McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 151. |
The number of operations per hour in case of class IV contactor will be around |
| A. | 100 |
| B. | 600 |
| C. | 900 |
| D. | 1200. |
| Answer» D. 1200. | |
| 152. |
In case of contactors, the duty in which the main contacts remain closed for a period bearing a definition relation to the no-load periods, is known as |
| A. | Standard duty |
| B. | Intermittent duty |
| C. | Temporary duty |
| D. | Un-interrupted duty. |
| Answer» B. Intermittent duty | |
| 153. |
In case of contactors the ratio of the in service period to the entire period, expressed as a percentage is known as |
| A. | duty |
| B. | load factor |
| C. | class of contact |
| D. | none of the above. |
| Answer» B. load factor | |
| 154. |
A class I contactor should be mechanically sound to withstand |
| A. | 0.05 million times |
| B. | 0.25 million times |
| C. | 1.2 million times |
| D. | 5.0 million times. |
| Answer» B. 0.25 million times | |
| 155. |
Which of the following pair is used for frequency converters ? |
| A. | Squirrel cage induction motor and synchronous motor |
| B. | Wound rotor induction motor and synchronous motor |
| C. | Wound rotor induction motor and squirrel cage induction motor |
| D. | Any of the above. |
| Answer» A. Squirrel cage induction motor and synchronous motor | |
| 156. |
Belted wound rotor induction motors are preferred for |
| A. | machine tools |
| B. | gyratory crushers |
| C. | belt conveyor |
| D. | water pumps. |
| Answer» B. gyratory crushers | |
| 157. |
The cooling time constant is usually |
| A. | equal to the heating time constant |
| B. | more than heating time constant |
| C. | none of these. |
| D. | all |
| Answer» B. more than heating time constant | |
| 158. |
A motor of less than full load power rating can be used if the load is |
| A. | continuous duty |
| B. | short time duty |
| C. | intermittent periodic duty |
| D. | none of these. |
| Answer» B. short time duty | |
| 159. |
Pole changing method of speed control is used in |
| A. | slip ring induction motor |
| B. | dc shunt motor |
| C. | dc series motor |
| D. | squirrel cage induction motor. |
| Answer» D. squirrel cage induction motor. | |
| 160. |
To save the energy during braking |
| A. | dynamic braking is used |
| B. | plugging is used |
| C. | regenerative braking is used |
| D. | mechanical braking is used. |
| Answer» C. regenerative braking is used | |
| 161. |
To get speed higher than the base speed of the dc shunt motor |
| A. | armature resistance control is used |
| B. | field resistance control is used |
| C. | armature voltage control is used |
| D. | none of these. |
| Answer» B. field resistance control is used | |
| 162. |
Rotor resistance speed control is used in |
| A. | squirrel cage induction motor |
| B. | synchronous motor |
| C. | slip ring induction motor |
| D. | dc shunt motor. |
| Answer» C. slip ring induction motor | |
| 163. |
Effect of friction torque is more pronounced |
| A. | when the drive is running on full speed |
| B. | when the drive is being started |
| C. | when the drive is being stopped |
| D. | when the drive at half of its normal speed. |
| Answer» B. when the drive is being started | |
| 164. |
The equilibrium speed of a motor load system is obtained |
| A. | when motor torque equals the load torque |
| B. | when motor torque is less than the load torque |
| C. | when motor torque is more than the load torque |
| D. | none of the these. |
| Answer» A. when motor torque equals the load torque | |
| 165. |
Most commonly used ac motor is |
| A. | Synchronous motor |
| B. | Slip ring induction motor |
| C. | Squirrel cage induction motor |
| D. | ac commutator induction motor. |
| Answer» C. Squirrel cage induction motor | |
| 166. |
The motor commonly used in computers and digital systems is |
| A. | dc shunt motor |
