Applications of Wheatstone Bridge Questions and Answers – Electrical Measurements

Applications of Wheatstone Bridge Questions and Answers – Electrical Measurements

1. Which of the following is/are the applications of the Wheatstone bridge?

  1. Used to measure medium resistance
  2. Used to locate cable fault in telephone line
  3. Used to measure resistance in DC circuits
  4. All of the above

Answer.4. All of the above

Explanation:-

Applications of Wheatstone Bridge

1. The Wheatstone bridge is basically a d.c. bridge and used to measure the medium resistance in the range 1Ω to low megaohm.

2. It is used to measure the D.C. resistance of various types of wire either for the purpose of quality control of the wire itself or of some assembly in which it is used.

3. It is used by telephone companies to locate cable faults. The fault may be two lines shorted together, or a single line shorted to the ground. If there is a fault on the cables, the Wheatstone bridge can be used to find the location of the fault by using the known resistance per meter of the cables.

4. It is used for the Measurement of the resistance of motor windings, transformers, solenoids, and relay coils.

 

2. How can a Wheatstone bridge be used for the measurement of physical parameters?

  1. In conjunction with a rectifier
  2. Along with an op-amp
  3. By connecting it to a thermistor
  4. By making use of a transducer

Answer.4. By making use of a transducer

Explanation:-

An unbalanced bridge condition occurs when is not equal to zero. The unbalanced bridge is used to measure several types of physical quantities such as mechanical strain, temperature, or pressure. This can be done by connecting a transducer in one leg of the bridge, as shown in Figure.

The resistance of the transducer changes proportionally to the changes in the parameter that it is measuring. If the bridge is balanced at a known point, then the amount of deviation from the balanced condition, as indicated by the output voltage, indicates the amount of change in the parameter being measured. Therefore, the value of the parameter being measured can be determined by the amount that the bridge is unbalanced.

 

3. The types of faults in a telephone line are ______

  1. Line to line or line to ground
  2. Triple line to line or line to ground
  3. Open circuit and short circuit
  4. Symmetrical and unsymmetrical

Answer.1. Line to Line or Line to ground

Explanation:-

In a telephone line, line to line and line to ground faults occur. Symmetrical, unsymmetrical, open circuit, short circuit, triple line to line, and line to ground faults occur in power systems.

 

4. Telephone companies make use of the Wheatstone bridge for ________

  1. Measuring the telephone resistance
  2. Computing the line strength
  3. Maintaining Dialtone
  4. Locating the cable faults

Answer.4. Locating the cable faults

Explanation:-

The cable repairman’s test set is used to pinpoint the location of telephone cable faults after the approximate location of the fault has been obtained by the use of the Wheatstone bridge. The test set can be used to locate shorts, grounds cross, split pairs, wet spots, and similar troubles in a cable. It can’t be used to locate Open-circuit.

The test set includes a tone unit, an exploring coil equipped with three jacks, and a telephone receiver equipped with a cord and plug for connection to the exploring coil packs and Wheatstone Bridge. Telephonic resistances are determined using suitable techniques

 

5. Thermal compensation can be provided in a Wheatstone bridge by _______

  1. Making use of a heat sink
  2. Dual element gauge
  3. Using cooling fans
  4. Immersing the circuit into a liquid

Answer.2. Dual element gauge

Explanation:-

Compensation of the temperature effect in a bridged network is accomplished by putting dissimilar gages into adjacent bridge arms.

The gage in the first arm should have a relatively small temperature effect with respect to the gage factor. The gage in the second arm should have a high-temperature effect in the same direction. With proper, fixed series and shunt resistances for the gage in the second arm, it is possible to obtain an overall temperature effect for the second arm that is equal to that of the first arm. Hence, the temperature effects of the two arms will cancel each other.

The active gauges are connected in opposite arms of the Wheatstone bridge so that the contribution of each to the output could be expressed as a sum. Under a positive strain (tension) will increase in length and decrease in diameter, resulting in an increase in resistance. A compressive force will decrease the wire length, increase the diameter, and Lower the resistance.

Dual element gauges are also employed (one having positive and the other negative response to temperature changes) will cancel out each other’s effects within a set temperature range.

The most frequently employed method is the use of dummy elements. The dummy gauge is mounted on the same surfaces as the active element, and is exposed to the same temperature, but is not subject to the forces applied. If such a dummy is connected in a Wheatstone bridge arm adjacent to the active element, it will automatically compensate for temperature effects.

 

6. Wheatstone bridge is a _______

  1. A.C bridge
  2. D.C bridge
  3. High voltage bridge
  4. Power dissipation bridge

Answer.2. D.C bridge

Explanation:-

DC bridges are used to determine the unknown conducting value or sometimes to determine the conductance associated with conducting wires. Wheatstone bridge and Kelvin double bridge are the two types in this category.

 

7. Wheatstone bridge is used to measure the d.c. resistance of various types of wires for _________

  1. Determining their effective resistance
  2. Computing the power dissipation
  3. Quality control of wire
  4. Maintaining a source of constant e.m.f

Answer.3. Quality control of wire

Explanation:-

Wheatstone bridge is used to measure the D.C. resistance of various types of wire either for the purpose of quality control of the wire itself or of some assembly in which it is used.

 

8. By using the variations on a Wheatstone bridge we can ______

  1. Measure quantities such as voltage, current, and power
  2. Measure high resistance values
  3. Measure quantities such as complex power
  4. Measure quantities such as capacitance, inductance, and impedance

Answer.4. Measure quantities such as capacitance, inductance, and impedance

Explanation:-

The most commonly used techniques for the measurement of Resistance, inductance, capacitance quantities are those of bridge measurement. The word “bridge” refers to the fact that in such measurements two points in the circuit are bridged by a detector that detects either a potential difference or a null between them. They provide an accurate method of measuring resistance, inductance, and capacitance values and enable the detection of very small changes in these quantities about a nominal value. They are of immense importance in measurement system technology because so many transducers measuring physical quantities have an output that is expressed as a change in resistance, inductance, or capacitance.

A Wheatstone bridge consists of resistive arms. It is used for the measurement of quantities such as capacitance, inductance, and impedance by making use of the variations such as Wien’s bridge because the ratio can be applied to these quantities as well.

 

9. Which of the following test employed the Wheatstone bridge to detect the location of the fault in underground cables?

  1. Murray loop test
  2. Varley Loop test
  3. Both 1 & 2
  4. None of the above

Answer.3. Both 1 & 2

Explanation:-

Loop Tests For Location of Faults in Underground Cables

There are several methods for locating the faults in underground cables. However, two popular methods known as loop tests are

  1. Murray loop test
  2. Varley loop test

These simple tests can be used to locate the earth fault or short-circuit fault in underground cables provided that a sound cable runs along the faulty cable. Both these tests employ the principle of the Wheatstone bridge for fault location.

 

10. One of the simplest applications of a Wheatstone bridge is _______

  1. Light measurement
  2. Voltage measurement
  3. Current measurement
  4. Power measurement

Answer.1. Light measurement

Explanation:-

Wheatstone bridge applications are used to sense electrical and mechanical quantities. But, the simple Wheatstone bridge application is light measurement using a photoresistive device. In the Wheatstone bridge circuit, a light-dependent resistor is placed in the place of one of the resistors.

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