CBSE 2025 · Region 1 · Set 1 · Q25 · 3 marks
(a)A parallel plate capacitor is charged by an ac source. Show that the sum of conduction current $\displaystyle \left(\mathrm{I}_{\mathrm{c}}\right)$ and the displacement current $\displaystyle \left(\mathrm{I}_{\mathrm{d}}\right)$ has the same value at all points of the circuit.(b)In case (a) above, is Kirchhoff's first rule (junction rule) valid at each plate of the capacitor? Explain.
(a)
A parallel plate capacitor is charged by an ac source. Show that the sum of conduction current $\displaystyle \left(\mathrm{I}_{\mathrm{c}}\right)$ and the displacement current $\displaystyle \left(\mathrm{I}_{\mathrm{d}}\right)$ has the same value at all points of the circuit.
(b)
In case (a) above, is Kirchhoff's first rule (junction rule) valid at each plate of the capacitor? Explain.
Marking-scheme solution
a) Showing that \(\displaystyle \left(\mathrm{I}_{\mathrm{c}}+\mathrm{I}_{\mathrm{d}}\right)\) has the same value.
b) Explanation of Kirchhoff's first rule at each plate of capacitor.
a) ∵ Total current \(\displaystyle \mathrm{I}=\mathrm{I}_{\mathrm{c}}+\mathrm{I}_{\mathrm{d}}\) outside the capacitor
\[\begin{gathered}
\mathrm{I}_{\mathrm{d}}=0 \\
\therefore \mathrm{I}=\mathrm{I}_{\mathrm{c}}
\end{gathered}
\]
Inside the capacitor
\[\mathrm{I}_{\mathrm{c}}=0
\]
Electromagnetic InductionFaraday’s Law of InductionApplyshort_answerhard
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.