This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Schering Bridge”.
1. Schering bridge is one of the most widely used AC bridges.
Explanation: Schering bridge is an AC bridge used for the measurement of unknown capacitance, dielectric loss and power factor. It is one of the most commonly used AC bridges.
2. Schering bridge is used for _________
a) low voltages only
b) low and high voltages
c) high voltages only
d) intermediate voltages only
Explanation: Schering bridge is used for both low as well as high voltages. A particular bridge connection is used for low voltage. High voltages employ the use of a different type of Schering bridge.
3. Power factor of a Schering bridge is _________
a) p.f. = sin∅x = Zx⁄Rx
b) p.f. = cot∅x = Rx⁄Zx
c) p.f. = cos∅x = Rx⁄Zx
d) p.f. = tan∅x = Rx⁄Zx
Explanation: The power factor of the RC combination in a Schering bridge is given by the relation p.f. = cos∅x = Rx⁄Zx .
Rx is the series resistance
Zx is the series impedance comprising of Rx and Cx.
4. For phase angles close to 90°, the power factor of the bridge is _________
a) p.f. = ωRx
b) p.f. = ωCx
c) p.f. = Rx Cx
d) p.f. = ωRx Cx
Explanation: When phase angle reaches 90°, reactance equals the impedance and the power factor of the bridge is calculated using the relation,
5. For a series RC circuit, what is δ?
a) voltage between series RC combination and C
b) voltage between series RC combination
c) voltage across C
d) voltage across R
Explanation: In a series RC circuit, δ refers to the angle between the series combination of Rx, Cx and the voltage across the capacitance Cx. δ is also known as the loss angle.
6. What is the expression for the loss angle?
a) tan δ = ωR4
b) tan δ = ωR4 C4
c) tan δ = ωC4
d) tan δ = R4 C4
Explanation: The expression for the loss angle can be computed as the ratio of the tangent of the voltage drop across resistance Rx to the voltage drop across the capacitance Cx.
7. Quality factor is given by the expression
a) Q = 1⁄R
b) Q = R
c) Q = X⁄R
d) Q = XR
Explanation: The quality factor the Schering bridge circuit is defined as Q = X⁄R.
where, X = 1⁄wC is the capacitive impedance.
8. Dissipation factor is the reciprocal of quality factor.
Explanation: Dissipation factor for a circuit is defined as the reciprocal of the quality factor.
It is given by the expression Q = 1⁄wCR. It basically provides information about the quality of a capacitor.
9. Commercial Schering bridge can be used for the measurement of capacitances
a) from 10pF to 0.1nF
b) from 100pF to 1μF
c) from 50nF to 10mF
d) from 25mF to 5F
Explanation: Commercial Schering bridges are used for the measurement of capacitances in the range of a few pico farads to a few micro farads. Accuracy varies in the range of –2% to +2%.
10. A Schering bridge can be used for the
a) measuring voltages
b) measuring currents
c) testing capacitors
d) protecting the circuit from temperature rises
Explanation: A Schering bridge can be used with both low voltage as well as high voltages. A Schering bridge is basically used for the measurement of small capacitances at low voltages with high precision.
Sanfoundry Global Education & Learning Series – Electrical Measurements.
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