A standard capacitor is preferred to a standard inductor in precise bridge work because it
Answer: C
A capacitor's field is contained between its plates, so it neither couples to its surroundings nor suffers eddy current and hysteresis loss in nearby metal. An inductor radiates a field, picks up stray flux and changes value with what lies near it.
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Hay's bridge is preferred to the Maxwell-Wien bridge for coils of
Answer: D
In Hay's bridge the capacitor has a resistance in series rather than in parallel with it, and the resistance needed comes out inversely proportional to Q. For a high-Q coil the Maxwell-Wien bridge would call for an impracticably large parallel resistance, whereas Hay's needs only a small one.
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In Hay's bridge the resistance is connected
Answer: A
That series connection is the single structural difference from the Maxwell-Wien bridge, and it reverses which coils the bridge suits. The balance equations of Hay's bridge contain a Q-dependent term, so the inductance found is exact only if Q is large.
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Anderson's bridge is a modification of the Maxwell-Wien bridge in which
Answer: B
A fifth arm carrying a variable resistance is added to a bridge using a fixed capacitor, and the network becomes a five-arm one whose balance is worked out by delta-star conversion. Its merit is that a fixed standard capacitor suffices and low-Q coils are handled well.
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The chief practical drawback of Anderson's bridge is that
Answer: C
The extra branch makes the two balance conditions interdependent, so a change made for one disturbs the other and convergence is slow. Set against that, only a fixed capacitor is needed and low-Q coils are measured accurately, which is why the bridge survives.
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Owen's bridge measures inductance in terms of
Answer: D
Its distinction is that one balance condition is set by a resistance and the other by a capacitance, and the two do not interact. That independence makes it quick to use over a wide range of inductance, at the cost of needing two capacitors, one of them variable.
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Which bridge would be chosen to measure the inductance of a coil whose quality factor is about 0.5?
Answer: A
A quality factor below one is a very lossy coil. Hay's bridge is ruled out because its inductance expression is only approximate at low Q, and the Maxwell-Wien bridge would need an unmanageably large parallel resistance. Anderson's bridge handles such coils well.
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De Sauty's bridge in its simple form compares
Answer: B
Two arms hold the unknown and standard capacitors and the other two are resistances, so the ratio of the capacitances comes out as the inverse ratio of the resistances. It is the simplest of the alternating bridges and the direct analogue of the Wheatstone form.
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The simple form of De Sauty's bridge can be balanced properly only if both capacitors are
Answer: C
A real capacitor has loss, which gives it a phase angle short of ninety degrees. If the two capacitors differ in loss, the angle condition cannot be met and the detector never falls fully silent. The modified bridge adds a resistance in series with each capacitor to cure exactly this.
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The modification introduced by Grover into De Sauty's bridge is the addition of
Answer: D
Each capacitive arm becomes a capacitor with a series resistance, and adjusting those resistances satisfies the phase condition as well as the magnitude one. The bridge then also yields the difference in the loss angles of the two capacitors.
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