R4RIN – MCQs, Mock Tests | Electrical engineering Network Theory Set-5

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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 %

✅ Correct Answer: 3

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

✅ Correct Answer: 2

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

✅ Correct Answer: 2

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

1. 50
2. 100
3. 150
4. 200

✅ Correct Answer: 1

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

✅ Correct Answer: 2

Which motors are called self-starting motors?

1. single phase
2. two phase
3. three phase
4. four phase

✅ Correct Answer: 3

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

✅ Correct Answer: 4

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

1. 0
2. 1
3. 2
4. 3

✅ Correct Answer: 1

Phase sequence depends on the _________________

1. field
2. rotation of the field
3. armature
4. rotation of the armature

✅ Correct Answer: 2

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

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 3

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

1. 2
2. 4
3. 6
4. 8

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 4

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

✅ Correct Answer: 3

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

1. 1
2. 2
3. 3
4. 0

✅ Correct Answer: 4

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

✅ Correct Answer: 3

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

Determine the power (kW) drawn by the load.

1. 21
2. 22
3. 23
4. 24

✅ Correct Answer: 4

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

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 1

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

✅ Correct Answer: 2

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

✅ Correct Answer: 4

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

✅ Correct Answer: 1

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

✅ Correct Answer: 2

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))

✅ Correct Answer: 4

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

✅ Correct Answer: 3

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

✅ Correct Answer: 2

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

1. L/R
2. R/L
3. R
4. L

✅ Correct Answer: 1

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

✅ Correct Answer: 4

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)

✅ Correct Answer: 2

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

✅ Correct Answer: 2

The time constant of an R-C circuit is?

1. RC
2. R/C
3. R
4. C

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 4

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

✅ Correct Answer: 3

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

1. time, time
2. time, frequency
3. frequency, time
4. frequency, frequency

✅ Correct Answer: 2

The unit step is not defined at t =?

1. 0
2. 1
3. 2
4. 3

✅ Correct Answer: 1