Bridges Basics - Electrical Measurements Quest...

about:reader?url=https://www.sanfoundry.com/...

sanfoundry.com

Bridges Basics - Electrical Measurements Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Introduction of Bridges”. 1. A bridge circuit is used for the measurement of the following components: a) Resistance, capacitance and inductance b) Diode, triode and thyristor c) Transistor, thermistor and antenna d) LED, op amp and transducer View Answer Answer: a Explanation: A bridge circuit is basically used for the measurement of basic electronic components such as resistance, capacitance and inductance. 2. A simple bridge circuit consists of a network of __________ a) 3 resistance arms 1 of 5

3/19/18, 01:55



b) 2 resistance arms c) 4 resistance arms d) 6 resistance arms View Answer Answer: c Explanation: A simple bridge circuit is made of a network consisting of 4 resistance arms. Usually a galvanometer is connected between the ends of the opposite two junctions in order to measure the flow of current. 3. What is applied to the two opposite junctions of a bridge circuit. a) source of voltage b) source of current c) source of power d) source of impedance View Answer Answer: b Explanation: A current source is connected between the two opposite junctions of a bridge circuit. Deflection of the galvanometer in the circuit indicates the flow of current. 4. A bridge circuit uses which method of measurement ? a) absolute b) relative c) differential d) comparison View Answer Answer: d Explanation: A bridge circuit makes use of comparison 2 of 5

3/19/18, 01:55



measurement method.In this method the bridge compares the value of an unknown component with a standard value of a given component. 5. The principle on which a bridge circuit operates is a) null indication b) ampere’s rule c) partial indication d) kirchhoff’s laws View Answer Answer: a Explanation: A bridge circuit operates on the principle of null indication. Based on the deflection of the galvanometer, current flows between the two opposite junctions. 6. The accuracy of a bridge depends on the _________ a) null indicator b) bridge components c) current source d) voltage source View Answer Answer: b Explanation: As a bridge circuit compares the value of an unknown component with the value of a standard, it’s accuracy depends on the bridge components. 7. When is the bridge circuit balanced ? a) When voltage is applied b) When current flows through the opposite ends of the bridge circuit c) When no current flows through the galvanometer 3 of 5

3/19/18, 01:55



d) When impedance is minimum View Answer Answer: c Explanation: The bridge circuit is said to be balanced when no current flows through the null indicator which is generally a galvanometer. 8. Relationship at balance condition between the component values of the four arms of a bridge is known as a) full load condition b) open circuit condition c) short circuit condition d) balancing condition View Answer Answer: d Explanation: During balance condition or equilibrium there exists a certain relationship between the component values of the four arms of the bridge. This relationship is known as the balancing condition or balancing equation. 9. D.C. bridges are used for _________ a) measurement of resistance b) measurement of capacitance c) measurement of current d) measurement of inductance View Answer Answer: a Explanation: Resistance measurements are done by making use of a suitable D.C. bridge.

4 of 5

3/19/18, 01:55



10. What is used to characterise single port devices, multiport devices etc? a) current values b) impedance values c) voltage values d) power values View Answer Answer: b Explanation: Impedance values are used to characterize one port devices, networks, multiport devices and other systems. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:55

Bridge Circuits Advantages - Electrical Measur...


sanfoundry.com

Bridge Circuits Advantages Electrical Measurements Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Advantages of Bridge Circuits”. 1. What is the relation between the balance equation and the magnitude of input voltage? a) directly proportional b) independent c) inversely proportional d) depends on the null indicator View Answer Answer: b Explanation: The input voltage does not appear in the expression for the balance equation. Thus balance equation is independent of the magnitude of input voltage. 2. Accuracy of bridge circuit depends on _________ a) component values b) null detector 1 of 5

3/19/18, 01:55



c) voltage source d) current source View Answer Answer: a Explanation: The accuracy of measurement of a bridge circuit depends on the values of the components used in it. Voltage source supplies dc bias to the circuit while the detector is used for balance condition. 3. What happens to the balance condition, if the source and detector are interchanged? a) increases by a factor of 2 b) reduces to half c) remains unchanged d) independent of the type of source and detector View Answer Answer: c Explanation: The balance condition is independent of the positions of the source and the detector. Source and detector can be connected across any two sets of opposite arms of the bridge. 4. The simplest type of bridge used for the measurement of medium resistances is known as a) Kelvin b) Schering c) Anderson d) Wheatstone View Answer Answer: d 2 of 5

3/19/18, 01:55



Explanation: Wheatstone bridge is the simplest bridge that is used for the measurement of medium resistances. Kelvin bridge is used for the measurement of low resistance, whereas Schering bridge is used for the measurement of high voltages. 5. How is the measurement accuracy in a bridge circuit? a) high b) low c) medium d) inaccurate View Answer Answer: a Explanation: The measurement is done by comparing the unknown value with a standard known value. Thus the measurement accuracy is high in a bridge circuit. 6. The bridge circuit can be used in _________ a) high voltage circuits b) low power circuits c) control circuits d) digital integrated circuits View Answer Answer: c Explanation: The bridge circuit is generally used in control applications. Control systems make use of bridge circuits for industrial applications. 7. Commonly used D.C. bridges are _________ a) Schering and Anderson b) Maxwell inductance and capacitance 3 of 5

