Introduction of Bridge Circuit Question and Answers – Electrical Measurements

 1. Which of the following components are measured by bridge circuit?

  1. Diode, triode, and thyristor
  2. Resistance, capacitance, and inductance
  3. Transistor, thermistor, and antenna
  4. LED, op-amp, and transducer

Answer.2. Resistance, capacitance, and inductance

Explanation:-

The bridges are not only used for the measurement of resistance but also used for the measurement of various component values like inductance or capacitance etc.

We can say that the bridges are the best and most used methods for the precise measurement of resistance, inductance, and capacitance, Since it is generally more difficult to obtain accuracy with deflection methods.

 

2. The bridge circuit is based on the principle of

  1. Null Detector
  2. Full Detector
  3. Current Detector
  4. Voltage Detector

Answer.1. Null Detector

Explanation:-

The bridge circuit uses the comparison measurement method and operates on the null-indication principle. A null detector identifies when a given value is zero.

The bridge circuit compares the value of an unknown component with that of an accurately known standard component. Thus the accuracy depends on the bridge components and not on the null indicator.

The bridge is said to be balanced when there is no current through the galvanometer or when the potential difference across the galvanometer is zero.

 

3. Which of the following instrument is used as a Null detector for the bridge circuit

  1. Potentiometer
  2. Transduced
  3. Galvanometer
  4. Inductor

Answer.3. Galvanometer

Explanation:-

A galvanometer is used in a bridge circuit as a null detector underbalanced conditions. When an unknown voltage is compared with a known voltage and a galvanometer is connected in the circuit, when the two voltages are equal, no current will flow through the galvanometer.

Underbalanced conditions the galvanometer will provide zero reading. Its pointer will stay in its center position marked zero.

A potentiometer is an instrument that is basically used for accurate measurement of an unknown emf of low value by comparing it with a known standard emf. The accuracy of the measurement depends on how accurately the value of the known voltage source is known to us.

 

4. A simple bridge circuit consists of a network of ______

  1. 3 resistance arms
  2. 2 resistance arms
  3. 4 resistance arms
  4. 6 resistance arms

Answer.3. 4 Resistance arms

Explanation:-

A bridge circuit in its simplest form consists of a network of four resistance arms forming a closed circuit. A source of current is applied to two opposite junctions. The current detector is connected to the other two junctions as shown in Fig.

The arm consisting of the resistance R1 and R2 are called ratio arms.

The arm consisting of the standard known resistance R3 is called the standard arm and the resistance Rx is the unknown resistance to be measured. The battery is connected between a and c while the galvanometer (current detector) is connected between b and d.

 

5. D.C. bridges are used for  the _______

  1. Measurement of resistance
  2. Measurement of capacitance
  3. Measurement of current
  4. Measurement of inductance

Answer.1. Measurement of resistance

Explanation:-

There are two types of bridges, namely the DC bridges and AC bridges. The DC bridges are used for the measurement of resistance they use the D.C. voltage as the excitation voltage.

AC bridges are used for the measurement of inductance and capacitance it used alternate voltage as excitation voltage.

 

6. A.C bridge is used for the measurement of

  1. Resistance
  2. Inductance
  3. Capacitance
  4. All of the above

Answer.4. All of the above

Explanation:-

AC bridges can also be used for resistance measurements, but they are used to determine inductance, capacitance, impedance, admittance, or the frequency of the AC input.

 

7.  Which of the following is/are D.C bridges

  1. Maxwell Bridge & Hay Bridge
  2. Kelvin Bridge & Wheat Stone Bridge
  3. Schering Bridge & Hay’s Bridge
  4. Heaviside Bridge & Carey Foster Bridge

Answer.2. Kelvin Bridge & Wheat Stone 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.

 

8. Relationship at balance condition between the component values of the four arms of a bridge is known as _________

  1. Full load condition
  2. Open circuit condition
  3. Short circuit condition
  4. Balancing condition

Answer.4. Balancing Condition

Explanation:-

The bridge is in a balanced condition when no current flows through the coil or the potential difference across the galvanometer is zero.

Under Balancing conditions, the unknown resistance Rx is given by

Rx = (R3R1)/R2

 

9. Which method is used by the bridge circuit

  1. Absolute
  2. Relative
  3. Differential
  4. Comparison

Answer.4. Comparison Method

Explanation:-

The bridge circuit operates on the null detection principle and uses the principle of comparison measurement methods. It compares the value of an unknown component with that of an accurately known standard component. Thus, the accuracy of the measurement depends on the bridge and not on the null detector.

 

10. The accuracy of a bridge depends on the _______

  1. Null indicator
  2. Bridge components
  3. Current source
  4. Voltage source

Answer.2. Bridge Component

Explanation:-

Bridge compares the value of an unknown component with that of an accurately known standard component. Thus, the accuracy of the measurement depends on the bridge and not on the null detector.

 

11. The bridge circuit is called balanced when?

  1. Voltage is applied to the circuit
  2. Current flows through the opposite ends of the bridge circuit
  3. No current flows through the galvanometer
  4. Impedance is minimum

Answer.2. Current flows through the opposite ends of the bridge circuit

Explanation

The bridge circuit operates on the null detection principle and uses the principle of comparison measurement methods. It compares the value of an unknown component with that of an accurately known standard component. Thus, the accuracy of the measurement depends on the bridge and not on the null detector. When no current flows through the null detector, the bridge is said to be balanced.

Under Balancing conditions, the unknown resistance Rx is given by

Rx = (R3R1)/R2

 

12. The advantages of the bridge circuits is/are

  1. High Accuracy
  2. Used in the control circuit
  3. Balanced conditions remain unchanged
  4. All of the above

Answer.4. All of the above

Explanation:-

Advantages of Bridge Circuit

The various advantages of the bridge circuit are as follows:

1. The measurement accuracy is high because the measurement is done by comparing the unknown value with the standard value.

2. The accuracy is not dependent on the characteristic of a null detector and is dependent on the component value.

3. The balanced equation is independent of the magnitude of the input voltage. These quantities do not appear in the balanced equation expression.

4. The balance condition remains unchanged if the source and detector are interchanged.

5. The balanced equation is independent of the sensitivity of the null detector.

6. The bridge circuit can be used in the control circuit.

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