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Alternating Current — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsAlternating Current1 Mark
Question
Assertion : An electric lamp connected in series with a variable capacitor and ac source, its brightness increases with increase in capacitance.
Reason : Capacitive reactance decrease with increase in capacitance of capacitor.
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Answer

(a) Capacitive reactance $X_C=\frac{1}{\omega C}$. When capacitance $(C)$ increases, the capacitive reactance decreases. Due to decrease in its values, the current in the circuit will increases $\left(I=\frac{E}{\sqrt{R^2+X_C^2}}\right)$ and hence brightness of source (or electric lamp) will also increases.

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