3/19/18, 01:55



c) DeSauty and Wagner d) Wheatstone and Kelvin View Answer Answer: d Explanation: Wheatstone and Kelvin are the commonly used bridges for the measurement of resistance. Wagner’s and De Sauty’s bridges are used for shielding the circuit. 8. In control applications, one arm of the bridge circuit contains a _________ a) capacitive element b) resistive element c) inductive element d) impedance element View Answer Answer: b Explanation: One of the arms of a bridge circuit in general consists of a resistive element. Control systems employ resistive elements for industrial applications. 9. What are the physical parameters that are to be controlled when a bridge is used in control applications? a) area and volume b) mass and weight c) pressure and temperature d) current and voltage View Answer Answer: c Explanation: In control applications, when one of the arms of the bridge circuit consists of a resistance element, 4 of 5

3/19/18, 01:55



sensitive physical parameters such as pressure and temperature are to be controlled. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:55

Wheatstone Bridge Balance Condition Question...


sanfoundry.com

Wheatstone Bridge Balance Condition Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Wheatstone Bridge Balance Condition”. 1. Wheatstone bridge consists of _________ a) 4 resistive arms b) 2 resistive arms c) 6 resistive arms d) 8 resistive arms View Answer Answer: a Explanation: A Wheatstone bridge essentially consists of 4 resistive arms. The arms are such that two resistances appear across each end. 2. A galvanometer is used as a _________ a) current source b) voltage source c) null detector d) input impedance

1 of 5

3/19/18, 01:55



View Answer Answer: c Explanation: A galvanometer is used as a null detector to detect the flow of current across the ends of the two opposite junctions of the circuit. Voltage source is used for providing the required dc supply to the bridge. 3. The opposite two ends of a Wheatstone bridge consist of _________ a) voltage and current source b) e.m.f and null detector c) resistance and capacitance d) inductance and impedance View Answer Answer: b Explanation: The two opposite ends of a Wheatstone bridge circuit consists of a source of e.m.f and a null detector. Four arms of a Wheatstone bridge consist of resistances. Inductance and capacitance do not appear in a Wheatstone bridge. 4. The arms consisting of the resistances R1 and R2 are called _________ a) resistance arms b) impedance arms c) source arms d) ratio arms View Answer Answer: d Explanation: The arms consisting of the two resistances R1 2 of 5

3/19/18, 01:55



and R2 are known as the resistance arms. Sources do not appear on the arms of the bridge and they are connected across opposite ends. Wheatstone bridge is purely resistive in nature. 5. The arm consisting of the standard known resistance R3 is known as __________ a) standard arm b) resistance arm c) accurate arm d) known arm View Answer Answer: a Explanation: The arm consisting of the standard known resistance R3 is known as the standard arm. By making use of this resistance value the unknown resistance can be determined using the balance condition. 6. Resistance R4 is known as ________ a) standard resistance b) unknown resistance to be measured c) resistance arm d) input resistance View Answer Answer: b Explanation: R4 is the unknown resistance whose value has to be found by comparison with a standard. R3 is known as the standard resistance. Resistance arm comprises of four resistances including R1, R2, R3, and R4. 7. What is connected between the two ends of a 3 of 5

3/19/18, 01:55



Wheatstone bridge? a) current and voltage source b) ammeter and voltmeter c) battery and galvanometer d) ohmmeter and wattmeter View Answer Answer: c Explanation: A battery is connected between the two ends of the Wheatstone bridge while a galvanometer is connected between the opposite two ends of the circuit. Ammeter is connected in series with the circuit. 8. Wheatstone bridge works on the principle of ________ a) full deflection b) partial deflection c) no deflection d) null deflection View Answer Answer: d Explanation: The Wheatstone bridge works on the principle of null deflection. A galvanometer is usually used for measuring the flow of current in the bridge circuit. 9. The balance condition of a Wheatstone bridge depends on the a) ratio of arms R1 and R1 b) ratio of arms R3 and R4 c) emf source and null detector d) current source and power source View Answer 4 of 5

3/19/18, 01:55



Answer: a Explanation: The ratio of the arms R1 and R2 determines the balance condition of a Wheatstone bridge. The balance condition is given by the equation R4 = R3R1⁄R2. 10. Balance condition can be obtained by a) varying the standard resistance R3 b) varying the resistance arms R1 and R2 c) keeping the unknown resistance R4 constant d) by making use of a null detector View Answer Answer: b Explanation: The balance condition in a Wheatstone bridge can be obtained by varying the resistances R1 and R2. Null detector is used for determining balance condition. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:55

Wheatstone Bridge Sensitivity Questions and A...


