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Answer the following. (Science 2025 31/2/1 Q36b)

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ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 5 marks · Long answer

CBSE Class 10 Science 2025: question 36(b)

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section D, question 36(b), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q36(b) · 5 marks · Long answerMagnetic Effects of Electric Current

Answer the following.

  1. (i)

    Define the term solenoid. Draw the pattern of the magnetic field lines in and around a current carrying straight solenoid. Mark on the pattern the (i) direction of current, (ii) direction of field lines near the ends of the solenoid, and (iii) region where the magnetic field is uniform.

    0 marks
  2. (ii)

    How would you make an electromagnet using a current carrying solenoid?

    0 marks

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

Think of a long spring-shaped coil of wire.

Hint 2

Its field pattern looks like that of which common magnet?

Hint 3

Which material is easily magnetised and demagnetised when placed inside the coil?

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) Definition: A solenoid is a coil of many circular turns of insulated copper wire, wrapped closely in the shape of a cylinder.

    1 mark

  2. (i) Diagram: Draw a cylindrical coil connected to a battery. Inside it, draw straight, parallel, equally spaced field lines along the axis. Outside, the lines curve from one end round to the other, like those of a bar magnet, with one end acting as N and the other as S.

    1½ marks

  3. (i) Marking: (1) Arrows on the turns show the direction of current, entering at one end from the battery. (2) Arrows on the field lines show them coming out of the N end and entering the S end; inside the solenoid they run from S to N. (3) The region inside the solenoid, where the lines are straight and parallel, is labelled as the region of uniform magnetic field.

    1½ marks

  4. (ii) Place a piece of soft iron (a magnetic material) inside the solenoid and pass current through it. The strong field inside magnetises the soft iron, which then acts as an electromagnet as long as the current flows.

    1 mark

Answer: (i) A solenoid is a closely wound cylindrical coil of many turns of insulated copper wire. Its field resembles a bar magnet's and is uniform inside. (ii) Insert a soft iron core inside the current-carrying solenoid.

Where the marks are

  • Correct definition of solenoid (1 mark)
  • Correct field pattern diagram (1½ marks)
  • Marks current direction, field direction at the ends, and uniform-field region (½ mark each, 1½ marks)
  • Inserting a soft iron core makes an electromagnet (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 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.