**MRPL electrical 21-Feb-2021 question paper with solution**

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## All Questions and Answer of MRPL 21-feb-2021

#### A cell of emf x and internal resistance y is connected to a resistance y. The potential difference between the terminals of the cell is

- x/2
- x/2y
- 2x/y
- x/(x+y)

#### The ohm’s law deals with the relation between

- charge and resistance
- charge and capacity
- current and potential difference.
- capacity and potential difference.

#### Potential inside a hollow charged sphere is

- same as on its sphere
- greater than on its surface
- less than on its surface
- zero

#### Capacitance of a parallel plate capacitor decreases by

- increasing the area of plates
- increasing the distance between the plates
- putting a dielectric between the plates
- decreasing the distance between the plates

#### The capacitance of the two capacitors are in the ratio 1:2. When they are connected in parallel across supply voltage v, their charges will be in the ratio of

- 1:2
- 2:1
- 3:2
- 2:3

#### The capacity of a cell depends upon

- Nature of plates material and electrolyte
- Sizes of the plates and the quality of electrolyte
- Both (A) and (B)
- None of the above

#### When an organic compound is dissolved in water, the attractive forces between the charged atom reduce tremendously and they are separated this is called.

- Decomposition
- Deionisation
- Ionisation
- None of the above

#### Hysteresis loss in a magnetic material depends upon

- Area of hysteresis loop
- Frequency of reversed of field
- Volume of magnetic material
- All (A), (B) and (C)

#### Wheatstone bridge is used to measure

- Voltage
- Resistance
- Current
- Power

#### The three resistors each of r ohm are connected in star. When they are transformed into delta connections, the resistance of each arm will be

- 2R ohm
- 3R ohm
- 4R ohm
- R/2 ohm

#### When a source is delivering maximum power to the load, the efficiency will be

- Maximum
- Before 50%
- Above 50%
- 50%

#### An alternating quantity which attains its positive maximum value prior to the other is called the

- In phase quantity
- Lagging quantity
- Leading quantity
- None of the above

#### If a sinusoidal wave has frequency of 50 Hz with 15 ampere rms value. Which of the following equation represents?

- 15sin5Ot
- 30sin25t
- 42.42sin 100t
- 21.21sin314t

#### When a sinusoidal voltage is applied across a R-L series circuit having R XL, the phase angle will be

- 90°
- 0°
- 30°
- 45°

#### The shunt used in the millimetre

- Will extend the range and increases the resistance
- Will extend the range and decreases the meter resistance
- Will decrease the range and meter resistance
- Will decrease the range and increases the meter resistance

#### A signal of 10mV at 75MHz is to be measured. Which of the following instruments can be used

- VTVM
- Cathode rayoscilloscope
- Moving iron voltmeter
- Digital multimeter

#### The pressure coil of a dynamometer type wattmeter is

- Highly inductive
- Highly resistive
- Purely resistive
- Purely inductive

#### The dc series motors are preferred for traction applications because

- The torque is proportional armature current
- The torque is proportional to the square root of armature current
- The torque is proportional to square of armature Current and the speed is inversely proportional to the torque.
- Torque and speed are inversely proportional to armature current

#### What would happen if the field of d.c shunt motor is opened

- The speed of the motor will be reduced
- It will continue to run at its normal speed
- The speed of the motor becomes very high and may damage it.
- The current in the armature will decreases

#### The eddy current loss in the transformers occurs in the

- Primary winding
- Core
- Secondary winding
- None of the above

#### 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current will be:

- 0.2 Amp
- 5 Amp
- 10 Amp
- 20 Amp

#### The short circuit test in the transformers is performed to determine

- The iron loss at any load
- The hysteresis loss
- The copper loss at any load or any full load
- The eddy current loss

#### Regenerative method of braking is based on that

- Back emf is less than the applied voltage
- Back emf is equal to the applied voltage
- Back emf is more than the applied voltage
- None of the above

#### Which of the following can be used to control the speed of a d.c motor?

- Thermistor
- Thyristor
- Thyratron
- Transistor

#### Which of the following motors is most suitable for signaling devices and many kinds of timers

- d.c shunt motor
- d.c series motor
- Inductance motor
- Reluctance motor

#### Sparking at the commutators of a dc motor may result in

- Damage to the commutator’s segments
- Damage to the commutator’s insulation
- Increased power consumption
- All of the above

According to Fleming’s right hand rule for finding the direction induced emf, when induced finger points in the direction of induced emf, forefinger will point the direction of

- Motion of conductor
- Lines offorce
- Either of the above
- None of the above

#### The full load copper loss and iron loss of a transformer are 6400W and 5000W respectively the copper loss and iron loss at half load will be respectively.

- 3200W and 2500W
- 3200W and 5200W
- 1600W and 1250W
- 1600W and 5000W

#### A 6 pole, 3 phase alternator running at 1000rpm supplies to an 8 pole, 3 phase induction motor which has a rotor current of frequency 2Hz. The speed at which the motor operates is.

- 1000 rpm
- 960 rpm
- 750 rpm
- 720 rpm

#### The crawling in the induction motor Is caused by

- Improper design of stator lamination
- Low voltage supply
- High loads
- Harmonics developed in motor

#### The use of higher flux density in the transformer design

- Reduces the weight per kva
- Increases the weight per kva
- Has no relation with the weight of transformers
- Increases the weight per kw

#### In hard-tool applications which one of the following single-phase motors is used

- Shaded pole motor
- Capacitor start motor
- Capacitor run motor
- AC series motor

#### What is the angle between the induced voltage and supply voltage of a synchronous motor under running generation?

- Zero
- Greater than zero but =< 90°
- Between 90° and 180°

- 180°

#### How can reactive power delivered by a synchronous generator be controlled?

- By changing the prime moves input
- By changing the excitation
- By changing the direction of rotation
- By hanging the prime moves speed

#### When does a synchronous motor operate with leading power factor current?

- While it is under excited
- While it is critically excited
- While it is over excited
- While it is heavily loaded

#### In an induction motor what is the ratio of rotor copper-loss and rotor input

- 1/s
- s
- (1-s)
- s/(1-s)

#### What are the conditions to be satisfied for alternators to be synchronized with an incoming supply?

#### 1. Equal voltage

#### 2. Equal frequency

#### 3. Same power rating

#### 4. Same phase sequence

#### Select the correct answers using the code given below

- 2, 3 and 4
- 3 and 4
- 1, 2 and 3
- 1, 2 and 4

#### The pressure at the furnace is minimum in case of

- Force draught system
- Induced draught system
- Balanced draught system
- Natural draught System

#### The commonly used material of condenser tube is

- Aluminium
- Cast iron
- Admiralty brass
- Mild steel