Electrical Measurement and Instrumentation Viva

Electrical Measurement and Instrumentation viva-voce questions

Experiment No 1: Measurement of unknown resistance using Kelvin’s bridge. 1) What is the difference between AC and DC bridge? 2) What is the purpose of using Kelvin’s bridge? 3) What is Wheatstone’s bridge? 4) How resistances can be classified? 5) What do you mean by low resistance? 6) What do you mean by high resistance? 7) What do you mean by medium resistance? 8) How did you perform this experiment? 9) What are the examples of low resistance? 10) What are the examples of medium resistance? 11) What are the examples of high resistance? 12) What are other bridges used for the measurement of resistance? 13) What were the values of unknown resistances found by you? 14) What was the frequency of the source used in performing the experiment? 15) What is the formula for calculating unknown resistance using Kelvin’s bridge? 16) Which disadvantage of Wheatstone’s bridge is overcome in Kelvin’s bridge? 17) What was the amplitude of source which was used in performing the experiment? 18) Were the values of resistances found by you matched with the values provided by manufacturer? 19) What do you mean by balance condition in bridge circuit or when the bridge is said to be balanced? 20) Which device was used as a null detector in this experiment? 21) Was galvanometer showing exact zero in balanced condition? 22) What do you mean by balance condition of the bridge?

Experiment No 2: Measurement of unknown inductance using Maxwell’s inductance bridge. 1) 2) 3) 4) 5)

What was the amplitude of the source used in performing the experiment? What was the frequency of the source used in performing the experiment? How did you perform this experiment? What do you mean by quality factor of the coil? Which device was used as a null detector in this experiment?

6) What were the values of unknown inductances found by you? 7) Were the values inductances found by you matched with the values provided by manufacturer? 8) Define inductance? 9) What are the different types of inductor? 10) What are the two basic types of bridges? 11) Name any two DC bridge? 12) Name any three AC bridge? 13) Which devices we have used as a null detector in this experiment? 14) What was the inductance of the known inductor in the bridge circuit? 15) Hay’s bridge is used for the measurement of unknown _______________ 16) Was the source voltage variable or fixed in the experiment? 17) Was the source frequency variable or fixed in the experiment? 18) What was the type of unknown inductor? 19) What are the precautions we have to take while performing this experiment? 20)

Experiment No 3: Measurement of unknown inductance using Maxwell’s inductancecapacitance bridge. 1) Maxwell’s LC bridge is so called because for balance it employs two opposite impedances in opposite arms? True or False? 2) What was the amplitude of the source used in performing the experiment? 3) What was the frequency of the source used in performing the experiment? 4) How did you perform this experiment? 5) Inductance of an inductor is measured in terms of capacitance and resistance by _______bridge. 6) Which other methods are used for the measurement of inductance? 7) Which device was used as a null detector in this experiment? 8) What were the values of unknown inductances found by you? 9) Were the values of inductances by you matched with the values provided by manufacturer? 10) Which devices we have used as a null detector in this experiment? 11) What was the inductance of the known inductor in the bridge circuit? 12) Anderson’s bridge is used for the measurement of ____________ 13) How many variables were present in this experiment to obtain the balance condition of bridge?

14) Was the source voltage variable or fixed in the experiment? 15) Was the source frequency variable or fixed in the experiment? 16) What was the type of unknown inductor? 17) What are the precautions we have to take while performing this experiment? 18)

Experiment No: 4 Measurement of unknown capacitance using Schering’s bridge. 1) 2) 3) 4) 5) 6)

What was the amplitude of the source used in performing the experiment? What was the frequency of the source used in performing the experiment? How did you perform this experiment? Which device was used as a null detector in this experiment? What were the values of unknown capacitances found by you? Were the values capacitances found by you matched with the values provided by manufacturer? 7) Which devices we have used as a null detector in this experiment? 8) What was the capacitance of the known capacitor in the bridge circuit? 9) Owen’s bridge is used for the measurement of ______________ 10) Hay’s bridge is used for the measurement of ______________ 11) How many variables were present in this experiment to obtain the balance condition of bridge? 12) How many variables were present in this experiment to obtain the balance condition of bridge? 13) Was the source voltage variable or fixed in the experiment? 14) Was the source frequency variable or fixed in the experiment? 15) What was the type of unknown capacitor? 16) What are the precautions we have to take while performing this experiment? 17) 18) Experiment No 5: Measurement of unknown capacitance using De-Sauty’s bridge. 1) 2) 3) 4) 5)

What was the amplitude of the source used in performing the experiment? What was the frequency of the source used in performing the experiment? How did you perform this experiment? Which device was used as a null detector in this experiment? What were the values of unknown capacitances found by you?

