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Science · 2026 · 3 marks
CBSE 2026 · Region 5 · Set 1 · Q37
(a) Why does an electric bulb become dim when an electric heater in parallel circuit is switched ON? (b) How to connect three resistors each of…
(a)
Why does an electric bulb become dim when an electric heater in parallel circuit is switched ON ?
(b)
How to connect three resistors each of resistance $\displaystyle 8 \Omega$, so that the equivalent resistance of the combination is $\displaystyle 12 \Omega$ ? Draw diagram of the combination and justify your answer.
Marking-scheme solution
(a)
When the electric heater is switched on in a parallel circuit, it
draws a large amount of current. As a result, the current through
the bulb decreases, making the bulb glow dim.
(b)
$\displaystyle \frac{1}{R_{1}}=\frac{1}{8}+\frac{1}{8}$
\[\begin{array}{l}
R_{1}=4 \Omega \\
R_{\mathrm{eq}}=R_{1}+8 \Omega \\
R_{\mathrm{eq}}=12 \Omega
\end{array}
\]
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CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.