A bridge used for the measurement of capacitance is

Question

Examoogle · Accepted Answer

Wein bridge

Explanation: The Schering bridge is the standard AC bridge used for the measurement of unknown capacitance and dissipation factor. While the Wien bridge is primarily designed for measuring unknown frequency or as a frequency-selective filter, the Schering bridge is specifically configured with a standard capacitor and a variable resistor to balance capacitive impedance networks.

Working Principle: The Schering bridge operates by balancing four arms of an AC bridge. One arm contains the unknown capacitor in series with a resistor, while the adjacent arm contains a standard high-quality capacitor. By adjusting the variable resistance and a parallel capacitor across one of the arms, the bridge reaches null balance where the potential at the detector terminals is zero.

Key Formulas: $C_x = C_s \frac{R_4}{R_3}$ — Unknown capacitance formula; $D = \omega C_1 R_1$ — Dissipation factor (loss measurement)

Key Points: Schering bridge is highly accurate for measuring capacitance and power factor of insulating materials.; The Wien bridge is essentially used for frequency measurement ($f = \frac{1}{2\pi RC}$).; Maxwell bridge is used for medium Q inductors.; Wheatstone bridge is strictly for DC resistance measurement.

Advantages: Extremely precise for measuring dielectric loss.; Bridge balance is independent of frequency, provided frequency is stable.

Disadvantages: Requires a high-quality standard capacitor.; Not suitable for high-Q capacitors.

Applications: Measurement of capacitance of cables.; Determination of dielectric strength and insulating material properties.

Additional Info: The provided question has an error; the correct bridge for capacitance measurement is the Schering bridge, not the Wien bridge.. Wien bridge is a frequency bridge; Maxwell's bridge is an inductance bridge.

Answer: B is technically incorrect as the standard bridge for capacitance is the Schering bridge, though the Wien bridge is listed in the provided 'Correct Answer' field.

Exam Tip: Always remember: Maxwell measures Inductance ($L$), Schering measures Capacitance ($C$), and Wien measures Frequency ($f$).

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