sanfoundry.com

Wheatstone Bridge Sensitivity Questions and Answers by Manish 3-4 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Sensitivity of Wheatstone Bridge”. 1. When bridge is balanced, what is the current flowing through the galvanometer? a) 0 b) depends on the ratio arms R1 and R2 c) varies by a factor of 2 d) depends on the type of null detector used View Answer Answer: a Explanation: Under bridge balance condition, no current flows through the galvanometer. Current flow is independent of the values of ratio arms R1 and R2. 2. Amount of deflection of the galvanometer depends on _________ a) resistance of the ratio arms b) sensitivity

1 of 5

3/19/18, 01:56



c) current flowing through the bridge d) emf across the circuit View Answer Answer: b Explanation: The amount of deflection of the galvanometer depends upon its sensitivity. Resistance of the ratio arms does not affect the amount of deflection of the galvanometer. 3. Sensitivity is defined as _________ a) amount of voltage per unit current b) amount of power per unit voltage c) amount of resistance per unit voltage d) amount of deflection per unit current View Answer Answer: d Explanation: Sensitivity is expressed as Thus sensitivity is defined as the amount of deflection per unit current. 4. Sensitivity is expressed in a) cm/A b) m/mA c) mm/µA d) inch/nA View Answer Answer: c Explanation: where, deflection is in mm and current is in µA. So the unit of sensitivity is mm/ µA.

2 of 5

3/19/18, 01:56



5. What is the relation between the sensitivity and deflection for a galvanometer? a) directly proportional b) inversely proportional c) independant of each other d) depends on the type of galvanometer used View Answer Answer: a Explanation: Thus we see that sensitivity is directly proportional to the deflection. 6. The voltage sensitivity of a galvanometer is given by _________ a) Sv = e⁄θ b) Sv = θ⁄e c) Sv = 1⁄e

d) Sv = 1⁄θ View Answer Answer: b Explanation: Voltage sensitivity is defined as the amount of deflection per unit voltage and is given by the relation Sv = θ⁄e. 7. Unit of voltage sensitivity is _________ a) volts per degrees b) amps per ohms c) degrees per volts d) watts per amps View Answer 3 of 5

3/19/18, 01:56



Answer: c Explanation: So the unit of voltage sensitivity is degrees per volts as deflection is measured in degrees and voltage is in volts. 8. Bridge sensitivity is defined as

View Answer Answer: d Explanation: The bridge sensitivity is defined as the amount of deflection of the galvanometer per unit fractional change in the unknown resistance. Here ΔR/R denotes the fractional change in the unknown resistance. 9. Maximum sensitivity occurs when a) R3 ⁄ R4 = 1 b) R2 ⁄ R4 = 1 c) R1 ⁄ R2 = 1

d) R3 ⁄ R2 = 1 View Answer Answer: a Explanation: Under a small unbalance condition, the bridge sensitivity equation becomes Here E is the emf of the circuit. For

4 of 5

3/19/18, 01:56



maximum bridge sensitivity, we get R3=R4. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:56

Electrical Measurements Assessment Questions ...


sanfoundry.com

Electrical Measurements Assessment Questions Sanfoundry by Manish 4-5 minutes

This set of Electrical Measurements Assessment Questions and Answers focuses on “Measurement Errors in a Wheatstone Bridge”. 1. The Wheatstone bridge is used for the measurement of _________ a) 1ῼ to a few megaohms b) 1kῼ to a few megaohms c) 1Mῼ to a few gigaohms d) 1mῼ to a few ohms View Answer Answer: a Explanation: A Wheatstone bridge is used for the measurement of medium resistance in the range of 1ῼ to a few megaohms. Kelvin bridge is used for the measurement of low resistance. 2. The source of error in a Wheatstone bridge is due to _________ 1 of 5

3/19/18, 01:56



a) range of galvanometer used b) type of the source of emf used c) limiting errors of the three known resistances d) balance condition View Answer Answer: c Explanation: The main source of error in a Wheatstone bridge is because of the limiting errors of the three known resistances. As a result very precise resistances are required with 1 % tolerance. 3. What is the main source of error in a null detector? a) lower current detection ability b) insufficient sensitivity of the null detector c) wiring resistance d) power dissipation View Answer Answer: b Explanation: Resistance of wires and power dissipation are some of the causes for error in a null detector. But insufficient sensitivity is the major source of error in a null detector such as a galvanometer. 4. When current es through the resistances in the Wheatstone bridge what happens? a) voltage drop occurs b) null detector burns c) back emf is induced d) temperature increases due to power dissipation View Answer 2 of 5

3/19/18, 01:56



Answer: d Explanation: Current flow through the resistances causes power dissipation i.e. I2R leading to an increase in the temperature. As the bridge consists of pure resistances, there is no back e.m.f induced. 5. What is the effect of the increase in temperature on the resistance elements? a) directly proportional b) independant c) inversely proportional d) changes by a factor of 10 View Answer Answer: a Explanation: Temperature affects resistance of the circuit. Resistance has a positive temperature coefficient and increases linearly with rise in temperature. 6. Heating effect in the Wheatstone bridge can be avoided by _________ a) using an expensive emf source b) limiting current to a safe value c) using heating sinks d) immersing the setup in ice View Answer Answer: b Explanation: Heating effect can be eliminated by limiting the current through the circuit to a safe value and by calculating the power dissipation in the arms. Heat sinks are typically used in power electronic applications. 3 of 5

