13 Jun 2026

Electronics Exam Quiz

Five standard electronics MCQs for physics entrance practice.

electronics gate-2024 csir-net-2023 jest-2022

These are original exam-style practice questions based on common GATE, CSIR-NET and JEST electronics patterns.

Q: [GATE 2024 style] For an ideal operational amplifier with negative feedback, the input currents are
A: infinite
B: zero
C: equal to output current
D: equal to supply current
ANSWER: B
EXPLAIN: An ideal op-amp has infinite input impedance, so input currents vanish.
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Q: [CSIR-NET 2023 style] A forward-biased silicon diode has an approximate cut-in voltage of
A: $0.1\,\mathrm{V}$
B: $0.3\,\mathrm{V}$
C: $0.7\,\mathrm{V}$
D: $5\,\mathrm{V}$
ANSWER: C
EXPLAIN: Silicon p-n diodes typically conduct appreciably near $0.7\,\mathrm{V}$.
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Q: [JEST 2022 style] In a common-emitter amplifier, the output voltage is approximately
A: in phase with input
B: $180^\circ$ out of phase with input
C: always zero
D: independent of transistor bias
ANSWER: B
EXPLAIN: A common-emitter stage inverts the signal voltage.
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Q: [GATE 2021 style] The output of an ideal inverting op-amp amplifier is
A: $V_o=-(R_f/R_{in})V_i$
B: $V_o=(R_{in}/R_f)V_i$
C: $V_o=V_i$
D: $V_o=0$
ANSWER: A
EXPLAIN: Virtual ground analysis gives gain $-R_f/R_{in}$.
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Q: [CSIR-NET 2020 style] A NAND gate output is zero only when
A: both inputs are zero
B: one input is zero
C: both inputs are one
D: inputs are unequal
ANSWER: C
EXPLAIN: NAND is the negation of AND, so it is low only for input $1,1$.

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