Code No: RR310202 RR Set No. 2
III B.Tech I Semester Supplementary Examinations,June 2010
ELECTRICAL MEASUREMENTS Electrical And Electronics Engineering
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) Explain the different types of tests that are carried on a single phase induction
type watt hour meters. Describe the long period dial test.
(b) A 230V, 1φ, watt hour meter has a constant load of 4A passing through it for 6 hours at unity pf. If the meter disc makes 2208 revolutions during this period. What is the meter constant in revolutions per kwh? Calculate the pf of the load if the number of revolutions made by the meter are 1472 when operating at 230V & 5A for 4 hours. [8+8]
2. (a) In Maxwell's Inductance-capacitance bridge the dial of variable capacitor can
be made to read the value of unknown inductance directly? How is it done?
(b) A Maxwell's inductance capacitance bridge is used to measure an unknown
inductance in comparison with capacitance.
The various values at balance are
R2 of arm ad =400Ω
R3 of arm bc = 600Ω
R4 and C4 of arm cd = 1000Ω, 0.5 µ
Calculate the values of R1 and L1 of arm ab and also the value of storage
(Φ) factor of coil if requency is 1000Hz. [8+8]
3. (a) Show that in two wattmeter method of 3 phase power measurement the sum of the readings of the two wattmeters gives the total power consumed in a 3
phase circuit. Hence prove tan θ =√3 W1 − W2
1 2
where φ is the phase angle of the
load and w1 and w2 are the readings of the wattmeters.
(b) In a balanced three phase system power is measured by two wattmeter method
& the ratio of two wattmeter readings is 2:1 Determine the power factor of
the system & deduce the relation used. [8+8]
4. (a) What are permeameters? Explain the working of a Hopkinson permeameter.
(b) Explain the different methodologies used for testing the bar specimens as
compared to the ring specimens with respect to magnetic materials. [8+8]
5. Describe the construction and working of a polar type potentiometer. How is it standardized? What are the functions of the transfer instrument and the phase shifting transformer? [16]
6. (a) Explain the working of a moving iron ammeter with the help of a neat diagram.
Derive the expression for the deflecting torque of a moving iron ammeter in
terms of current and rate of change of inductance with deflection.
1
Code No: RR310202 RR Set No. 2
(b) What are the main sources of errors in the above instrument? specify the methods adopted to reduce the same. [8+8]
7. (a) Explain how the range of electrostatic voltmeters can be extended by using
Resistance and Capacitance potential dividers.
(b) An electrostatic voltmeter consists of two attracted plates one movable and the other fixed. Both the plates are provided with guard rings so as to make edge effects negligible. It is observed that the application of 10kV between the plates results in a pull of 5× 10−3 N on the movable plate. Find the change in capacitance resulting from change in position of the movable plate by 1mm. Diameter of movable plate is 100mm. [8+8]
8. (a) Explain the construction and working of a Moving Iron type power factor
meters.
(b) Describe the construction and working of Weston type synchroscope. [8+8]
? ? ? ? ?
2
Code No: RR310202 RR Set No. 4
III B.Tech I Semester Supplementary Examinations,June 2010
ELECTRICAL MEASUREMENTS Electrical And Electronics Engineering
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Describe the construction and working of a polar type potentiometer. How is it standardized? What are the functions of the transfer instrument and the phase shifting transformer? [16]
2. (a) What are permeameters? Explain the working of a Hopkinson permeameter. (b) Explain the different methodologies used for testing the bar specimens as
compared to the ring specimens with respect to magnetic materials. [8+8]
3. (a) Explain the working of a moving iron ammeter with the help of a neat diagram.
Derive the expression for the deflecting torque of a moving iron ammeter in terms of current and rate of change of inductance with deflection.
(b) What are the main sources of errors in the above instrument? specify the methods
adopted to reduce the same. [8+8]
4. (a) In Maxwell's Inductance-capacitance bridge the dial of variable capacitor can
be made to read the value of unknown inductance directly? How is it done?
