Electrical Measurements & Units Test Questions - 6

1)   The Q meter works on the principle of

a. Series resonance
b. Parallel resonance
c. Both (a) and (b)
d. Neither series resonance nor parallel resonance
Answer  Explanation  Related Ques

ANSWER: Series resonance

Explanation:
No explanation is available for this question!


2)   If C4 is the capacitance and R4 is the resistance of Hay’s bridge, then the Q factor of Hay’s bridge is given by

a. 1 / ωC4R4
b. ωC4R4
c. ωC4 / R4
d. ωR4 / C4
Answer  Explanation  Related Ques

ANSWER: 1 / ωC4R4

Explanation:
No explanation is available for this question!


3)   The Hay’s bridge is suitable for the measurement of inductances of coils with Q factor

a. More than 10
b. Less than 1
c. More than 1
d. Less than 10
Answer  Explanation  Related Ques

ANSWER: More than 10

Explanation:
No explanation is available for this question!


4)   Anderson bridge is suitable for the measurement of

a. Resistance
b. Inductance
c. Capacitance
d. All of these
Answer  Explanation  Related Ques

ANSWER: Inductance

Explanation:
No explanation is available for this question!


5)   The dielectric loss of pure capacitor is equal to

a. 1
b. 0
c. Maximum
d. None of these
Answer  Explanation  Related Ques

ANSWER: 0

Explanation:
No explanation is available for this question!


6)   If δ is the loss angle then the dissipation factor is given by

a. sin δ
b. cos δ
c. tan δ
d. cot δ
Answer  Explanation  Related Ques

ANSWER: tan δ

Explanation:
No explanation is available for this question!


7)   The Schering bridges can be used at

a. low voltage
b. high voltage
c. medium voltage
d. both (a) and (b)
Answer  Explanation  Related Ques

ANSWER: both (a) and (b)

Explanation:
No explanation is available for this question!


8)   The bridge suitable for the measurement of capacitance is /are

a. Anderson’s bridge
b. Hay’s bridge
c. Owen’s bridge
d. None of these
Answer  Explanation  Related Ques

ANSWER: None of these

Explanation:
No explanation is available for this question!


9)   Schering bridges are used for the measurement of

a. Unknown capacitance
b. Dielectric loss
c. Power factor
d. All of these
Answer  Explanation  Related Ques

ANSWER: All of these

Explanation:
No explanation is available for this question!


10)   The Ac Bridge which is used for the measurement of frequency is

a. Schering bridge
b. Wien bridge
c. Hay’s bridge
d. Anderson bridge
Answer  Explanation  Related Ques

ANSWER: Wien bridge

Explanation:
No explanation is available for this question!


11)   The Wien’s bridge is suitable for the measurement of frequency of the range of

a. Less than 100 Hz
b. 100 Hz to 100 kHz
c. 1 kHz to 100 MHz
d. More than 100 MHz
Answer  Explanation  Related Ques

ANSWER: 100 Hz to 100 kHz

Explanation:
No explanation is available for this question!


12)   For the measurement of unknown inductance in terms of known capacitance, the suitable ac bridges are

a. Maxwell and Schering bridge
b. Maxwell and Wien’s bridge
c. Maxwell and hay’s bridge
d. Hay’s and Wien’s bridge
Answer  Explanation  Related Ques

ANSWER: Maxwell and hay’s bridge

Explanation:
No explanation is available for this question!


13)   If a capacitor is connected across a portion of resistance of multiplier of the wattmeter then the pressure coil of the circuit becomes

a. Inductive
b. Non inductive
c. Capacitive
d. Non capacitive
Answer  Explanation  Related Ques

ANSWER: Non inductive

Explanation:
No explanation is available for this question!


14)   Shielding of the capacitor is done to

a. Make the value of capacitor definite
b. Balance the bridge without any problem
c. Both (a) and (b)
d. None of these
Answer  Explanation  Related Ques

ANSWER: Both (a) and (b)

Explanation:
No explanation is available for this question!


15)   In ac bridges, the Wagner earth devices are used to

a. Remove all the earth capacitances from the bridge circuit
b. Remove harmonics
c. Reduce error caused by stray electric field
d. All of these
Answer  Explanation  Related Ques

ANSWER: All of these

Explanation:
No explanation is available for this question!


