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The following graph… (Class 12 Physics SQP 2025-26, Q18)

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PhysicsCBSE Class 12 · Sample paper, session 2025-26 · 2 marks · Very short answer

CBSE Class 12 Physics sample paper 2025-26: question 18

From the official CBSE sample question paper for 2025-26, section B, question 18, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q18 · 2 marks · Very short answerCompetency-basedCurrent Electricity

The following graph shows the potential difference across the terminals of a cell against its load current.

Find,
(I) the emf of the cell and
(II) the internal resistance of the cell.

Figure in the paper: Graph of potential difference (V, vertical, 0-6) against load current (A, horizontal, 0-12): a straight line falling from 6 V at 0 A to 0 V at 12 A. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

Use the relation .

Hint 2

What is V when no current is drawn?

Hint 3

The magnitude of the slope of the V–I graph equals r.

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) The terminal voltage is . When the load current , . From the graph, V at , so emf V.

    1 mark

  2. (II) The slope of the – line is : slope . Hence internal resistance . (Check: at , A.)

    1 mark

Answer: (I) emf = 6 V; (II) r = 0.5 Ω

Where the marks are

  • Reads emf as 6 V from the intercept at zero current, with reason (1 mark)
  • Finds internal resistance from the slope, (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Current Electricity, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26: 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.