Electrical engineering/Network Theory Set-5 Sample Test,Sample questions

Question:
 In the expression of current in the R-L circuit the transient part is?

1.R/V

2.(V/R)(-exp⁡((R/L)t))

3.(V/R)(exp⁡((R/L)t))

4.V/R


Question:
A (350 A/7A), 50 Hz current transformer has a primary bar. The secondary has a pure resistance of 1 Ω. It also draws a current of 5 A. The magnetic core requires 350 AT for magnetization. Find the percentage ratio error.

1.10.56

2. -28.57

3.11.80

4.-11.80


Question:
A balanced delta-connected load of (2+j3) Ω per phase is connected to a balanced three-phase 440V supply. The phase current is 10A. Find the apparent power.

1.10955.67 VAR

2.10.95567 VAR

3.109.5567 VAR

4.1.095567 VAR


Question:
A balanced delta-connected load of (2+j3) Ω per phase is connected to a balanced three-phase 440V supply. The phase current is 10A. Find the total active power.

1.7.26W

2.726W

3.7260W

4.72.6W


Question:
A circuit resonates at 1 MHz It also has a Q of 100. Bandwidth between half power points is _____________

1.10 kHz

2.100 kHz

3.10 Hz

4.100 Hz


Question:
A coil is designed for high Q performance at a rated voltage and a specified frequency. If the frequency is made twice the original and the coil is operated at the same rated voltage, then the active power P will be affected as ____________

1.P is halved

2.P remains unchanged

3.P is doubled

4.P decreases 4 times


Question:
A coil is designed for high Q performance at a rated voltage and a specified frequency. If the frequency is made twice the original and the coil is operated at the same rated voltage, then the Q factor will be affected as ____________

1.Q is halved

2.Q remains unchanged

3.Q is doubled

4.Q increases or decreases but magnitude cannot be measured


Question:
A current of [2 + 2–√sin (314t + 30) + 22–√cos (952t +45)] is measured with a thermocouple type, 5A full scale, class 1 meter. The meter reading would lie in the range?

1.5 A ± 1 %

2. (2 + 32–√) A ± 1%

3.3 A ± 1.7 %

4.2 A ± 2.5 %


Question:
A single wattmeter is connected to measure the reactive power of a three-phase, three-wire balanced load. The line current is 17A and the line voltage is 440V. Calculate the power factor of the load if the reading of the wattmeter is 4488 VAR.

1.0.6

2.0.8

3.1

4.1.2


Question:
After how many time constants, the transient part reaches more than 99 percent of its final value?

1.2

2.3

3. 4

4.5


Question:
Determine the power (kW) drawn by the load.

1.21

2. 22

3.23

4.24


Question:
Each coil in three phase alternator has ________________ number of terminals.

1.2

2.4

3.6

4.8


Question:
If the roots of an equation are complex conjugate, then the response will be?

1.over damped

2.critically damped

3.damped

4.under damped


Question:
If the roots of an equation are real and equal, then the response will be?

1.over damped

2.damped

3.critically damped

4.under damped


Question:
If the roots of an equation are real and unequal, then the response will be?

1.critically damped

2.under damped

3.over damped

4.damped


Question:
If the system is a three-wire system, the currents flowing towards the load in the three lines must add to ___ at any given instant.

1.1

2. 2

3.3

4.zero


Question:
In a delta-connected load, the relation between line voltage and the phase voltage is?

1.line voltage > phase voltage

2. line voltage < phase voltage

3.line voltage = phase voltage

4.line voltage >= phase voltage


Question:
In a three phase alternator, there are __________ independent phase windings or coils.

1.1

2.2

3.3

4.4


Question:
In an R-C circuit, when the switch is closed, the response ____________

1.do not vary with time

2.decays with time

3.rises with time

4.first increases and then decreases


Question:
In the Delta or Mesh connection, there will be __________ number of common terminals.

1.1

2.2

3. 3

4.0


Question:
In three phase system at any given instant, the algebraic sum of three voltages must be?

1.0

2.1

3.2

4.3


Question:
In three phase system, the three voltages (currents) differ in phase by __________electrical degrees from each other in a particular sequence.

1.30

2.60

3.90

4.120


Question:
In wye or star connection _____________ of the three phases are joined together within the alternator.

1.similar ends

2.opposite ends

3.one similar end, two opposite ends

4.one opposite end, two opposite ends


Question:
Laplace transform changes the ____ domain function to the _____ domain function.

1.time, time

2.time, frequency

3.frequency, time

4.frequency, frequency


Question:
Phase sequence depends on the _________________

1.field

2.rotation of the field

3.armature

4.rotation of the armature


Question:
The CT supplies current to the current coil of a wattmeter power factor meter, energy meter and, an ammeter. These are connected as?