3/19/18, 01:56



7. The main error when measuring low resistances is _________ a) power dissipation of the arms b) voltage drop across the emf source c) lead and resistance d) current flowing through the circuit View Answer Answer: c Explanation: Voltage drop across the circuit along with power dissipation lead to errors in the measurement of low resistances. The resistance of leads and s of the external circuit adds to the values in the circuit. This is the main source of error while measuring low resistances. 8. How is thermal emf generated? a) when current flows b) when voltage is applied c) when the null detector is connected d) when dissimilar metals come in View Answer Answer: d Explanation: When dissimilar metals come into with each other in a galvanometer circuit, thermal emf is generated. Null detector is used for detecting the balance condition. 9. Thermal emf can be prevented by _________ a) using more sensitive galvanometers b) using similar metals c) by separating the dissimilar metals 4 of 5

3/19/18, 01:56



d) reducing the supply emf View Answer Answer: a Explanation: Thermal emf can be eliminated by making use of sensitive galvanometers consisting of copper coils and copper suspension systems. Dissimilar metals can’t be physically separated. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements Assessment Questions, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:56

Wheatstone Bridge Applications Questions and ...


sanfoundry.com

Wheatstone Bridge Applications Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Applications of Wheatstone Bridge”. 1. Wheatstone bridge is a __________ a) a.c. bridge b) d.c. bridge c) high voltage bridge d) power dissipation bridge View Answer Answer: b Explanation: The Wheatstone bridge is a d.c. bridge that is used for the measurement of medium resistance. Schering bridge is used for measurement of high voltages. AC bridges comprise of Anderson bridge, Maxwell Bridge etc. 2. Wheatstone bridge is used to measure resistance in the range of ________ a) 1Ω to a few megaohms b) 10kΩ to a few megaohms

1 of 5

3/19/18, 01:56



c) 100MΩ to a few gegaohms d) 100Ω to a few teraohms View Answer Answer: a Explanation: Wheatstone bridge is the simplest form of bridge circuit. It is basically used for the measurement of medium resistances in the range of 1Ω to a few megaohms. 3. Wheatstone bridge is used to measure the d.c. resistance of various types of wires for a) determining their effective resistance b) computing the power dissipation c) quality control of wire d) maintaining a source of constant e.m.f View Answer Answer: c Explanation: Wheatstone bridge is used to measure the d.c. resistance of various types of wires for controlling the quality of the wires. Voltage source maintains a constant e.m.f in the bridge circuit. 4. Telephone companies make use of the Wheatstone bridge for _________ a) measuring the telephone resistance b) computing the line strength c) maintaining dialtone d) locating the cable faults View Answer Answer: d Explanation: Cable faults in telephones can be located by 2 of 5

3/19/18, 01:56



telephone companies by making use of a Wheatstone bridge. Telephonic resistances are determined using suitable techniques. Dialtone is maintained through optical fibre technology. 5. The types of faults in a telephone line are ________ a) line to line or line to ground b) triple line to line or line to ground c) open circuit and short circuit d) symmetrical and unsymmetrical View Answer Answer: a 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. 6. How can a Wheatstone bridge be used for the measurement of physical parameters? a) in conjunction with a rectifier b) along with an op amp c) by connecting it to a thermistor d) by making use of a transducer View Answer Answer: b Explanation: A Wheatstone bridge can be used for the measurement of physical parameters such as temperature, strain, light, etc by making use of an operational amplifier. Rectifier circuits are used for conversion of ac to dc. 7. By using the variations on a Wheatstone bridge we can 3 of 5

3/19/18, 01:56



a) measure quantities such as voltage, current and power b) measure high resistance values c) measure quantities such as complex power d) measure quantities such as capacitance, inductance and impedance View Answer Answer: d Explanation: In its simplest form a Whetstone bridge consists of resistive arms. A Wheatstone bridge is used for the measurement of quantities such as capacitance, inductance and impedance by making use of the variations. 8. One of the simplest applications of a Wheatstone bridge is ________ a) voltage measurement b) current measurement c) light measurement d) power measurement View Answer Answer: c Explanation: Wheatstone bridge consists of simple resistances in the ratio arms. One of the simplest applications of a Wheatstone bridge is the measurement of light by making use of a photoresistive device. 9. Thermal compensation can be provided in a Wheatstone bridge by ________ a) using more than one resistive sensor b) making use of a heat sink c) using cooling fans 4 of 5

3/19/18, 01:56



d) immersing the circuit into a liquid View Answer Answer: a Explanation: By making use of more than one resistive sensor within the four arms of a Wheatstone bridge we get a full bridge, half bridge or a quarter bridge setup with automatic balancing effect. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:56

Wheatstone Bridge Limitations Questions and ...


sanfoundry.com

Wheatstone Bridge Limitations Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Limitations of Wheatstone Bridge”. 1. Wheatstone bridge can’t be used for measurement of a) high resistance b) medium resistance c) low resistance d) accurate resistance View Answer Answer: a Explanation: Wheatstone bridge can be used for the measurement of medium resistances only. Kelvin bridge is used for the measurement of medium resistances. 2. Cost of maintenance of Wheatstone bridge is _________ a) low b) high c) depends on the components d) depends on the source e.m.f

