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OJEE Semiconductor Devices — practice questions

Explore 20 free Semiconductor Devices questions in OJEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Semiconductor Devices questions and exercises with answers

Showing questions 1–20 of 20.

Conductivity of a material is highest in:Read the answer and worked solution →Energy gap (band gap) of pure silicon at room temperature:Read the answer and worked solution →In an intrinsic (pure) semiconductor at T > 0:Read the answer and worked solution →n-type semiconductor is doped with:Read the answer and worked solution →p-type semiconductor is doped with:Read the answer and worked solution →A diode allows current to flow:Read the answer and worked solution →For forward bias of p-n diode:Read the answer and worked solution →Zener diode is operated in:Read the answer and worked solution →A diode in half-wave rectifier produces output for:Read the answer and worked solution →In a transistor (npn), the emitter is:Read the answer and worked solution →For NAND gate: output is 0 when:Read the answer and worked solution →Solar cell converts:Read the answer and worked solution →Intrinsic carrier concentration of Si at 300 K is approximately:Read the answer and worked solution →In doped semiconductor at thermal equilibrium: n_e × n_h =Read the answer and worked solution →Common-emitter transistor with β = 100 has base current 50 μA. Collector current:Read the answer and worked solution →For a full-wave bridge rectifier with AC input V_rms, peak DC output voltage:Read the answer and worked solution →Truth table for AND gate (2 inputs): output is 1 when:Read the answer and worked solution →For NPN transistor in active mode, base-emitter junction is ___ and base-collector is ___:Read the answer and worked solution →n-type or p-type?Read the answer and worked solution →True or false: semiconductorsRead the answer and worked solution →

Worked practice questions

Conductivity of a material is highest in:

  1. Semiconductor
  2. Vacuum
  3. Insulator
  4. Metal (conductor)
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Correct answer: D. Metal (conductor)

Metals have very high conductivity (~10⁷ S/m) due to free electrons. Semiconductors are intermediate (10⁻⁴ to 10⁴ S/m), insulators very low (<10⁻⁸ S/m).

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Energy gap (band gap) of pure silicon at room temperature:

  1. 5 eV (insulator)
  2. ≈ 1.1 eV
  3. 0 eV
  4. 12 eV
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Correct answer: B. ≈ 1.1 eV

Si band gap ≈ 1.1 eV. Ge: 0.7 eV. GaAs: 1.43 eV. Small enough that thermal energy can promote some electrons to conduction band at room temperature → semiconducting.

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In an intrinsic (pure) semiconductor at T > 0:

  1. Only electrons
  2. No charge carriers
  3. Only holes
  4. Equal number of electrons (in CB) and holes (in VB)
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Correct answer: D. Equal number of electrons (in CB) and holes (in VB)

Thermal excitation promotes electrons from valence band to conduction band, leaving holes. n_e = n_h = n_i (intrinsic carrier concentration). Both contribute to conductivity.

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