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QPages 328-329: Q6: HC Verma: Concepts of Physics - Volume 2 Alternating Current Pages 328-329: Q6 Solution: An AC source is connected to a capacitor. Will the rms current…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often think that inserting a dielectric reduces the electric field and therefore reduces current, but in AC the current is governed by the capacitive reactance $X_C= rac{1}{omega C}$. Since $C$ increases, $X_C$ decreases, so $I_{ ext{rms}}= rac{V_{ ext{rms}}}{X_C}$ actually increases. Always use the reactance formula, not the DC charging intuition, when evaluating AC current changes.

An AC source is connected to a capacitor. Will the rms current increase, decrease or remain constant if a dielectric slab is inserted into the capacitor?

Step-by-Step Verified Solution

**Answer:** Increase. **Step-by-Step Explanation:** Inserting a dielectric slab increases the capacitance (C′=KCC' = KC, where K>1K > 1). The reactance XC=1ωCX_C = \frac{1}{\omega C} decreases. Since Irms=VrmsXCI_{rms} = \frac{V_{rms}}{X_C}, a decrease in reactance leads to an increase in the rms current [citation:1][citation:14][citation:16].

All Questions in this Chapter

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