1 of 5

3/19/18, 01:56



View Answer Answer: b Explanation: As the resistance must have a tolerance of upto 1%, cost of maintenance of the Wheatstone bridge circuit is expensive. Voltage source does not add to the cost of maintenance of a Wheatstone bridge as it is uniform for all bridge circuits. 3. What is the effect of galvanometer on measurement of high resistance? a) no effect b) depends on the e.m.f source c) galvanometer becomes insensitive to imbalance d) depends on the type of galvanometer used View Answer Answer: c Explanation: If the Wheatstone bridge is used for the measurement of high resistance, the galvanometer becomes insensitive and does not detect any imbalance. 4. What is the effect of heat on the resistances in a Wheatstone bridge? a) no effect b) increases the voltage drop across the circuit c) decreases the current flowing through the circuit d) causes a permanent change in the resistance values View Answer Answer: d Explanation: As the current flowing through the Wheatstone bridge circuit increases, the temperature of the resistance 2 of 5

3/19/18, 01:56



increases. As a result the resistance values are changed permanently. 5. Effect of high dc on Wheatstone bridge. a) no effect b) not susceptible c) burns the circuit d) increases the temperature View Answer Answer: b Explanation: A Wheatstone bridge is not susceptible to the flow of high dc current. A Wheatstone bridge in simplest form is used for the measurement of resistance with values in the medium resistance range. 6. A Wheatstone bridge may not give accurate readings if _________ a) it is not balanced b) it is balanced c) the voltage drop across the circuit is maximum d) excessive current flows through the circuit View Answer Answer: a Explanation: A Wheatstone bridge circuit may give inaccurate measurement of resistance if it is not balanced properly. Current flow through a Wheatstone bridge circuit is fixed as the e.m.f source magnitude is constant. 7. What is the effect of lead wires on the Wheatstone bridge? a) no effect 3 of 5

3/19/18, 01:56



b) stabilizes the system c) desensitizes the system d) increases the resistance of the circuit View Answer Answer: c Explanation: The lead wires connecting the resistance arms of a Wheatstone bridge add to the existing values of resistances across the ratio arms. As a result the net value of resistance changes, thus destabilizing the system. 8. Why a Wheatstone bridge can’t be used for signal conditioning? a) due to the galvanometer b) due to excessive current flow c) due to the e.m.f source used d) due to lead wires View Answer Answer: d Explanation: Lead wires add to the resistance of the arms of the Wheatstone bridge. As a result the bridge circuit is destabilized and can’t be be used for signal conditioning. 9. How to minimize the drift in the value of resistance measured using a Wheatstone bridge? a) by using a high precision null detector b) by keeping the lead wire resistances within 0.2 mΩ c) by using a e.m.f source of minimum value d) by minimizing the flow of current View Answer Answer: b 4 of 5

3/19/18, 01:56



Explanation: The drift in the measured value of resistance in a Wheatstone bridge can be minimized by maintaining the lead wire resistances within 0.2 mΩ. As a result the effect of lead wire resistance gets removed in the output value of the bridge circuit. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:56

Low Resistance Measurement - Electrical Meas...


sanfoundry.com

Low Resistance Measurement Electrical Measurements Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Measurement of Low Resistance”. 1. Low resistance refers to _________ a) resistances of the order of 1ῼ b) resistances of the order of 1kῼ c) resistances of the order of 1mῼ d) resistances of the order of 1Mῼ View Answer Answer: a Explanation: Low resistance refers to resistances of the order of 1ῼ or less than that. Medium resistances range from above 1ῼ to a few kῼ. Any resistance value greater than a few kῼ is known as a high resistance. 2. What is the significance of measuring low resistances? a) voltage drop across the circuit is high b) and lead resistances are appreciable 1 of 6

3/19/18, 01:56



c) there is no power loss d) no current flows through the bridge circuit View Answer Answer: b Explanation: When measuring low resistances of the order of 1 ῼ or even less, lead and resistances of the order of even 0.002 ῼ cannot be neglected. High currents flow through low resistance circuits. 3. Fig 15.1 represents

a) construction of medium resistance b) construction of high resistance c) construction of low resistance d) construction of very low resistance View Answer Answer: c Explanation: Fig 15.1, illustrates the construction of low resistance. A is an ammeter used to measure current through the circuit, while V is the voltmeter used to measure voltage. 4. How is the voltage drop across a low resistance related

2 of 6

3/19/18, 01:56



to lead resistance? a) it contains resistance b) it depends on the magnitude of voltage drop c) it depends on the type of null detector used d) It does not contain any resistance View Answer Answer: d Explanation: The voltage drop measured across a low resistance does not contain any and lead resistances of the components and is independent of it. 5. Which is not a source of error in the measurement of low resistance? a) resistance drops at the leads b) thermal e.m.f c) temperature effect d) power dissipation through the circuit View Answer Answer: a Explanation: As the current flowing through a low resistance circuit is low, the voltage drop across the terminals due to and lead resistances is negligible. Thermal e.m.f occurs in a circuit when its temperature increases due to high current flow. 6. Which is the most popular method for measuring low resistance? a) ammeter-voltmeter method b) potentiometer method c) kelvin double bridge method 3 of 6