| B. | Induction motor |
| C. | Stepper motor |
| D. | Synchronous motor. |
| Answer» B. Induction motor | |
| 167. |
Regenerative braking mode can be achieved in which quadrant (V-I curve)? |
| A. | Third |
| B. | Second |
| C. | Fourth |
| D. | First |
| Answer» B. Second | |
| 168. |
Fan type of loads exhibits which type of load torque characteristics? |
| A. | Constant torque characteristics |
| B. | Linearly rising torque characteristics |
| C. | Non-Linearly rising torque characteristics |
| D. | Non-Linearly decreasing torque characteristics |
| Answer» C. Non-Linearly rising torque characteristics | |
| 169. |
Type-A chopper is used for obtaining which type of mode? |
| A. | Motoring mode |
| B. | Regenerative braking mode |
| C. | Reverse motoring mode |
| D. | Reverse regenerative braking mode |
| Answer» A. Motoring mode | |
| 170. |
Boost converter is used to _________ |
| A. | Step down the voltage |
| B. | Step up the voltage |
| C. | Equalize the voltage |
| D. | Step up and step down the voltage |
| Answer» B. Step up the voltage | |
| 171. |
Reverse motoring mode is available in fourth quadrant. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» A. True | |
| 172. |
Which one is an example of variable loss? |
| A. | Windage loss |
| B. | Hysteresis loss |
| C. | Armature copper loss |
| D. | Friction loss |
| Answer» C. Armature copper loss | |
| 173. |
Load torques can be classified into how many types? |
| A. | Three |
| B. | Two |
| C. | Four |
| D. | Five |
| Answer» B. Two | |
| 174. |
Rolling mills exhibit what type of load torque characteristics? |
| A. | Constant torque characteristics |
| B. | Linearly rising torque characteristics |
| C. | Non-Linearly rising torque characteristics |
| D. | Non-Linearly decreasing torque characteristics |
| Answer» D. Non-Linearly decreasing torque characteristics | |
| 175. |
What is the relationship between torque and speed in constant type loads? |
| A. | Torque is independent of speed |
| B. | Torque linearly increases with increase in speed |
| C. | Torque non-linearly increases with an increase in speed |
| D. | Torque non-linearly decreases with an increase in speed |
| Answer» A. Torque is independent of speed | |
| 176. |
Torque inversely varies with the speed in the windage load torque component. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» B. False | |
| 177. |
What type of force handles for active torques? |
| A. | Strong nuclear forces |
| B. | Weak nuclear forces |
| C. | Gravitational forces |
| D. | Electrostatic forces |
| Answer» C. Gravitational forces | |
| 178. |
Passive torques always oppose the motion of the driven machine. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» A. True | |
| 179. |
Among the following which one exhibits linearly rising load torque characteristics? |
| A. | Elevators |
| B. | Rolling Mills |
| C. | Fan load |
| D. | Separately excited dc generator connected to the resistive load |
| Answer» D. Separately excited dc generator connected to the resistive load | |
| 180. |
What is the condition for the steady-state operation of the motor? |
| A. | Load torque > Motor torque |
| B. | Load torque <<<< Motor torque |
| C. | Load torque = Motor torque |
| D. | Load torque < Motor torque |
| Answer» C. Load torque = Motor torque | |
| 181. |
Choose the correct one. (* stands for multiplication, J represents the moment of inertia, w represents angular spee(D). |
| A. | J*d(w)/dt = Load torque – Motor torque |
| B. | J*d(w)/dt = Load torque + Motor torque |
| C. | J*d(w)/dt = Motor torque – Load torque |
| D. | J*d(w)/dt = Load torque * Motor torque |
| Answer» C. J*d(w)/dt = Motor torque – Load torque | |
| 182. |
In DC chopper, the waveform for input and output voltages is respectively __________ |
| A. | Discontinuous and Continuous |
| B. | Continuous and Discontinuous |