16)   At 2 MHz, the resonance is obtained with a resonating capacitance value of 12 pF and at 400 kHz, the resonance is obtained with resonating capacitance value of 320 pF. Then the self capacitance of the coil is

a. 0.62 pF
b. 0.83 pF
c. 1.2 pF
d. 1.5 pF
Answer  Explanation  Related Ques

ANSWER: 0.62 pF

Explanation:
No explanation is available for this question!


17)   The given figure shows an ac bridge which is balanced at 100 Hz.

ac bridge

Fig : AC Bridge

The quality factor of the coil will be

a. 149
b. 159
c. 169
d. 189
Answer  Explanation  Related Ques

ANSWER: 159

Explanation:
No explanation is available for this question!


18)   In case of dc supply and in case of ac supply, the torque produced is

a. Directly proportional to power, inversely power to power
b. Directly proportional to power, directly proportional to power
c. Inversely proportional to power, inversely proportional to power
d. Inversely proportional to power, directly proportional to power
Answer  Explanation  Related Ques

ANSWER: Directly proportional to power, directly proportional to power

Explanation:
No explanation is available for this question!


19)   The scale of dynamometer wattmeter is

a. Approximately uniform
b. Cramped at the middle
c. Cramped at the end points
d. Crowded in the first half
Answer  Explanation  Related Ques

ANSWER: Approximately uniform

Explanation:
No explanation is available for this question!


20)   In standard wattmeters, the error caused by the voltage coil is overcome by

a. Connecting a high inductive resistance in series to the voltage coil
b. Connecting a high inductive resistance in parallel to the voltage coil
c. Connecting a compensating winding in series to the voltage coil
d. Connecting a compensating winding in parallel to the voltage coil
Answer  Explanation  Related Ques

ANSWER: Connecting a compensating winding in series to the voltage coil

Explanation:
No explanation is available for this question!


21)   In a dynamometer type wattmeter, the pressure coil connected across the load terminal is

a. Highly inductive
b. Highly capacitive
c. Highly resistive
d. Non inductive
Answer  Explanation  Related Ques

ANSWER: Highly resistive

Explanation:
No explanation is available for this question!


22)   The dynamometer wattmeter’s are

a. More accurate on dc supply
b. More accurate on ac supply
c. Equally accurate on both ac and dc supply
d. None of these
Answer  Explanation  Related Ques

ANSWER: Equally accurate on both ac and dc supply

Explanation:
No explanation is available for this question!


23)   Due to the inductance in the pressure coil of dynamometer type wattmeter, the reading will be

a. High for both leading and lagging power factors
b. Low for both leading and lagging power factors
c. High for lagging power factor and low for leading power factor
d. Low for lagging power factor and high for leading power factor
Answer  Explanation  Related Ques

ANSWER: High for lagging power factor and low for leading power factor

Explanation:
No explanation is available for this question!


24)   What will happen if the current coil and potential coil of dynamometer type wattmeter is interchanged?

a. Potential coil will get damaged
b. Current coil will get damaged
c. Both current coil and potential coil will get damaged
d. Neither potential coil nor current coil will get damaged
Answer  Explanation  Related Ques

ANSWER: Current coil will get damaged

Explanation:
No explanation is available for this question!


25)   In some wattmeters, a small capacitor is connected in parallel with the series resistor for

a. Reducing error due to inductance of the series resistor
b. Obtaining non inductive voltage coil current
c. Making resultant reactance capacitive
d. All of these
Answer  Explanation  Related Ques

ANSWER: All of these

Explanation:
No explanation is available for this question!


26)   In wattmeter’s, errors due to stray fields can be removed by

a. Proper instrument construction
b. Using brake magnet
c. Using shading ring
d. Using two separate ac magnets
Answer  Explanation  Related Ques

ANSWER: Proper instrument construction

Explanation:
No explanation is available for this question!


27)   A dynamometer type wattmeter reads 200W when its voltage coil is connected across the load whose voltage is 150 V. if the voltage coil has internal resistance of 1800 ohm, then the power taken by the load will be

a. 163.8 W
b. 171.7 W
c. 178.9 W
d. 187.5 W
Answer  Explanation  Related Ques

ANSWER: 187.5 W

Explanation:
No explanation is available for this question!


