1. What is the relation between the balance equation and the magnitude of input voltage?
Directly proportional
Independent
Inversely proportional
Depends on the null indicator
Answer.1. Independent
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
From the above equation, the input voltage does not appear in the expression for the balanced equation. Thus balance equation is independent of the magnitude of input voltage.
2. The simplest type of bridge used for the measurement of medium resistances is known as ______
Kelvin
Schering
Anderson
Wheatstone
Answer.4. Wheatstone bridge
Explanation:-
The Wheatstone bridge circuit is used to compare an unknown resistance with a known resistance. The bridge is commonly used in control circuits. The wheat stone bridge is the most accurate method available for measuring resistance and is popular for laboratory use.
The resistance with values ranging from 1Ω to 100Ω is called medium resistance. The resistors employed in electronic circuits usually are of medium resistance type.
This bridge circuit is used to determine medium resistance ranging from approximately an ohm (1Ω) to low mega ohms (MΩ).
Wheatstone bridge is also used to measure the resistance of cables and telephone lines for the locatıon of fault positions. For measuring low resistances, care should be taken to reduce the error in measurement. Resistances of connecting leads and contacts introđuce some errors in measurement. Errors due to connecting leads and contacts can be eliminated when we use Kelvin double bridge.
The other different methods used for measurement of medium resistance are
Ammeter-Voltmeter method
Substitution method
Ohmmeter method
3. The measurement accuracy in a bridge circuit is
Low
Inaccurate
High
Medium
Answer.3. High
Explanation:-
Since the bridge circuit merely compares the value of an unknown component with that of an accurately known component (a standard), its measurement accuracy can be very high. This is because the readout of this comparison is based on the null indication at bridge balance, and is essentially independent of the characteristics of the null detector. The measurement accuracy is, therefore, directly related to the accuracy of the bridge component and not to that of the null detector used.
4. In control applications, one arm of the bridge circuit contains a _______
Capacitive element
Resistive element
Inductive element
Impedance element
Answer.2. Resistive element
Explanation:-
The bridge circuit can be used in the control circuits. When used in such control applications, one arm of the bridge contains a resistive element that is sensitive to the physical parameter like pressure, temperature, etc. which is to be controlled.
5. Accuracy of bridge circuit depends on _______
Component values
Null detector
Voltage source
Current source
Answer.1. Component Value
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.
6. Commonly used D.C. bridges are _______
Schering and Anderson
Maxwell inductance and capacitance
De Sauty’s and Wagner
Wheatstone and Kelvin
Answer.4. Wheatstone and Kelvin
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.
Schering Bridge is used for the measurement of Inductance.
De Sauty’s bridge & Schering Bridge is used for the measurement of Capacitacne.
7. The bridge circuit can be used in _______
High voltage circuits
Low power circuits
Control circuits
Digital integrated circuits
Answer.3. Control Circuits
Explanation:-
The bridge circuit can be used in the control circuits. When used in such control applications, one arm of the bridge contains a resistive element that is sensitive to the physical parameter like pressure, temperature, etc. which is to be controlled.
8. What happens to the balance condition, if the source and detector are interchanged?
Increases by a factor of 2
Reduces to half
Remains unchanged
Independent of the type of source and detector
Answer.4. Independent of the type of source and detector
Explanation:-
The bridge is balanced either manually or automatically using the output signal from the detector in a feedback loop to find the null position.
Under Balancing conditions, the unknown resistance Rx is given by
Rx = (R3R1)/R2
The null condition is independent of the source resistance, of the voltage source supplying the bridge, or the sensitivity or input resistance, of the detector. These, however, determine the precision with which the balance condition can be determined. Hence the balance condition is independent of the positions of the source and the detector.
9. What is the balanced condition for the given bridge?
Z1R3 = R2Z4
Z1R2 = R2Z3
Z1R4 = R2Z3
R3R2 = Z1Z4
Answer.1. Z1R3 = R2Z4
Explanation
The bridge is in a balanced condition when no current flows through the coil or the potential difference across the galvanometer is zero.
So at the balanced condition
VAC = VA − VC = 0
or
VA = VC
I1 = I2 & I3 = I4
V = V4 + V3 = V1 + V2
Applying Nodal voltage at A & B
Z4 × V/(Z4 + R3) = Z1 × V/(Z1 + R2)
Z1R3 = R2Z4
10. The advantages of the bridge circuits is/are
High Accuracy
Used in the control circuit
Balanced conditions remain unchanged
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.