(b) A Maxwell's inductance capacitance bridge is used to measure an unknown
inductance in comparison with capacitance. The various values at balance are
R2 of arm ad =400Ω
R3 of arm bc = 600Ω
R4 and C4 of arm cd = 1000Ω, 0.5 µ
Calculate the values of R1 and L1 of arm ab and also the value of storage
(Φ) factor of coil if requency is 1000Hz. [8+8]
5. (a) Show that in two wattmeter method of 3 phase power measurement the sum of the readings of the two wattmeters gives the total power consumed in a 3
phase circuit. Hence prove tan θ =√3 W1 − W2
1 2
where φ is the phase angle of the
load and w1 and w2 are the readings of the wattmeters.
(b) In balanced three phase system power is measured by two wattmeter method
& the ratio of two wattmeter readings is 2:1 Determine the power factor of
the system & deduce the relation used. [8+8]
6. (a) Explain the construction and working of a Moving Iron type power factor
meters.
(b) Describe the construction and working of Weston type synchroscope. [8+8]
7. (a) Explain the different types of tests that are carried on a single phase induction type watt hour meters. Describe the long period dial test.
3
Code No: RR310202 RR Set No. 4
(b) A 230V, 1φ, watt hour meter has a constant load of 4A passing through it for 6 hours at unity pf. If the meter disc makes 2208 revolutions during this period. What is the meter constant in revolutions per kwh? Calculate the pf of the load if the number of revolutions made by the meter are 1472 when operating at 230V & 5A for 4 hours. [8+8]
8. (a) Explain how the range of electrostatic voltmeters can be extended by using
Resistance and Capacitance potential dividers.
(b) An electrostatic voltmeter consists of two attracted plates one movable and the other fixed. Both the plates are provided with guard rings so as to make edge effects negligible. It is observed that the application of 10kV between the plates results in a pull of 5× 10−3 N on the movable plate. Find the change in capacitance resulting from change in position of the movable plate by 1mm. Diameter of movable plate is 100mm. [8+8]
? ? ? ? ?
4
Code No: RR310202 RR Set No. 1
III B.Tech I Semester Supplementary Examinations,June 2010
ELECTRICAL MEASUREMENTS Electrical And Electronics Engineering
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) Show that in two wattmeter method of 3 phase power measurement the sum
of the readings of the two wattmeters gives the total power consumed in a 3
phase circuit. Hence prove tan θ =√3 W1 − W2
1 2
where φ is the phase angle of the
load and w1 and w2 are the readings of the wattmeters.
(b) In balanced three phase system power is measured by two wattmeter method
& the ratio of two wattmeter readings is 2:1 Determine the power factor of the system & deduce the relation used. [8+8]
2. (a) Explain how the range of electrostatic voltmeters can be extended by using
Resistance and Capacitance potential dividers.
(b) An electrostatic voltmeter consists of two attracted plates one movable and the other fixed. Both the plates are provided with guard rings so as to make edge effects negligible. It is observed that the application of 10kV between the plates results in a pull of 5× 10−3 N on the movable plate. Find the change in capacitance resulting from change in position of the movable plate by 1mm. Diameter of movable plate is 100mm. [8+8]
3. (a) Explain the construction and working of a Moving Iron type power factor meters.
(b) Describe the construction and working of Weston type synchroscope. [8+8]
4. (a) What are permeameters? Explain the working of a Hopkinson permeameter. (b) Explain the different methodologies used for testing the bar specimens as
compared to the ring specimens with respect to magnetic materials. [8+8]
5. (a) Explain the different types of tests that are carried on a single phase induction type watt hour meters. Describe the long period dial test.
(b) A 230V, 1φ, watt hour meter has a constant load of 4A passing through it for 6 hours at unity pf. If the meter disc makes 2208 revolutions during this period. What is the meter constant in revolutions per kwh? Calculate the pf of the load if the number of revolutions made by the meter are 1472 when operating at 230V & 5A for 4 hours. [8+8]
6. Describe the construction and working of a polar type potentiometer. How is it standardized? What are the functions of the transfer instrument and the phase shifting transformer? [16]
5
Code No: RR310202 RR Set No. 1
7. (a) Explain the working of a moving iron ammeter with the help of a neat diagram.