6) Were the values of capacitances by you matched with the values provided by manufacturer? 7) Which devices we have used as a null detector in this experiment? 8) What was the capacitance of the known capacitor in the bridge circuit? 9) How many variables were present in this experiment to obtain the balance condition of bridge? 10) What are the precautions we have to take while performing this experiment? 11) Experiment No 6: Measurement of power in a three phase AC circuit by two wattmeter method. 1) Which are the two coils in a wattmeter? 2) Basically how do we connect pressure coil in the circuit? 3) Basically how do we connect current coil in the circuit? 4) How we find out multiplying factor of the wattmeter? 5) What is the advantage of this method over one wattmeter method? 6) What is blondel’s theorem? 7) What was the rating of the wattmeter used in the experiment? 8) How can you measure power factor with the help of this experiment? 9) What do you mean by power factor of the circuit? 10) Which type of circuit has lagging power factor? 11) Which type of circuit has leading power factor? 12) Which type of wattmeter is widely used? 13) What do you mean by balanced load? 14) What do you mean by unbalanced load? 15) Can we measure power in unbalanced load with this method? 16) Can we measure power in balanced load with this method? 17) What do you mean by phase? 18) According to principle of operation how many types of instruments are there? 19) What are the three basic essential features of the device? 20) What are the different types of controlling methods in an instrument? 21) What is the power factor of the load when one of the meters shows negative reading in two wattmeter method? 22) What is the power factor of the load when one of the meters shows zero reading in two wattmeter method? 23) What is the power factor of the load when both the meters show positive reading in two wattmeter method?

Experiment No 7: Measurement of power in a three phase AC circuit by single wattmeter method. 1) How did you perform this experiment? 2) What are the different types of damping methods in an instrument? 3) In an electrodynamometer type of wattmeters both the coils should be movable? True or False? 4) When we use low power factor wattmeter? 5) Which parameter of pressure coil produces error in electrodynamometer type of wattmeters? 6) What does L in a wattmeter terminals terminology stands for? 7) What does M in a wattmeter terminals terminology stands for? 8) What does V in a wattmeter terminals terminology stands for? 9) Which two points in a wattmeter are shorted? 10) What does ammeter shows active power or apparent power? 11) What does wattmeter reads, instantaneous power or average power? 12) The power indicated by wattmeter increases or decreases as we increase the load in load bank? 13) Can we calculate energy after measuring power with wattmeter? 14) What is the total range of wattmeter used? 15)

Experiment No 8: Measurement of line voltage, phase voltage, frequency and phase sequence of three phase supply of laboratory. 1) How did you perform this experiment? 2) What is vibration reed type frequency meter? 3) What do you mean by line voltage? 4) What do you mean by phase voltage? 5) What is the relationship between line voltage and phase voltage for a star connected load? 6) What is the relationship between line voltage and phase voltage for a delta connected load? 7) What is the relationship between line current and phase current for a star connected load? 8) What is the relationship between line current and phase current for a star connected load?

9) For a given load, if power factor of the load decreases, it will draws ___________ current from supply. (more/less) 10) Do we directly apply the AC supply to the load bank? Reason? 11) What is the purpose of variac in the experiment? 12) What are the precautions we have to take while performing this experiment? 13) How can we find out value of one division in an analog meter? 14) What do you mean by loading in electrical system? 15) What are the different types of load? 16) The power factor of a purely inductive load is __________? 17) The power factor of a purely capacitive load is _________? 18) The power factor of a purely resistive load is ___________? 19) What does ac ammeter reads, peak value or rms value? 20) What does ac voltmeter reads, peak value or rms value?