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Draw the circuit arrangement… (Class 12 Physics 2023, Q24b)

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PhysicsCBSE Class 12 · Board exam 2023, set 55/1/1 · 2 marks · Very short answer

CBSE Class 12 Physics 2023: question 24(b)

Set in the CBSE Class 12 board exam of 2023, paper 55/1/1, section B, question 24(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q24(b) · 2 marks · Very short answerSemiconductor Electronics: Materials, Devices and Simple Circuits

Draw the circuit arrangement for studying the V – I characteristics of a p-n junction diode in forward bias and reverse bias. Show the plot of V – I characteristic of a silicon diode.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 55/1/1.

Hints

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

Hint 1

In forward bias the p-side goes to the positive terminal of the battery.

Hint 2

Use a milliammeter for forward current and a microammeter for reverse current.

Hint 3

For silicon the forward current rises sharply after about 0.7 V.

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. Forward bias circuit (described): battery through a rheostat/potential divider; p-side of diode connected to positive terminal and n-side to negative; a milliammeter in series with the diode and a voltmeter across it.

    ½ mark

  2. Reverse bias circuit (described): p-side connected to negative terminal and n-side to positive terminal through a potential divider; a microammeter in series and a voltmeter across the diode.

    ½ mark

  3. V–I plot, forward region (described): in the first quadrant, current (mA) is almost zero until the threshold (knee) voltage ≈ 0.7 V for silicon, after which it rises steeply (exponentially) with voltage.

    ½ mark

  4. V–I plot, reverse region (described): in the third quadrant, a very small, nearly constant reverse current (μA) flows with increasing reverse voltage, until at breakdown voltage the reverse current suddenly increases sharply.

    ½ mark

Answer: Forward bias: p to +, n to −, mA meter; reverse bias: p to −, n to +, μA meter. Si characteristic: knee ≈ 0.7 V in forward, tiny μA current then breakdown in reverse.

Where the marks are

  • Forward bias circuit diagram (½ mark)
  • Reverse bias circuit diagram (½ mark)
  • Forward characteristic with knee voltage ≈ 0.7 V (½ mark)
  • Reverse characteristic with small current and breakdown (½ 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 paper2023 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.