Assertion–Reason: De Sauty’s bridge is suitable only for measuring a pure (lossless) capacitor. Reason: Most practical capacitors are nearly perfect, so the loss can be ignored.

Introduction / Context:
De Sauty’s bridge is a classical AC bridge used to compare capacitances by balancing the ratio of two capacitors against the ratio of two resistors. Its usefulness depends on the assumption that the capacitors are ideal (lossless). Real-world capacitors exhibit dielectric loss, modeled by a series resistance or a loss tangent, which affects balance conditions.

Given Data / Assumptions:

• Assertion (A): The bridge is suitable only for pure capacitors.
• Reason (R): Practical capacitors are mostly perfect and loss can be ignored.
• Understanding of loss angle and dissipation factor is assumed.

Concept / Approach:
De Sauty’s bridge balance condition is C1/C2 = R4/R3. This relation holds strictly only if both capacitors are free from dielectric loss, because the bridge has no provision to balance out the resistive loss component. When dielectric loss is present, bridges like Schering bridge are used instead, as they include a loss arm to balance both capacitance and dissipation factor.

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