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Physics · 2025 · 3 marks
CBSE 2025 · Region 7 · Set 3 · Q27
An ac source of voltage V = V_0 sin ω t is connected to a circuit element X. It is observed that the current flowing through X varies as I = I_0 sin…
An ac source of voltage $\displaystyle \mathrm{V}=\mathrm{V}_{0} \sin \omega \mathrm{t}$ is connected to a circuit element X . It is observed that the current flowing through X varies as $\displaystyle \mathrm{I}=\mathrm{I}_{0} \sin \left(\omega \mathrm{t}-\frac{\pi}{2}\right)$.
(a)
Identify the element X and write the expression for its reactance.
(b)
Plot a graph to show the variation of reactance of the element with the frequency of the applied voltage.
(c)
Draw plots showing the variation of voltage and current with time over one cycle of applied ac.
Marking-scheme solution
(a)
Identifying element X and writing expression for reactance
(b)
Plotting a graph to show variation of reactance with frequency
(c)
Plotting variation of voltage & current with time $\displaystyle 1$
(a)
Inductor
\(\displaystyle \mathrm{X}_{\mathrm{L}}=2 \pi \mathrm{fL}\)
(b)
(c)
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CBSE Class 12 Physics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.