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(i) Draw a diagram showing… (Class 10 Science 2026, Q39A)

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ScienceCBSE Class 10 · Board exam 2026, set 31/5/1 · 5 marks · Long answer

CBSE Class 10 Science 2026: question 39(A)

Set in the CBSE Class 10 board exam of 2026, paper 31/5/1, section C, question 39(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q39(A) · 5 marks · Long answerMagnetic Effects of Electric Current

(i) Draw a diagram showing the magnetic field lines around a bar magnet. Write any two characteristics of magnetic field lines.
(ii) Write the statement of Right hand thumb rule.
(iii) The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. How does magnetic field change on these concentric circles ?

  1. (i)

    Draw a diagram showing the magnetic field lines around a bar magnet. Write any two characteristics of magnetic field lines.

    0 marks
  2. (ii)

    Write the statement of Right hand thumb rule.

    0 marks
  3. (iii)

    The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. How does magnetic field change on these concentric circles ?

    0 marks

Figure in the paper: Diagram of a bar magnet showing magnetic field lines emerging from the North pole and entering the South pole, with lines drawn closer together near the poles. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/5/1.

Hints

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

Hint 1

Think about which pole the lines leave and which they enter.

Hint 2

Why can field lines never intersect, and what does their spacing indicate?

Hint 3

For (iii), how does field strength depend on distance from the wire?

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. (i) Diagram: Draw a bar magnet with N and S marked. Draw closed curved field lines coming out of the N pole and entering the S pole outside the magnet, with arrows; lines are crowded near the poles and spread out away from them; inside the magnet arrows go from S to N.

    1 mark

  2. Characteristic 1: Field lines emerge from the north pole and merge at the south pole outside the magnet, and go from south to north inside, so they are closed curves.

    1 mark

  3. Characteristic 2: No two field lines cross each other (otherwise there would be two directions of the field at one point). [Also: closeness of lines shows relative strength of field.]

    1 mark

  4. (ii) Right-hand thumb rule: Hold the current-carrying straight conductor in the right hand with the thumb pointing along the direction of current; the direction in which the fingers curl around the conductor gives the direction of the magnetic field lines.

    1 mark

  5. (iii) The magnetic field becomes weaker (decreases) on the larger circles, i.e. it decreases as the distance from the wire increases ().

    1 mark

Answer: (i) Diagram + closed curves N→S outside, lines never cross; (ii) thumb along current, fingers give field direction; (iii) field decreases on larger circles

Where the marks are

  • Correct diagram of field lines around bar magnet with arrows (1 mark)
  • Any two correct characteristics (1 + 1 marks)
  • Correct statement of right-hand thumb rule (1 mark)
  • Field decreases as circles get larger (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Magnetic Effects of Electric Current, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/5/1: 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.