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Answer the following. (Science 2026 31/3/1 Q39a)

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ScienceCBSE Class 10 · Board exam 2026, set 31/3/1 · 5 marks · Long answer

CBSE Class 10 Science 2026: question 39(a)

Set in the CBSE Class 10 board exam of 2026, paper 31/3/1, 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

Answer the following.

  1. (i)

    What is a solenoid ? Draw a diagram showing the magnetic field pattern due to a current-carrying solenoid (inside and outside).

    0 marks
  2. (ii)

    Name any two factors on which the magnitude of the magnetic field due to a current-carrying solenoid depends.

    0 marks
  3. (iii)

    A current-carrying solenoid is stretched and converted into a straight wire carrying current. Draw a diagram showing the magnetic field pattern around it and mark the direction of the magnetic field.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/3/1.

Hints

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

Hint 1

A solenoid looks like a spring made of wire. Describe its shape.

Hint 2

Its field resembles a bar magnet's field. What do the lines look like inside the coil?

Hint 3

For a straight wire, use the right-hand thumb rule to decide which way the circular lines run.

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) A solenoid is a coil of many circular turns of insulated copper wire wound closely in the shape of a cylinder.

    1 mark

  2. (i) Diagram (described): draw a cylindrical coil connected to a battery, with the current direction marked in the turns.

    • Inside: draw parallel, equally spaced straight field lines along the axis, showing a uniform field.
    • Outside: draw closed lines running from one end to the other, like a bar magnet's field.
    • Mark the N end (where the lines emerge) and the S end (where they enter), with arrows from N to S outside and from S to N inside.
    2 marks

  3. (ii) Factor 1: the magnitude of the current flowing through the solenoid.

    ½ mark

  4. (ii) Factor 2: the number of turns of the coil.

    ½ mark

  5. (iii) Field around a straight current-carrying wire (described): draw a vertical straight wire passing through a horizontal card, with the current marked upward. Around the wire on the card, draw concentric circles centred on it, with the spacing increasing outward. For upward current, mark the circles with arrows anticlockwise as seen from above, by the right-hand thumb rule. Any current direction is acceptable if the field direction matches it.

    1 mark

Answer: (i) Closely wound cylindrical coil of insulated copper wire; uniform parallel field lines inside, bar-magnet-like field outside. (ii) Current and number of turns. (iii) Concentric circles around the wire, with direction by the right-hand thumb rule.

Where the marks are

  • Definition of solenoid (1 mark)
  • Correct field pattern of the solenoid inside (parallel lines) and outside, with directions/poles (2 marks)
  • Factor: current (½ mark)
  • Factor: number of turns (½ mark)
  • Concentric circular field lines around the straight wire, with the correct direction for the current shown (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 31/3/1: 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.