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Mona was doing an… (Class 10 Science SQP 2024-25, Q33)

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ScienceCBSE Class 10 · Sample paper, session 2024-25 · 3 marks · Short answer

CBSE Class 10 Science sample paper 2024-25: question 33

From the official CBSE sample question paper for 2024-25, section C, question 33, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q33 · 3 marks · Short answerMagnetic Effects of Electric Current

Mona was doing an experiment with a magnetic compass and a straight current-carrying wire. She observed that as she moved the compass away from the current-carrying wire, the deflection of the compass needle reduced.
A. Explain why the deflection of the compass needle reduced as Mona moved away the compass needle from the current carrying wire.
B. Mention one thing that could have changed in the circuit of the wire that could increase the deflection of the needle.
C. Explain with reason what will be the direction of the magnetic field associated with the wire for the case described by the above figure.

(For visually impaired students: A. Explain why the deflection of the compass needle reduced as Mona moved away the compass needle from the current carrying wire. B. Mention one thing that could have changed in the circuit of the wire that could increase the deflection of the needle. C. Explain with reason how the direction of the magnetic field associated with the wire changes if the polarity of battery reversed.)

Figure in the paper: A flat horizontal board with a compass needle on it; a rectangular wire loop circuit with a battery passes vertically through the board. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

How does the strength of the magnetic field around a wire depend on distance?

Hint 2

Which quantity in the circuit, if increased, gives a stronger field?

Hint 3

Use the right-hand thumb rule: thumb along the current, fingers show the field.

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. The magnetic field produced by a straight current-carrying wire is inversely proportional to the distance from the wire. As the compass moves away, the field acting on it becomes weaker, so the deflection decreases.

    1 mark

  2. B. The field is directly proportional to the current. Increasing the current (for example, by using a battery of higher voltage or reducing the circuit resistance) would increase the deflection.

    1 mark

  3. C. From the battery's polarity, the current in the vertical wire flows from the top of the board downwards. By the right-hand thumb rule, point the thumb along the current (downwards); the curled fingers then give the field lines as concentric circles that are clockwise when viewed from above the board.

    1 mark

  4. (For visually impaired students) C. If the battery's polarity is reversed, the current in the wire reverses, so the direction of the magnetic field also reverses (clockwise becomes anticlockwise).

Answer: A. Field weakens with distance (B ∝ 1/r); B. Increase the current; C. Current downward, so field is clockwise (seen from above) by the right-hand thumb rule.

Where the marks are

  • Field strength decreases with distance from the wire (1 mark)
  • Increase current to increase deflection (1 mark)
  • Uses the right-hand thumb rule with the current direction to state the field is clockwise (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 paperSample paper 2024-25: 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.