| C. | Both continuous |
| D. | Both discontinuous |
| Answer» B. Continuous and Discontinuous | |
| 183. |
A chopper behaves as a __________ |
| A. | DC equivalent of AC switching device |
| B. | DC equivalent of AC transformer |
| C. | DC equivalent of AC relay |
| D. | AC equivalent of circuit breaker |
| Answer» B. DC equivalent of AC transformer | |
| 184. |
A DC chopper feeds an RLE load. If the value of E is increased by 20%, the current ripple ________ |
| A. | increases by 20% |
| B. | decreases by 20% |
| C. | increases only 20% |
| D. | remains the same |
| Answer» D. remains the same | |
| 185. |
The conduction loss versus device current characteristic of a power MOSFET is best approximated by a ________ |
| A. | Straight line |
| B. | Rectangular hyperbola |
| C. | Parabola |
| D. | Exponential decaying functions |
| Answer» C. Parabola | |
| 186. |
Which of the following device is NOT suitable for parallel operation? |
| A. | MOSFET |
| B. | BJT |
| C. | IGBT |
| D. | TRIAC |
| Answer» B. BJT | |
| 187. |
SCR is uni-directional in nature. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» A. True | |
| 188. |
Which of the following device should be used as a switch in a low power switched mode power supply (SMPS)? |
| A. | GTO |
| B. | BJT |
| C. | MOSFET |
| D. | TRIAC |
| Answer» C. MOSFET | |
| 189. |
Servo motors are an example of which type of load? |
| A. | Pulsating loads |
| B. | Short time loads |
| C. | Impact loads |
| D. | Short time intermittent loads |
| Answer» B. Short time loads | |
| 190. |
Load torque of the crane is independent of _________ |
| A. | Speed |
| B. | Seebeck e�ect |
| C. | Hall e�ect |
| D. | Thomson e�ect |
| Answer» A. Speed | |
| 191. |
The unit of angular velocity is rad/s . |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» B. False | |
| 192. |
R.M.S value of the sinusoidal waveform V=V sin(ωt+α). |
| A. | V ÷2 |
| B. | V ÷2 |
| C. | V ÷2 |
| D. | V ÷3 |
| Answer» A. V ÷2 | |
| 193. |
Calculate the time period of the waveform x(t)=24sin(24πt+π÷4). |
| A. | .064 sec |
| B. | .047 sec |
| C. | .083 sec |
| D. | .015 sec |
| Answer» C. .083 sec | |
| 194. |
The turn-o times of the devices in increasing order is ___________
|
| A. | I, III, II, IV |
| B. | I, II, III, IV |
| C. | III, I, II, IV |
| D. | III, II, IV, I |
| Answer» A. I, III, II, IV | |
| 195. |
Which of the following devices should be used as a switch for high power and high voltage application? |
| A. | GTO |
| B. | MOSFET |
| C. | TRIAC |
| D. | Thyristor |
| Answer» D. Thyristor | |
| 196. |
Calculate the useful power developed by a motor using the given data: P = 3000 W, I = 60 A, R = .4 Ω. Assume frictional losses are 200 W and windage losses are 400 W. |
| A. | 970 W |
| B. | 960 W |
| C. | 980 W |
| D. | 990 W |
| Answer» B. 960 W | |
| 197. |
The consideration involved in the selection of the type of electric drive for a particular application depends on |
| A. | Speed control range and its nature |
| B. | Starting torque |
| C. | Environmental conditions |
| D. | All of the above. |
| Answer» D. All of the above. | |
| 198. |
Which of the following is preferred for automatic drives ? |
| A. | Synchronous motors |
| B. | Squirrel cage induction motor |
| C. | Ward Leonard controlled dc motors |
| D. | Any of the above. |
| Answer» C. Ward Leonard controlled dc motors | |
| 199. |
Which type of drive can be used for hoisting machinery |
| A. | AC slip ring motor |
| B. | Ward Leonard controlled DC shunt motor |
| C. | DC compound motor |
| D. | Any of the above. |
| Answer» D. Any of the above. | |
| 200. |
The motor normally used for crane travel is |
| A. | AC slip ring motor |
| B. | Ward Leonard controlled DC shunt motor |
| C. | Synchronous motor |
| D. | DC differentially compound motor. |
| Answer» A. AC slip ring motor | |
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