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Science · 2024 · 4 marks
CBSE 2024 · Region 3 · Set 1 · Q39
In a domestic circuit five LED bulbs are arranged as shown. The source voltage is $\displaystyle 220$ V and the power rating of each bulb is marked in the circuit diagram. Based on the following circuit diagram, answer the following questions :
(a)State what happens when(i)key $\displaystyle \mathrm{K}_{1}$ is closed.(ii)key $\displaystyle \mathrm{K}_{2}$ is closed.(b)Find the current drawn by the bulb B when it glows.Calculate(i)the resistance of bulb B, and(ii)total resistance of the combination of four bulbs B, C, D and E.What would happen to the glow of all the bulbs in the circuit when keys $\displaystyle \mathrm{K}_{1}$ and $\displaystyle \mathrm{K}_{2}$ both are closed and the bulb C suddenly get fused ? Give reason to justify your answer.
In a domestic circuit five LED bulbs are arranged as shown. The source voltage is $\displaystyle 220$ V and the power rating of each bulb is marked in the circuit diagram. Based on the following circuit diagram, answer the following questions :
(a)
State what happens when
(i)
key $\displaystyle \mathrm{K}_{1}$ is closed.
(ii)
key $\displaystyle \mathrm{K}_{2}$ is closed.
(b)
Find the current drawn by the bulb B when it glows.
Calculate
(i)
the resistance of bulb B, and
(ii)
total resistance of the combination of four bulbs B, C, D and E.
What would happen to the glow of all the bulbs in the circuit when keys $\displaystyle \mathrm{K}_{1}$ and $\displaystyle \mathrm{K}_{2}$ both are closed and the bulb C suddenly get fused ? Give reason to justify your answer.
Marking-scheme solution
(i) Bulb A glows
(ii) Bulbs B, C, D and E glow
(b) \(\displaystyle \mathrm{P}=\mathrm{V} \times \mathrm{I}\)
\[\begin{aligned}
& 11=55 \times \mathrm{I} \\
& \mathrm{I}=\frac{1}{5}=0.2 \mathrm{amp}
\end{aligned}
\]
(c) \[\begin{aligned}
& \text { (i) Resistance of bulb } \mathrm{B}, \mathrm{R}=\frac{V}{I}=\frac{55 \mathrm{~V}}{0.2 \mathrm{~A}}=275 \Omega \\
& \text { (alternative formula for calculation } \mathrm{R}=\frac{V^{2}}{P} \text { ) }
\end{aligned}
\]
Bulb A will keep glowing with same brightness.
Other bulbs i.e., B, D and E will stop glowing.
Reason:
As the bulbs B, D and E are connected in series with fused bulb C, so no current flows through them and thus they will not glow. The bulb A remains unaffected as it is connected in parallel combination.More from Electricity
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CBSE Class 10 Science past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.