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Two wires A and B of same… (Class 10 Science 2024, Q26)

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ScienceCBSE Class 10 · Board exam 2024, set 31/4/1 · 2 marks · Very short answer

CBSE Class 10 Science 2024: question 26

Set in the CBSE Class 10 board exam of 2024, paper 31/4/1, section B, question 26, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q26 · 2 marks · Very short answerElectricity

Two wires A and B of same material, having same lengths and diameters mm and mm respectively, are connected one by one in a circuit. Which one of these two wires will offer more resistance to the flow of current in the circuit ? Justify your answer.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/4/1.

Hints

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

Hint 1

Write the formula for resistance in terms of resistivity, length and area.

Hint 2

Which wire has the smaller area of cross-section?

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.

  1. Wire A (diameter 0.2 mm) offers more resistance.

    1 mark

  2. Justification: . For the same material and length, , and , so . Hence . The thinner wire A has the smaller area of cross-section, so it has the greater resistance.

    1 mark

Answer: Wire A, because resistance is inversely proportional to area of cross-section (R_A = 2.25 R_B).

Where the marks are

  • Identifies wire A (1 mark)
  • Justifies using R ∝ 1/A, i.e. the thinner wire has more resistance (1 mark)

Revise the chapter

  • Chapter: Electricity (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Electricity, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/4/1: 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.