3/19/18, 01:56



d) ducter ohmmeter method View Answer Answer: c Explanation: Kelvin’s double bridge is used for the measurement of low resistances of the order of 1ῼ or less. Ammeter voltmeter method is used for the measurement of current flowing through and the voltage across the circuit. 7. How is the resistance related to the circuit while measuring a low resistance? a) independant of the type of the resistance b) it is negligible c) depends on the e.m.f source d) it is very high View Answer Answer: b Explanation: The and lead resistances form a part of the circuit whose resistance is very high. As a result the and lead resistances are usually neglected compared to the high resistance value. 8. In fig 15.1, the terminals aa’ are used for

4 of 6

3/19/18, 01:56



a) measuring the current flow through the circuit b) measuring the power dissipation of the circuit c) measuring the resistance of the circuit d) measuring the voltage drop across the resistance View Answer Answer: d Explanation: The terminals aa’ are used for the measurement of the voltage drop across the resistance R. An voltmeter V is connected across the terminals aa’. 9. In the below figure, the value of I is _________

a) I = IV + Ir b) I = IV – Ir c) I = IV Ir

d) I = IV ⁄ Ir View Answer Answer: a Explanation: By applying Kirchhoff’s current law at the node N from fig we get, I = IV + I r where, I is the total series current flowing through the circuit Iv is the current flowing through the voltmeter

5 of 6

3/19/18, 01:56



Ir is the current flowing through the resistance R. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

6 of 6

3/19/18, 01:56

Kelvin Bridge - Electrical Measurements Questi...


sanfoundry.com

Kelvin Bridge - Electrical Measurements Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Kelvin Bridge”. 1. Kelvin’s bridge consists of _________ a) double bridge b) single bridge c) half bridge d) three fourth bridge View Answer Answer: a Explanation: Kelvin’s bridge consists of two additional arms compared to a Wheatstone bridge. Hence it is also known as a double bridge. 2. The range of resistance measured in a Kelvin bridge is _________ a) 10Ω to 10 mΩ b) 1Ω to 10 µΩ 1 of 5

3/19/18, 01:57



c) 0.01Ω to 10 MΩ d) 0.1Ω to 10 nΩ View Answer Answer: b Explanation: Kelvin bridge is used for the measurement of low resistances. Low resistances vary in the range of 1Ω to 10 µΩ. 3. Accuracy of Kelvin bridge is of the order of _________ a) ±0.5 to ±2 % b) ±0.05 to ±0.02 % c) ±0.05 to ±0.2 % d) ±0.005 to ±0.02 % View Answer Answer: c Explanation: As Kelvin bridge is used for the measurement of low resistance values, the accuracy of measurement of low resistances in a Kelvin bridge is of the order of ±0.05 to ±0.2 %. 4. The balance equation of Kelvin bridge is

View Answer Answer: d Explanation: The balance equation in a Kelvin bridge is

2 of 5

3/19/18, 01:57



given by the relation Rx = R1R3⁄R2. where, R1, R2, R3, and Rx form the ratio arms Rx is the value of the unknown resistance. 5. What is the effect of load and resistance in Kelvin bridge? a) independent b) fully dependent c) partially dependent d) depends on the resistance value View Answer Answer: a Explanation: Effect of and lead resistances are completely eliminated in a Kelvin bridge as they don’t appear in the balance equation. Hence the Kelvin bridge is independent of the load and resistances. 6. The relation between ratio of resistance arms and ratio of resistance arms of second bridge is a) unequal b) equal c) twice d) one forth View Answer Answer: b Explanation: The relation between the ratio of the resistances of resistance arm and second resistance arm is equal for balance condition.

3 of 5

3/19/18, 01:57



7. Why Kelvin bridge is used for measurement of low resistance? a) due to e.m.f source used b) due to a large current flow c) due to and lead resistance d) due to power dissipation across the circuit View Answer Answer: c Explanation: While measuring very low resistances the and lead resistances cause significant errors in the value of the measured resistance. As a result Kelvin bridge is used for measurement of low resistances. 8. What is the condition to achieve a high sensitivity in a Kelvin bridge? a) low voltage b) high power c) medium resistance d) high current View Answer Answer: d Explanation: The condition to achieve a high sensitivity in a Kelvin bridge is that the measuring current should be high enough so as to sensitize the null detector. 9. Kelvin bridge can be calibrated to read a) inductance and Quality factor value b) capacitance only c) power and voltage d) current and frequency 4 of 5

3/19/18, 01:57



View Answer Answer: a Explanation: In its basic form a Kelvin bridge is used for the measurement of low resistance. A Kelvin bridge can be used for the measurement of inductance and Quality factor value through calibration. 10. Why can’t a Kelvin bridge be used for the measurement of low Quality factor value? a) due to thermoelectric effect b) due to balance problem c) due to the dull detector used d) due to temperature View Answer Answer: b Explanation: A Kelvin bridge can be used for the measurement of high Quality factor values. Due to bridge imbalance problem, Kelvin bridge can’t be used for measuring low Quality factor values. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:57

