CBSE 2026 · Region 5 · Set 2 · Q22 · 3 marks
(a)Differentiate between inductive reactance, capacitive reactance and impedance of an ac circuit.(b)An ideal inductor and an ideal capacitor are connected in series across an ac voltage. Plot a graph showing variation of net reactance of the circuit with frequency of the applied ac voltage.
(a)
Differentiate between inductive reactance, capacitive reactance and impedance of an ac circuit.
(b)
An ideal inductor and an ideal capacitor are connected in series across an ac voltage. Plot a graph showing variation of net reactance of the circuit with frequency of the applied ac voltage.
Marking-scheme solution
(a)
Inductive reactance — it is the opposition to the flow of ac current by an inductor. (Alternatively: $\displaystyle X_{L}=\omega L$)
Capacitive reactance — it is the opposition to the flow of ac current by a capacitor. (Alternatively: $\displaystyle X_{C}=\dfrac{1}{\omega C}$)
Impedance — the effective opposition offered by a combination of inductor, capacitor and resistor to the flow of ac current. (Alternatively: $\displaystyle Z=\sqrt{R^{2}+\left(X_{L}-X_{C}\right)^{2}}$)
(b)
Plot of net reactance against $\displaystyle \omega$: large and positive at low frequency, falling through zero at the resonant frequency $\displaystyle \omega_{r}$, and negative beyond it.
Alternating CurrentAC Voltage Applied to a Series LCR CircuitAnalyseshort_answermedium
More from Alternating Current
- An alternating current is given by I=I 0 cos (100 π) t. The least time the current takes to decrease from its…2025 · asked 3×
- A resistor of 30 Ω and a capacitor of 250/(π) μ F are connected in series to a 200 V, 50 Hz ac source.…2023 · asked 3×
- An inductor, a capacitor and a resistor are connected in series across an ac source of voltage. If the…2023 · asked 3×
- Assertion: A series LCR circuit behaves as a pure resistive circuit at resonance. Reason (R): At resonance, X…2025 · asked 3×
- How does the resistance differ from impedance? With the help of a suitable phasor diagram, obtain an…2023 · asked 3×
- Assertion: In an ideal step-down transformer, the electrical energy is not lost. Reason (R): In a step-down…2025 · asked 3×
- An ac voltage is given as v=14 sin (314 t) V. The average and the effective value of the voltage (in V ) over…2026 · asked 3×
- The figure shows the variation of capacitive reactance (X C) of two ideal capacitors of capacitances C 1 \& C…2026 · asked 3×
CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.