Logic Hazards MCQs

Practice Logic Hazards MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Digital ElectronicsLogic Hazards

In a static-1 hazard, the output of a combinational circuit may momentarily do what even though it should remain at logic 1?

ARemain permanently LOW
BDrop briefly to logic 0
COscillate indefinitely
DBecome high-impedance

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Correct Answer: B. Drop briefly to logic 0

Explanation: A static-1 hazard is an unwanted 1→0→1 glitch caused by unequal propagation delays along different logic paths.

Reference: Standard digital electronics: static hazards

Question 2

Digital ElectronicsLogic Hazards

For the SOP function F = AB + A̅C, which consensus term can be added to eliminate the potential static-1 hazard between the two product terms?

AAC
BBC
CA̅B
DABC

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Correct Answer: B. BC

Explanation: By the consensus theorem, the consensus of AB and A̅C is BC. Adding BC provides overlapping coverage and can eliminate the static-1 hazard.

Reference: Standard digital electronics: consensus theorem and hazards

Question 3

Digital ElectronicsLogic Hazards

A dynamic hazard is characterized by an output that should change once but instead?

AChanges multiple times before settling
BNever changes under any condition
CBecomes permanently high impedance
DAlways changes exactly once

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Correct Answer: A. Changes multiple times before settling

Explanation: A dynamic hazard occurs when unequal delays through multiple paths cause several output transitions before the circuit reaches its final correct value.

Reference: Standard digital electronics: dynamic hazards

Question 4

Digital ElectronicsLogic Hazards

A static-0 hazard in a POS combinational circuit is an unwanted transition in which the output, ideally remaining 0, may briefly?

ARise to 1 and return to 0
BRemain permanently at 1
CEnter high impedance
DToggle only on a clock edge

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Correct Answer: A. Rise to 1 and return to 0

Explanation: A static-0 hazard is a temporary 0→1→0 glitch caused by unequal propagation delays when the correct steady output should remain LOW.

Reference: Standard digital electronics: static-0 hazards