Semiconductors — KCSE Physics

KCSE Physics · 110 practice questions · 7 syllabus objectives

38 easy35 medium37 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

State examples of semiconductor materials (silicon, germanium) and describe their uses in electronic devices

Distinguish between conductors, semiconductors and insulators in terms of band theory (conduction band and valence band)

Explain the process of doping and distinguish between n-type and p-type semiconductors

Define doping; explain n-type and p-type semiconductors, donor/acceptor impurities, and majority carriers

Distinguish between conductors, semiconductors, and insulators using band theory; describe energy bands

Distinguish between intrinsic and extrinsic semiconductors; explain effect of temperature on intrinsic semiconductors

Semiconductors

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easySHORT ANSWER3 marks

Identify what is meant by 'doping' in semiconductors and explain the roles of donor and acceptor impurities. (3 marks)

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Part (a) — 1 mark

Doping is the intentional introduction of impurities to a semiconductor to enhance its electrical conductivity. (1 mk)

Part (b) — 1 mark

Donor impurities are typically pentavalent atoms that provide extra electrons, increasing the n-type semiconductor's conductivity. (1 mk)

Part (c) — 1 mark

Acceptor impurities are usually trivalent atoms that create holes, increasing the p-type semiconductor's conductivity. (1 mk)

easySHORT ANSWER2 marks

Identify the key differences between intrinsic and extrinsic semiconductors. (2 marks)

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Part (a) — 2 marks

An intrinsic semiconductor is a pure form of semiconductor without impurities (1 mk)

An extrinsic semiconductor contains dopants that enhance its conductivity (1 mk)

easySHORT ANSWER2 marks

Name two characteristics of semiconductors that distinguish them from insulators and conductors. (2 marks)

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Part (a) — 2 marks

Semiconductors have a moderate energy band gap compared to insulators and conductors (1 mk)

Their conductivity increases with temperature, unlike insulators which remain poor conductors (1 mk)

State two common semiconductor materials and describe one application of each in electronic devices. (4 marks)

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