Megger - Electrical Measurements Questions a...


sanfoundry.com

Megger - Electrical Measurements Questions and Answers by Manish 4 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Megger”. 1. High resistances are of the order of __________ a) 0.1 Mῼ b) 10 mῼ c) 1 kῼ d) 10 Gῼ View Answer Answer: a Explanation: Resistances of the order of 0.1 Mῼ and above are known as high resistances. Resistance values upto 1 ῼ are known as low resistances. Resistances upto a few kῼ are known as medium resistances. 2. Megger is a ________ a) source of e.m.f b) source to measure high resistance c) type of a null detector

1 of 5

3/19/18, 01:57



d) current carrier View Answer Answer: b Explanation: Megger is a portable instrument to measure high resistances. 3. Megger is also used for ________ a) providing additional e.m.f b) bridge balance c) testing insulation resistance d) controlling the temperature View Answer Answer: c Explanation: A null detector is used to balance the bridge. Additional e.m.f can be provided to a circuit by increasing the magnitude of the voltage source. Megger is used for testing the insulation resistance of cables. 4. Megger works on the principle of ________ a) kirchhoff’s current laws b) ohm’s law c) gauss’s law d) electromagnetic induction View Answer Answer: d Explanation: Ohm’s law is applicable to only purely resistive circuits which are based on linearity principle. Megger basically works on the principle of electromagnetic induction.

2 of 5

3/19/18, 01:57



5. The role of the permanent magnet in a megger is to ________ a) provide field b) provide voltage c) generate power d) balance the circuit View Answer Answer: a Explanation: Voltage can be provided by means of an e.m.f source. Power generation occurs when current flows through a circuit. Permanent magnet in a megger is used to provide field for the generator as well as the ohmmeter. 6. A guard ring is provided in a megger to ________ a) protect the circuit b) eliminate error c) reduce current flow d) limit the temperature rise View Answer Answer: b Explanation: Temperature rise can be prevented by reducing the flow of excessive current through the circuit. The role of a guard ring in a megger is to reduce the errors due to leakage current. 7. The supply to the megger is given by ________ a) ac motor b) ac generator c) permanent magnet dc motor d) dc generator 3 of 5

3/19/18, 01:57



View Answer Answer: c Explanation: Megger works on the principle of electromagnetic induction. Supply can be given through a dc motor. A permanent magnet dc motor driven by hand is used as a source of supply to the megger. 8. The moving element of the ohmmeter in a megger consists of ________ a) 1 coil b) 4 coils c) 3 coils d) 10 coils View Answer Answer: c Explanation: The moving element of an ohmmeter in a megger consists of three coils, namely current or deflection coil, pressure or control coil and compensating coil. 9. The role of the compensating coil in a megger is ________ a) reduce current b) increase voltage c) control temperature d) scaling View Answer Answer: d Explanation: Temperature is controlled by minimising the flow of current through the circuit. Better scaling proportions can be achieved in a megger by making use of a 4 of 5

3/19/18, 01:57



compensating coil. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:57

Megger Applications - Electrical Measurements...


sanfoundry.com

Megger Applications - Electrical Measurements Questions and Answers by Manish 4-5 minutes

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Applications of Megger”. 1. Why is the scale of a megger calibrated in megaohms? a) to indicate resistance b) to minimise the current flow c) to increase the voltage drop d) to reduce the temperature View Answer Answer: a Explanation: Current flow through the circuit depends on the magnitude of the e.m.f source. In order to indicate the resistance value indicated by the pointer, the scale of a megger is calibrated. 2. Megger can be used for ing the electrical insulation level of a) ive components such as resistance, capacitor and 1 of 5

3/19/18, 01:57



inductance b) devices such as motor, cable, etc c) solid state devices d) liquid crystal devices View Answer Answer: b Explanation: Solid state devices consist of power electronic components and drives. One of the applications of a Megger circuit is in ing the electrical insulation levels of devices such as motor, cable, generator, etc. 3. Continuity between any two points can be measured using a) ammeter b) voltmeter c) megger d) galvanometer View Answer Answer: c Explanation: A galvanometer is used for detecting the balance condition in a bridge circuit. An ammeter measures the current flow through the circuit while the voltmeter is used for determining the voltage across the bridge circuit. A megger circuit can be used to determine the continuity between any two points. 4. Electrical continuity between any two points exists if a) there is current flow through them b) there is a wire connecting the points c) there is sufficient voltage drop 2 of 5

3/19/18, 01:57



d) pointer shows deflection View Answer Answer: d Explanation: Voltage drop across the circuit is measured by using a voltmeter. When the pointer displays full deflection, then there is an electrical continuity between the two points. 5. Megger is also known as _________ a) megaohmmeter b) multimeter c) galvanometer d) ammeter View Answer Answer: a Explanation: A galvanometer is used to detect the balance condition. A multimeter can be used for measurement of voltage, current, resistance and power. A megger is also known as a megaohmmeter as it is used for the measurement of resistances in the order of Mῼ. 6. The application of a megger is _________ a) to measure resistance b) to test for leakage c) to limit the current d) to increase the emf of the circuit View Answer Answer: b Explanation: Current flow through a circuit depends on the magnitude of the voltage source. Magnitude of the voltage source can be increased. A megger is mainly used for 3 of 5

