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Assertion (A): Routh criterion is in terms of array formulation which is more convenient to handle.Reason (R): This method is used to investigate the method of stability of higher order systems.

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Answer & Explanation
Correct AnswerB. Both (A) and (R) are true and (R) is not the correct explanation of (A)

Quick Explanation

Both statements are true: the Routh criterion converts a characteristic polynomial into an algebraic array and is especially convenient for determining the number of right-half-plane roots of higher-order systems without explicitly solving for all roots. However, the second statement is a use of the method rather than the precise reason the array formulation is convenient, so the final-key choice is B.

Formula / Key Relation

For characteristic polynomial:
an s^n + a_{n−1}s^{n−1}+...+a0=0
Number of first-column sign changes
= number of RHP roots.

Detailed Explanation

Concept & Reasoning

Routh-Hurwitz stability analysis uses polynomial coefficients to build the Routh table. Changes of sign in the first column equal the number of roots in the right-half s-plane. It scales well to higher-order characteristic equations compared with direct root calculation, while also handling special zero-row/zero-first-element cases with standard procedures.

How to Solve It in the Exam

Routh table → stability without solving all roots.

Important Exam Point

In assertion-reason questions, distinguish 'both true' from 'R explains A'.

Related Revision Path

This question sits in the revision path Control Systems → Stability → Routh-Hurwitz Criterion .

Routh Array explanatory diagram

Quick Trick

Routh table → stability without solving all roots.

Common Mistake

Assuming higher-order applicability alone logically explains why array handling is convenient.

Exam Tip

In assertion-reason questions, distinguish 'both true' from 'R explains A'.

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Previous Exam Appearances

Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207
Assistant Engineer (Electrical), Class-2, Road and Building Department2025Q. 207

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