ECAT (Engineering College Admission) Physics: Electronics MCQs

Practice Electronics MCQs for ECAT (Engineering College Admission) Physics — topic-wise sets with solved answers.

ECAT (Engineering College Admission) Physics: Electronics MCQs — sample questions

  1. Question 1

    Q1. In a common emitter amplifier, the input resistance is 1 kΩ and load resistance is 3 kΩ. If β = 100, voltage gain is

    • A) 100
    • B) 200
    • C) 300
    • D) 400

    Answer: 300

    Explanation: Voltage gain = β * (R_load / R_input) = 100 * (3 / 1) = 300, using the formula for voltage gain in a common emitter amplifier.

  2. Question 2

    Q2. The energy band gap is maximum in

    • A) metals
    • B) superconductors
    • C) semiconductors
    • D) insulators

    Answer: insulators

    Explanation: Insulators have the largest energy band gap, typically > 3 eV, making it difficult for electrons to jump to the conduction band.

  3. Question 3

    Q3. The depletion layer in a p-n junction diode consists of

    • A) electrons
    • B) holes
    • C) immobile ions
    • D) both electrons and holes

    Answer: immobile ions

    Explanation: The depletion layer is formed by the immobile ions, which are the result of the diffusion of electrons and holes across the junction.

  4. Question 4

    Q4. In a p-type semiconductor, the acceptor level is 0.05 eV above the valence band. The maximum wavelength of light that can create a hole is

    • A) 2480 nm
    • B) 248 nm
    • C) 1240 nm
    • D) 620 nm

    Answer: 2480 nm

    Explanation: Using E = hc / λ, we get λ = hc / E = (6.626 * 10^-34 * 3 * 10^8) / (0.05 * 1.6 * 10^-19) = 2480 nm.

  5. Question 5

    Q5. The current gain of a transistor in common base configuration is 0.98. The current gain in common emitter configuration is

    • A) 49
    • B) 50
    • C) 98
    • D) 100

    Answer: 49

    Explanation: Using the formula β = α / (1 - α), we get β = 0.98 / (1 - 0.98) = 49.

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