infinite

Step 1: Given data

Capacity of a pure capacitor, $C=1farad$

Step 2: State the capacitive reactance

Capacitive reactance is given by,

$X_C=\frac{1}{2\mathrm{\pi vC}}$

Where, $X_C$ is the capacitive reactance, $v$ is the frequency, and $C$ is the capacitance.

Step 3: Determine its effective resistance in DC

$$\begin{gathered} X_C=\frac{1}{2\mathrm{\pi vC}} \\ =\frac{1}{2\mathrm{\pi }\times 0\times 1} \\ =\frac{1}{0} \\ =\infty \end{gathered}$$

(The frequency of a DC circuit is zero, $\nu =0$)

Therefore, option C is the correct option.