Skip to content

Consider a rectangular… (Class 10 Science 2025, Q32)

questionbuddy.in/q/cbse-10-science-2025-31-3-1-q32-consider-rectangular-cardboard-having-holes

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

CBSE Class 10 Science 2025: question 32

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

Q32 · 3 marks · Short answerMagnetic Effects of Electric Current

Consider a rectangular cardboard having two holes P and Q through which a current carrying circular loop has been inserted as shown in the diagram.

  1. (a)

    Make this diagram on your answer sheet and draw three magnetic field lines, one each passing through the points 1 (near P), 2 (at the centre of the loop) and 3 (near Q).

    1 mark
  2. (b)

    List two factors on which the intensity of the magnetic field produced at the centre of the loop depends.

    1 mark
  3. (c)

    Name the rule you will apply to determine the direction of magnetic field produced due to a current carrying straight conductor.

    1 mark

Figure in the paper: A rectangular cardboard (shown in perspective) with two small holes P (left) and Q (right). A circular loop passes through the holes: the upper semicircle is drawn above the cardboard as a solid arc and the lower semicircle is dashed below the cardboard. A dashed horizontal line joins P and Q through the centre of the loop, with three marked points: 1 near P, 2 at the centre, and 3 near Q. Two wire leads at the bottom front of the cardboard carry current, with arrows showing current going up on one lead and down on the other. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/3/1.

Hints

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

Hint 1

Near each hole the wire behaves like a straight conductor.

Hint 2

At the centre, all parts of the loop produce fields in the same direction.

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. (a) Point 1 (near P): field lines are small concentric circles around the wire at P, direction given by the right-hand thumb rule for the current there.

    ½ mark

  2. Point 3 (near Q): concentric circles around the wire at Q in the opposite sense, since current at Q flows in the opposite direction (down vs up through the board).

    ½ mark

  3. Point 2 (centre): the field line is nearly a straight line, perpendicular to the plane of the loop, as fields from all parts of the loop add up in the same direction.

    ½ mark

  4. (b) Factor 1: strength of current in the loop (field ∝ current).

    ½ mark

  5. Factor 2: number of turns of the loop (also radius – field decreases as radius increases).

    ½ mark

  6. (c) Right-hand thumb rule.

    ½ mark

Answer: (a) Circles around P and Q in opposite senses, straight line at centre; (b) current and number of turns (also radius); (c) right-hand thumb rule

Where the marks are

  • Correct field lines at points 1, 2 and 3 (½ × 3 marks)
  • Two factors: current, number of turns (½ × 2 marks)
  • Right-hand thumb rule (½ 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 paper2025 board paper, set 31/3/1: 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.