Rankers Physics

Alternating Current: Practice Problem & Solution

15. A series RC circuit is connected to an alternating voltage source. Consider two situations A. When capacitor is air filled. B. When capacitor is mica filled. Current through resistor is i and voltage across capacitor is V then: (2015 Re)
$V_a = V_b$
$V_a < V_b$
$V_a > V_b$
$I_a > I_b$

Solution Explained:

To solve this problem, we apply the core principles of Alternating Current. Understanding the underlying formula is key to arriving at the correct answer below:

Inserting mica increases capacitance ($C_b > C_a$), so reactance decreases ($X_{Cb} i_a$). Since $V_C = \frac{V}{\sqrt{1 + (R/X_C)^2}}$, as $X_C$ decreases, $V_C$ decreases, hence $V_a > V_b$.

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