Derive the expression for the deflecting torque of a moving iron ammeter in terms of current and rate of change of inductance with deflection.
(b) What are the main sources of errors in the above instrument? specify the methods adopted to reduce the same. [8+8]
8. (a) In Maxwell's Inductance-capacitance bridge the dial of variable capacitor can be made to read the value of unknown inductance directly? How is it done?
(b) A Maxwell's inductance capacitance bridge is used to measure an unknown
inductance in comparison with capacitance. The various values at balance are
R2 of arm ad =400Ω
R3 of arm bc = 600Ω
R4 and C4 of arm cd = 1000Ω, 0.5 µ
Calculate the values of R1 and L1 of arm ab and also the value of storage
(Φ) factor of coil if requency is 1000Hz. [8+8]
? ? ? ? ?
6
Code No: RR310202 RR Set No. 3
III B.Tech I Semester Supplementary Examinations,June 2010
ELECTRICAL MEASUREMENTS Electrical And Electronics Engineering
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Describe the construction and working of a polar type potentiometer. How is it standardized? What are the functions of the transfer instrument and the phase shifting transformer? [16]
2. (a) What are permeameters? Explain the working of a Hopkinson permeameter. (b) Explain the different methodologies used for testing the bar specimens as
compared to the ring specimens with respect to magnetic materials. [8+8]
3. (a) Explain the different types of tests that are carried on a single phase induction type watt hour meters. Describe the long period dial test.
(b) A 230V, 1φ, watt hour meter has a constant load of 4A passing through it for 6 hours at unity pf. If the meter disc makes 2208 revolutions during this period. What is the meter constant in revolutions per kwh? Calculate the pf of the load if the number of revolutions made by the meter are 1472 when operating at 230V & 5A for 4 hours. [8+8]
4. (a) Explain the construction and working of a Moving Iron type power factor
meters.
(b) Describe the construction and working of Weston type synchroscope. [8+8]
5. (a) Show that in two wattmeter method of 3 phase power measurement the sum of the readings of the two wattmeters gives the total power consumed in a 3
phase circuit. Hence prove tan θ =√3 W1 − W2
1 2
where φ is the phase angle of the
load and w1 and w2 are the readings of the wattmeters.
(b) In balanced three phase system power is measured by two wattmeter method
& the ratio of two wattmeter readings is 2:1 Determine the power factor of
the system & deduce the relation used. [8+8]
6. (a) Explain how the range of electrostatic voltmeters can be extended by using
Resistance and Capacitance potential dividers.
(b) An electrostatic voltmeter consists of two attracted plates one movable and the other fixed. Both the plates are provided with guard rings so as to make edge effects negligible. It is observed that the application of 10kV between the plates results in a pull of 5× 10−3 N on the movable plate. Find the change in capacitance resulting from change in position of the movable plate by 1mm. Diameter of movable plate is 100mm. [8+8]
7. (a) In Maxwell's Inductance-capacitance bridge the dial of variable capacitor can be made to read the value of unknown inductance directly? How is it done?
7
Code No: RR310202 RR Set No. 3
(b) A Maxwell's inductance capacitance bridge is used to measure an unknown inductance in comparison with capacitance.
The various values at balance are
R2 of arm ad =400Ω
R3 of arm bc = 600Ω
R4 and C4 of arm cd = 1000Ω, 0.5 µ
Calculate the values of R1 and L1 of arm ab and also the value of storage
(Φ) factor of coil if requency is 1000Hz. [8+8]
8. (a) Explain the working of a moving iron ammeter with the help of a neat diagram.
Derive the expression for the deflecting torque of a moving iron ammeter in
terms of current and rate of change of inductance with deflection.
(b) What are the main sources of errors in the above instrument? specify the methods
adopted to reduce the same. [8+8]
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