ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 32

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section C, question 32, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q32 · 3 marks · Short answerElectricity

Three resistors of $2 Ω$ , $3 Ω$ and $6 Ω$ are connected in (i) series, and (ii) parallel. Draw the arrangements of the resistors and find the equivalent resistance of each arrangement.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

In series, resistances simply add up.

Hint 2

In parallel, the reciprocals add up. Use the LCM 6 for 1/2 + 1/3 + 1/6.

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.

(i) Series diagram: the 2 Ω, 3 Ω and 6 Ω resistors are joined end to end in a single line between two terminals.
½ mark
In series: $R_{s} = R_{1} + R_{2} + R_{3}$
½ mark
$R_{s} = (2 + 3 + 6) Ω = 11 Ω$
½ mark
(ii) Parallel diagram: the 2 Ω, 3 Ω and 6 Ω resistors are each connected between the same two junction points, forming three separate branches.
½ mark
In parallel: $\frac{1}{R _{p}} = \frac{1}{R _{1}} + \frac{1}{R _{2}} + \frac{1}{R _{3}} = \frac{1}{2} + \frac{1}{3} + \frac{1}{6}$
½ mark
$\frac{1}{R _{p}} = \frac{3 + 2 + 1}{6} = \frac{6}{6} = 1 \Rightarrow R_{p} = 1 Ω$
½ mark

Answer: (i) Series: 11 Ω; (ii) Parallel: 1 Ω

Where the marks are

Series circuit diagram (½ mark)
Series formula (½ mark)
R_s = 11 Ω (½ mark)
Parallel circuit diagram (½ mark)
Parallel formula with substitution (½ mark)
R_p = 1 Ω (½ 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 paper2025 board paper, set 31/2/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.

CBSE Class 10 Science 2025: question 32

Hints

Step-by-step solution

Revise the chapter

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