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Physics · 2026 · 3 marks
CBSE 2026 · Region 5 · Set 2 · Q22
(a) Differentiate between inductive reactance, capacitive reactance and impedance of an ac circuit. (b) An ideal inductor and an ideal capacitor are…
(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.
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