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The given figure shows the… (Class 10 Science 2025, Q36a)

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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(a)

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

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

The given figure shows the current passing through the straight conductor XY.

  1. (i)

    Copy the diagram and draw the magnetic field lines when current flows from conductor X to Y.

    0 marks
  2. (ii)

    Name and state the rule used in determining the direction of the magnetic field lines in the situation given above.

    0 marks
  3. (iii)

    State Fleming's left hand rule. Using this rule, determine the direction of force applied on an electron entering a uniform magnetic field as shown in the figure.

    0 marks

Figure in the paper: Circuit: a variable resistance, ammeter (A) with + and − terminals, a battery and a key K are connected in series. A straight vertical conductor XY passes through the centre of a rhombus-shaped loop labelled Q; X is at the top with an arrow pointing downward, Y is at the bottom. Current is shown flowing from X to Y through the wire. (iii) figure: three horizontal arrows pointing right representing a uniform magnetic field; an electron 'e' moving vertically upward (arrow pointing up) enters the field region. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

The field around a straight wire forms circles in the plane perpendicular to the wire.

Hint 2

Point your right thumb along the current; your fingers show the field.

Hint 3

The current due to a moving electron is opposite to its motion; then apply the left-hand rule.

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 several concentric circles on the horizontal plane Q, centred on the wire XY, spaced farther apart as they move away from the wire. Current flows downward from X to Y. Seen from above, the current is going away from the viewer, so the arrows on the field lines point clockwise.

    1½ marks

  2. (ii) Name: Right-hand thumb rule.

    ½ mark

  3. (ii) Statement: Imagine holding the current-carrying straight conductor in your right hand so that the thumb points in the direction of the current. The direction in which your fingers curl around the conductor gives the direction of the magnetic field lines.

    1 mark

  4. (iii) Fleming's left-hand rule: Stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular. If the forefinger points along the magnetic field and the middle finger along the current, the thumb points in the direction of the force (motion) on the conductor.

    1 mark

  5. (iii) The electron moves upward, so the conventional current is downward. The field points to the right. With the forefinger to the right and the middle finger pointing down, the thumb points out of the plane of the paper (towards the reader).

    1 mark

Answer: (i) Concentric circles around XY, clockwise as seen from above. (ii) Right-hand thumb rule. (iii) The force on the electron is perpendicular to the plane of the paper, directed outward (towards the reader).

Where the marks are

  • Concentric circular field lines with correct (clockwise from top) direction (1½ marks)
  • Names the right-hand thumb rule (½ mark)
  • States the right-hand thumb rule correctly (1 mark)
  • States Fleming's left-hand rule correctly (1 mark)
  • Force on electron: out of the plane of paper (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.