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Science · 2023 · 5 marks
CBSE 2023 · Region 5 · Set 2 · Q34
There are three resistors of 10 Ω, 20 Ω and 30 Ω joined in parallel in a circuit. The potential difference across the electric circuit is 10 V. (a)…
There are three resistors of $\displaystyle 10 \Omega, 20 \Omega$ and $\displaystyle 30 \Omega$ joined in parallel in a circuit. The potential difference across the electric circuit is $\displaystyle 10$ V.
(a)
Draw a circuit diagram for the above case.
(b)
Find the total resistance of the combination of resistors.
(c)
Calculate the electric current drawn from the same source.
Marking-scheme solution
(a) 
(b) \(\displaystyle \frac{1}{\mathrm{R}}=\frac{1}{\mathrm{R}_{1}}+\frac{1}{\mathrm{R}_{2}}+\frac{1}{\mathrm{R}_{3}}\)
\(\displaystyle =\frac{1}{10}+\frac{1}{20}+\frac{1}{30}\)
\[=\frac{6+3+2}{60}
\]
\(\displaystyle \therefore \mathrm{R}=\frac{60}{11} \Omega \quad / 5.45 \Omega\)
(c) \(\displaystyle \mathrm{I}=\frac{\mathrm{V}}{\mathrm{R}}\)
\(\displaystyle \mathrm{I}=\frac{10 \mathrm{~V}}{\dfrac{60}{11} \Omega}=\frac{110}{60} \mathrm{~A}=1.83 \mathrm{~A}\)
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.