PhysicsCBSE Class 12 · Board exam 2025, set 55/1/1 · 1 mark · MCQ

CBSE Class 12 Physics 2025: question 1

Set in the CBSE Class 12 board exam of 2025, paper 55/1/1, section A, question 1, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q1 · 1 mark · MCQElectric Charges and Fields

Figure shows variation of Coulomb force (F) acting between two point charges with $\frac{1}{r ^{2}}$ , r being the separation between the two charges $(q_{1}, q_{2})$ and $(q_{2}, q_{3})$ . If $q_{2}$ is positive and least in magnitude, then the magnitudes of $q_{1}$ , $q_{2}$ and $q_{3}$ are such that

(A) $q_{2} < q_{3} < q_{1}$
(B) $q_{3} < q_{1} < q_{2}$
(C) $q_{1} < q_{2} < q_{3}$
(D) $q_{2} < q_{1} < q_{3}$

Figure in the paper: Graph of F (vertical axis) versus 1/r^2 (horizontal axis). Two straight lines through the origin: the line for (q1, q2) rises with positive slope above the axis; the line for (q2, q3) goes below the axis with negative slope, with smaller steepness. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 55/1/1.

Hints

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

Hint 1

What does the slope of an $F$ versus $1/ r^{2}$ graph represent?

Hint 2

Compare the steepness of the two lines; $q_{2}$ is common to both pairs.

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.

$F = \frac{k q _{a} q _{b}}{r ^{2}}$ , so the slope of the $F$ – $\frac{1}{r ^{2}}$ line is $k q_{a} q_{b}$ . The $(q_{1}, q_{2})$ line is steeper than the $(q_{2}, q_{3})$ line, so $∣ q_{1} q_{2} ∣ > ∣ q_{2} q_{3} ∣$ , which gives $∣ q_{1} ∣ > ∣ q_{3} ∣$ .
½ mark
$q_{2}$ is the least in magnitude, so $q_{2} < q_{3} < q_{1}$ . Option (A).
½ mark

Answer: $q_{2} < q_{3} < q_{1}$ , option (A)

Where the marks are

Uses the slope $\propto q_{a} q_{b}$ to compare the charges and chooses (A) (1 mark)

Revise the chapter

Chapter: Electric Charges and Fields (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Electric Charges and Fields, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 55/1/1: 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.

CBSE Class 12 Physics 2025: question 1

Hints

Step-by-step solution

Revise the chapter

More questions from Electric Charges and Fields