1.All coils in parallel

2.All coils in series

3.Series-parallel connection with two in each arm

4.Series-parallel connection with one in each arm


Question:
The expression of current in R-C circuit is?

1.i=(V/R)exp⁡(t/RC)

2.i=(V/R)exp⁡(-t/RC)

3.i=(V/R)-exp(⁡t/RC)

4.i=(V/R)-exp⁡(-t/RC)


Question:
The expression of current in R-L circuit is?

1.i=(V/R)(1+exp⁡((R/L)t))

2.i=-(V/R)(1-exp⁡((R/L)t))

3.i=-(V/R)(1+exp⁡((R/L)t))

4.i=(V/R)(1-exp⁡((R/L)t))


Question:
The four arms of an AC bridge network are as follows:
Arm AB: unknown impedance
Arm BC: standard capacitor C2 of 1000pf
Arm CD: a non-inductive resistance of R of 100 Ω in parallel to a capacitor of 0.01 μF
Arm DA: a non-inductive resistance of 1000 Ω
The supply frequency is 50 Hz and connected across terminals B and D. If the bridge is balanced with the above value, determine the value of unknown Impedance.

1.10 kΩ

2.100 kΩ

3.250 kΩ

4.20 kΩ


Question:
The input power to a three-phase load is 10kW at 0.8 Pf. Two watt meters are connected to measure the power. Find the reading of higher reading wattmeter.

1.7.165

2.6.165

3.6.165

4.4.165


Question:
The input power to a three-phase load is 10kW at 0.8 Pf. Two watt meters are connected to measure the power. Find the reading of lower reading wattmeter.

1.1.835

2.2.835

3.3.835

4.4.835


Question:
The percentage of power increased from single phase to three phase is?

1.50

2.100

3.150

4.200


Question:
The power generated by a machine increases _____________ percent from single phase to two phase.

1.40.4

2.41.4

3.42.4

4. 43.4


Question:
The readings of the two watt meters used to measure power in a capacitive load are -3000W and 8000W respectively. Calculate the input power. Assume RYB sequence.

1.5

2.50

3.500

4. 5000


Question:
The readings of the two watt meters used to measure power in a capacitive load are -3000W and 8000W respectively. Find the power factor.

1.0.25

2.0.5

3.0.75

4.1


Question:
The relation between the Q factor of a coil measured by the Q Meter and the actual Q of the coil is _________

1.Equal to

2.Same but somewhat lesser than

3.Same but somewhat higher than

4.Not equal to


Question:
The steady state part in the expression of current in the R-L circuit is?

1.(V/R)(exp⁡((R/L)t))

2.(V/R)(-exp⁡((R/L)t))

3.V/R

4.R/V


Question:
The time constant of an R-C circuit is?

1.RC

2.R/C

3.R

4.C


Question:
The unit step is not defined at t =?

1.0

2.1

3.2

4.3


Question:
The value of the time constant in the R-L circuit is?

1.L/R

2.R/L

3.R

4.L


Question:
The voltage between __________ and ___________ is called phase voltage.

1.line and line

2.line and reference

3. neutral point and reference

4.line and neutral point


Question:
The voltage between ______________ is called line voltage.

1.line and neutral point

2. line and reference

3.line and line

4.neutral point and reference


Question:
The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 400W and -35W. Calculate the total active power.

1.360

2.365

3. 370

4.375


Question:
The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 400W and -35W. Find the power factor.

1.0.43

2.0.53

3.0.63

4.0.73


Question:
The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 400W and -35W. Find the reactive power.

1.751.44

2.752.44

3.753.44

4.754.44


Question:
Two coils are having self-inductance of 5 mH and 10 mH and a mutual inductance of 0.5 mH in a differential connection. The equivalent inductance of the combination is ___________

1.14 mH

2.5.85 mH

3.6 mH

4.6.15 mH


Question:
Two resistances 100 ± 5Ω and 150 ± 15Ω are connected in series. If the error is specified as standard deviations, the resultant error will be ________________

1.±10 Ω

2.±10.6 Ω

3.±15.8 Ω

4.±20 Ω


Question:
When the power factor is __________ the power becomes zero 100 times a second in a 50Hz supply.

1.0

2.1

3.2

4.3


Question:
When two coupled coils of equal self-inductance are connected in series in one way the net inductance is 20 mH and when they are connected in the other way, the net inductance is 12 mH. The maximum value of net inductance when they are connected in parallel is __________

1.2 mH

2.5 mH

3.4 mH

4.6 mH


Question:
Which motors are called self-starting motors?

1.single phase

2.two phase

3. three phase

4.four phase


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