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In 2023, researchers… (Class 12 Physics SQP 2026-27, Q29)

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PhysicsCBSE Class 12 · Sample paper, session 2026-27 · 4 marks · Case-based

CBSE Class 12 Physics sample paper 2026-27: question 29

From the official CBSE sample question paper for 2026-27, section D, question 29, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q29 · 4 marks · Case-basedCompetency-basedSemiconductor Electronics: Materials, Devices and Simple Circuits

In 2023, researchers developed flexible semiconductor films using organic polymers that could be printed like newspaper sheets. These films can bend, fold, and still conduct electricity efficiently. Unlike traditional silicon chips, polymer semiconductors are lightweight, biodegradable, and can be integrated into clothing or medical patches. Imagine a shirt that monitors your heartbeat or a bandage that tracks wound healing in real time. Such innovations extend the idea of semiconductors beyond rigid circuits, showing how manipulating band gaps and carrier mobility in new materials can revolutionize electronics for healthcare, sustainability, and wearable technology.

  1. I.

    Which advantage of semiconductors makes them ideal for wearable devices like smart shirts?

    1. (A)High voltage operation (~100 V)
    2. (B)Bulky design and short life
    3. (C)Low power consumption and reliability
    4. (D)Requirement of external heating
    1 mark
  2. II.

    Carbon (diamond) has a band gap of 5.4 eV, while silicon has 1.1 eV. Why is silicon used in electronic devices but not the diamond?

    1. (A)Diamond has too many free electrons.
    2. (B)Diamond’s band gap is too large for thermal excitation at room temperature.
    3. (C)Silicon has weaker covalent bonds than diamond.
    4. (D)Diamond cannot form covalent bonds.
    1 mark
  3. III.

    In an intrinsic semiconductor at room temperature

    1. (A)only electrons contribute to conduction.
    2. (B)only holes contribute to conduction.
    3. (C)number of electrons equals number of holes.
    4. (D)no conduction occurs at all.
    1 mark
  4. IV.

    How will you use the concept of majority and minority carriers to explain the efficiency of polymer semiconductors in wearable technology?

    1 mark

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

For I, think about what a battery-powered shirt needs most.

Hint 2

For II, compare each band gap with kT at room temperature.

Hint 3

For IV, which carriers carry most of the current in a doped material?

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) Wearables run continuously on tiny batteries, so they need devices with low power consumption and high reliability — option (C).

    1 mark

  2. (II) Thermal energy at room temperature (~0.025 eV) can excite electrons across 1.1 eV in Si but practically none across 5.4 eV in diamond, so diamond behaves as an insulator — option (B).

    1 mark

  3. (III) In a pure semiconductor each broken bond gives one free electron and one hole, so — option (C).

    1 mark

  4. (IV) Doped polymer semiconductors carry current mainly by majority carriers (electrons in n-type, holes in p-type) whose concentration and mobility can be controlled, so they conduct well even when bent; minority carriers are few and govern recombination. Hence a useful current flows at low voltage and low power, making them efficient for flexible wearable devices.

    1 mark

Answer: I. (C); II. (B); III. (C); IV. Conduction by controllable majority carriers gives efficient low-power conduction in flexible films.

Where the marks are

  • I: option C (1 mark)
  • II: option B (1 mark)
  • III: option C (1 mark)
  • IV: majority carriers carry current, controllable concentration/mobility → efficient low-power conduction (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Semiconductor Electronics: Materials, Devices and Simple Circuits, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: 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.