28)   In a dynamometer type meter, the error due to connections would be minimum if

a. Capacitive reactance of pressure coil is greater than its inductive reactance
b. Capacitive reactance of pressure coil is equal to its inductive reactance
c. Capacitive reactance of pressure coil is lesser than its inductive reactance
d. Capacitive reactance of current coil is equal to its inductive reactance
Answer  Explanation  Related Ques

ANSWER: Capacitive reactance of pressure coil is equal to its inductive reactance

Explanation:
No explanation is available for this question!


29)   To avoid wastage of power during calibration in dynamometer type wattmeter

a. Phantom loading is used
b. Brake magnet is used
c. Spring is used
d. Capacitance is used
Answer  Explanation  Related Ques

ANSWER: Phantom loading is used

Explanation:
No explanation is available for this question!


30)   Induction wattmeter’s can be used with

a. Only AC supply
b. Only DC supply
c. Both AC and DC supply
d. None of these
Answer  Explanation  Related Ques

ANSWER: Only AC supply

Explanation:
No explanation is available for this question!


31)   The frequency and supply voltage of induction wattmeter’s are

a. Constant, constant
b. Constant, variable
c. Variable, constant
d. Variable, variable
Answer  Explanation  Related Ques

ANSWER: Constant, constant

Explanation:
No explanation is available for this question!


32)   In induction type wattmeter both current and pressure coils are required. For obtaining the required phase difference

a. Shaded pole principle is used
b. Two separate ac magnets are used
c. Only one ac magnets are used
d. All of these
Answer  Explanation  Related Ques

ANSWER: Two separate ac magnets are used

Explanation:
No explanation is available for this question!


33)   The scale of induction wattmeter extends over

a. 70 degree
b. 120 degree
c. 180 degree
d. 300 degree
Answer  Explanation  Related Ques

ANSWER: 300 degree

Explanation:
No explanation is available for this question!


34)   A wattmeter has a pressure coil resistance of 5K ohm and current coil resistance of 0.02 ohm. What load will give equal error with the two connections if the load current is 15 A at a voltage of 240 V and 0.8 power factor

a. 20 A
b. 24 A
c. 28 A
d. 32 A
Answer  Explanation  Related Ques

ANSWER: 24 A

Explanation:
No explanation is available for this question!


35)   The readings of the two wattmeter used for the measurement of power input to a 3 phase induction motor are 850 W and 250 W respectively. The power factor of the motor is

a. 0.73
b. 0.76
c. 0.79
d. 0.85
Answer  Explanation  Related Ques

ANSWER: 0.73

Explanation:
No explanation is available for this question!


36)   What will be the power factor of an inductive load if the reading of the two wattmeters connected to measure input power of a 3 phase induction motor is 6: 3?

a. 0.86
b. 0.89
c. 0.91
d. 0.95
Answer  Explanation  Related Ques

ANSWER: 0.86

Explanation:
No explanation is available for this question!


37)   If the reading of the one wattmeter is four times the other wattmeter while measuring the input power of 3 phase induction motor then the power factor of the load will be

a. 0.56
b. 0.69
c. 0.74
d. 0.81
Answer  Explanation  Related Ques

ANSWER: 0.69

Explanation:
No explanation is available for this question!


38)   In L-C connected wattmeter, compensated coil is used. The error in the wattmeter is due to power consumed by the

a. Current coil
b. Potential coil
c. Inductor
d. Capacitor
Answer  Explanation  Related Ques

ANSWER: Potential coil

Explanation:
No explanation is available for this question!


39)   The full scale current of a galvanometer with internal resistance of 800 ohm is 8 A. what will be the multiplying power of 80 ohm shunt with this galvanometer?

a. 8
b. 9
c. 10
d. 11
Answer  Explanation  Related Ques

ANSWER: 11

Explanation:
No explanation is available for this question!


40)   If the reading of the two wattmeter’s is equal and opposite while measuring power in a 3 phase induction motor then the power factor of the load will be

a. Unity
b. Zero
c. 0.5 lagging
d. 0.5 leading
Answer  Explanation  Related Ques

ANSWER: Zero

Explanation:
No explanation is available for this question!