ScienceCBSE Class 10 · Board exam 2023, set 31/1/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 13

Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q13 · 1 mark · MCQElectricity

If four identical resistors, of resistance 8 ohm, are first connected in series so as to give an effective resistance $R_{s}$ , and then connected in parallel so as to give an effective resistance $R_{p}$ , then the ratio $\frac{R _{s}}{R _{p}}$ is

(A)32
(B)2
(C)0.5
(D)16

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Resistances in series simply add.

Hint 2

For n equal resistors R in parallel, $R_{p} = R / n$ .

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

In series: $R_{s} = 8 + 8 + 8 + 8 = 32 Ω$
In parallel: $\frac{1}{R _{p}} = 4 \times \frac{1}{8} = \frac{1}{2}$ , so $R_{p} = 2 Ω$
$\frac{R _{s}}{R _{p}} = \frac{32}{2} = 16$ , which is option (D).
1 mark

Answer: 16; option (D)

Where the marks are

Computes $R_{s} = 32 Ω$ , $R_{p} = 2 Ω$ , ratio 16 (1 mark)

Revise the chapter

Chapter: Electricity (notes, formulas, where marks are lost and every past question)
Topic: Resistors in Series and Parallel

Practise this chapterBoard-style questions from Electricity, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/1/1: every question, by section.

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CBSE Class 10 Science 2023: question 13

Hints

Step-by-step solution

Revise the chapter

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