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With the help of… (Class 12 Physics SQP 2025-26, Q22)

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PhysicsCBSE Class 12 · Sample paper, session 2025-26 · 3 marks · Short answer

CBSE Class 12 Physics sample paper 2025-26: question 22

From the official CBSE sample question paper for 2025-26, section C, question 22, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q22 · 3 marks · Short answerSemiconductor Electronics: Materials, Devices and Simple Circuits

With the help of circuit diagram explain working of the full wave rectifier.

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 a centre-tapped transformer and two diodes.

Hint 2

In each half cycle, ask which end of the secondary is positive and which diode is forward biased.

Hint 3

Check the direction of current through the load in both half cycles.

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. Circuit: AC input is applied to the primary of a centre-tapped transformer. The two ends A and B of the secondary are connected to the p-sides of diodes and ; their n-sides are joined at point Q. The load resistance is connected between Q and the centre tap P, and output is taken across .

    1 mark

  2. During one half cycle, end A is positive with respect to the centre tap: is forward biased and conducts, is reverse biased. Current flows through from Q to P.

    1 mark

  3. During the next half cycle, end B becomes positive: is forward biased and conducts while is reverse biased. Current again flows through in the same direction (Q to P). Thus output is obtained in both half cycles — a pulsating unidirectional (DC) voltage, with output waveform showing a positive hump for every half cycle of the input.

    1 mark

Answer: Centre-tap full wave rectifier: D1 and D2 conduct alternately, current through load in the same direction in both half cycles, giving pulsating DC

Where the marks are

  • Correct labelled circuit diagram with centre-tapped transformer, two diodes and load (1 mark)
  • Working in first half cycle (1 mark)
  • Working in second half cycle and unidirectional output waveform (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 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.