Alternating Current
Bihar Board · Class 12 · Physics
Most important questions from Alternating Current for Bihar Board Class 12 Physics board exam 2026. MCQs, short answer, and long answer questions with marks.
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The inductive reactance XL depends on:
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Frequency of AC, Inductance L
Inductive reactance XL = ωL = 2πfL, so it depends directly on both frequency and inductance.
In a purely capacitive circuit, current:
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Leads voltage by 90°
In a capacitor, current leads voltage by π/2 or 90° because current must flow before voltage can build up across the capacitor.
The impedance Z of an RLC series circuit is:
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√[R² + (XL - XC)²]
Impedance is calculated using the Pythagorean theorem from the impedance triangle, with R as one side and (XL - XC) as the other.
At resonance in an RLC circuit:
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XL = XC, Current is maximum, Impedance is minimum
At resonance, XL = XC, so impedance Z = R (minimum), current is maximum, and phase angle is 0°.
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