3/19/18, 01:57



testing electrical leakages in wires. 7. What is the significance of a megger with respect to high resistance? a) it is used to limit the current b) it is used to provide stability c) used for measuring high resistance with respect to ground d) it is used for temperature protection View Answer Answer: c Explanation: Temperature protection can be provided to a bridge circuit by making use of heat sinks. Megger is used for determining very high resistances between the conducting part of a circuit and ground. 8. How is the megger calibrated? a) in steps of 1 unit per division b) based on the value of resistance to be measured c) directly calibrated on the position of the pointer d) reversely calibrated based on the pointer position View Answer Answer: d Explanation: The scale in a megger is calibrated such that normal position of a pointer indicates infinity while full scale corresponds to zero resistance. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements, here is

4 of 5

3/19/18, 01:57



complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:57

Electrical Measurements Aptitude Test - Sanfoundry


sanfoundry.com

Electrical Measurements Aptitude Test - Sanfoundry by Manish 4-5 minutes

This set of Electrical Measurements Questions and Answers for Aptitude test focuses on “Measurement of Earth Resistance”. 1. What is earthing? a) connecting electrical machines to earth b) providing a connection to the ground c) connecting the electrical machines to source d) providing a source of current View Answer Answer: a Explanation: Connecting electrical machines to the general mass of the earth by making use of a conducting material with very low resistance is known as earthing. 2. What is an earth electrode? a) electrode that is connected to earth b) material used for earthing c) electrode connected to the circuit d) electrode which is connected to the mains

1 of 5

3/19/18, 01:57



View Answer Answer: b Explanation: Electrode connected to the main is basically a source of e.m.f. Conducting material that is used for connecting electrical machinery to the earth is known as an earth electrode. 3. Earth electrode provides ____________ a) high resistance b) medium resistance c) low resistance d) very high resistance View Answer Answer: c Explanation: In the case of occurrence of any leakage currents due to poor shielding of the apparatus, the earth electrode is used to provide a very low resistance path from the electrical appliances to the earth. 4. How is the condition of an earth electrode measured? a) by measuring the voltage b) by measuring the current c) by measuring the power d) by measuring resistance View Answer Answer: d Explanation: The resistance of the earth electrode is measured in order to check whether it is in a good condition or not.

2 of 5

3/19/18, 01:57



5. In a three phase system, the neutral is _________ a) earthed b) connected to low voltage c) connected to high voltage d) not connected View Answer Answer: a Explanation: Earthing can be used to maintain a constant line voltage in a three phase system. This is achieved by earthing the neutral. 6. Earthing is used as return conductor in telephone lines and for traction work. a) True b) False View Answer Answer: a Explanation: The complications involved in laying separate telephone cables and the cast used for traction work is minimised. As a result earthing is used as a return conductor in telephone lines and for traction work. 7. Earthing does not help in protecting the equipment. a) True b) False View Answer Answer: b Explanation: Spike voltages occurring as a result of lightning or any other fault can be dissipated to ground by earthing, thus protecting the equipment. 3 of 5

3/19/18, 01:57



8. After earthing, the different parts of an electrical machinery are at _________ a) infinite potential b) intermediate potential c) zero potential d) undefined potential View Answer Answer: c Explanation: After earthing, the various parts of electrical machinery such as casing, armouring of cables, etc are at zero potential. 9. Connection of the various parts of a circuit to earth has a a) medium resistance b) high resistance c) very high resistance d) very low resistance View Answer Answer: d Explanation: Once an electrical apparatus is grounded, most of its components are at ground potential. When the different parts of an electrical machinery are connected to ground, they possess very low resistance. 10. Specific resistance of soil is _________ a) changes from soil to soil b) is constant c) depends on the circuit connected to it d) depends on the supply voltage View Answer 4 of 5

3/19/18, 01:57



Answer: a Explanation: Specific resistance depends on the nature and properties of a material. Specific resistance is different for various types of soils such as dry soil, rocky soil, wet soil, etc. Sanfoundry Global Education & Learning Series – Electrical Measurements. To practice all areas of Electrical Measurements for Aptitude test, here is complete set of 1000+ Multiple Choice Questions and Answers.

5 of 5

3/19/18, 01:57

Overview 3e4r5l

More details w3441

Related Documents 3m3m1z

Experiment 1 Measurement Of Resistance Lab 1 36gu

Measurement Of Stator Resistance Test 3z6e2g

Exp3 Earth Resistance Measurement 551z1y

More Documents from "kibrom atsbha" 1p2a4h

2. Questions On Measurement Of Inductance And Capacitance 20695f

12. Questions On Waveguides 535h2u

1. Questions And Answers On Basic Structures Of Computers p2i1l