# Electrical Measurements Questions and Answers – High Voltage Schering Bridge

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “High Voltage Schering Bridge”.

1. A Schering bridge can be used for capacitance measurements at low voltages.
a) True
b) False

Explanation: When a Schering bridge is used for the measurement of small capacitances at low voltages, it comprises of errors. In order to avoid this a high voltage Schering bridge is used.

2. How is the high voltage obtained?
a) by using a step up transformer
b) by using a high voltage source
c) by using a step down transformer
d) by using a high current source

Explanation: High voltage supply for a Schering bridge is obtained by making use of a step up transformer. The frequency for the high voltage supply used in a Schering bridge is 50 Hz.

3. The detector used in a high voltage Schering bridge is _________
a) tunable circuit
b) e.m.f source
c) vibration galvanometer

Explanation: A high voltage Schering bridge is used for the measurement of low capacitance values at high voltages. A vibration galvanometer is used as a detector in a high voltage Schering bridge.

4. Detector is very sensitive in a high voltage Schering bridge.
a) True
b) False

Explanation: In a high voltage Schering bridge the ratio arms have high impedance values. As a result, a very small current is drawn by the ratio arms. Hence the detector must be very sensitive in a high voltage Schering bridge.

5. How are the inter-capacitance errors minimized?
a) by separating the plates of the capacitance
b) by using earthing
c) by reducing the area of cross section of the capacitors
d) by increasing the distance between the capacitor plates

Explanation: In a high voltage Schering bridge, errors due to inter-capacitance between the high and low impedance ratio arms can be eliminated through earthing screens.
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6. How to minimize the effect of earth capacitance?
a) by increasing the supply voltage
b) by using a series resistance
c) by using a Wagner ground connection
d) by using an inductor across the circuit

Explanation: In a high voltage Schering bridge, the effect of earth capacitance on the circuit including the galvanometer and the contact leads is minimized by making use of a Wagner ground connection.

7. What is the effect of breakdown of high voltage capacitor?
a) No effect
b) voltage drop across the circuit reduces
c) circuit components rupture
d) a high voltage appears across the branches

Explanation: In a high voltage Schering bridge, a very high voltage appears across the branches when the breakdown of high voltage capacitor occurs. This is prevented by making use of a spark gap across the branches involved.

8. What is the dependence of frequency on the balance equation?
a) independent
b) varies by a factor of 2
c) depends on the supply magnitude
d) depends on the detector used

Explanation: In a high voltage Schering bridge, the balance equation does not depend on the frequency of operation of the circuit. A detector is only used for detecting the balance condition in a bridge circuit.

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