Assertion–Reason: Rochelle salt and BaTiO3 as ferroelectrics Assertion (A): Rochelle salt and barium titanate are ferroelectric materials. Reason (R): Ferroelectric materials exhibit hysteresis in their polarization–electric field (P–E) characteristics.

Introduction / Context:
Ferroelectric materials possess a spontaneous polarization that can be reversed by an external electric field, producing a characteristic hysteresis loop. This item probes factual knowledge of examples and the correct role of hysteresis as a property, not a cause.

Given Data / Assumptions:

• Materials: Rochelle salt (sodium potassium tartrate) and barium titanate (BaTiO3).
• Room-temperature ferroelectricity (BaTiO3), and temperature-dependent phases (Rochelle salt).
• Standard P–E loop behaviour for ferroelectrics.

Concept / Approach:
Both materials are established ferroelectrics. Hysteresis is a signature behaviour of ferroelectrics, but it is a consequence of domain switching and energy barriers, not the underlying reason why a given crystal is ferroelectric. The microscopic cause lies in non-centrosymmetric structures enabling spontaneous polarization.

Step-by-Step Solution:
Validate A: Rochelle salt and BaTiO3 are ferroelectric → true.Validate R: Ferroelectrics exhibit P–E hysteresis → true.Causality check: R describes a property that results from ferroelectricity; it does not explain why those specific materials are ferroelectric → not a correct explanation.

Verification / Alternative check:
Phase transitions (Curie temperature) and crystal symmetry analysis confirm spontaneous polarization in these materials and their hysteresis loops under cycling fields.

Why Other Options Are Wrong:
(a) incorrectly treats a symptom (hysteresis) as the cause. (c) and (d) misstate truth values. (e) rejects well-known facts.

Common Pitfalls:

• Equating hysteresis presence with causation of ferroelectricity rather than a manifestation.

Final Answer:
Both A and R are true but R is not correct explanation of A