McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering , Electronics and Communication Engineering .
| 101. |
Which device can be used in a chopper circuit? |
| A. | BJT |
| B. | MOSFET |
| C. | GTO |
| D. | All of the mentioned |
| Answer» D. All of the mentioned | |
| 102. |
A chopper is a |
| A. | Time ratio controller |
| B. | AC to DC converter |
| C. | DC transformer |
| D. | High speed semiconductor switch |
| Answer» D. High speed semiconductor switch | |
| 103. |
What is the duty cycle of a chopper ? |
| A. | Ton/Toff |
| B. | Ton/T |
| C. | T/Ton |
| D. | Toff x Ton |
| Answer» B. Ton/T | |
| 104. |
The load voltage of a chopper can be controlled by varying the |
| A. | duty cycle |
| B. | firing angle |
| C. | reactor position |
| D. | extinction angle |
| Answer» A. duty cycle | |
| 105. |
The values of duty cycle (α) lies between |
| A. | 0<α<1 |
| B. | 0>α>-1 |
| C. | 0<=α<=1 |
| D. | 1<α<100 |
| Answer» C. 0<=α<=1 | |
| 106. |
If T is the time period for a chopper circuit and α is its duty cycle, then the chopping frequency is |
| A. | Ton/α |
| B. | Toff/α |
| C. | α/Toff |
| D. | α/Ton |
| Answer» D. α/Ton | |
| 107. |
AC voltage controllers convert |
| A. | Fixed ac to fixed dc |
| B. | Variable ac to variable dc |
| C. | Fixed ac to variable ac |
| D. | Variable ac to fixed ac |
| Answer» C. Fixed ac to variable ac | |
| 108. |
In AC voltage controllers the |
| A. | variable ac with fixed frequency is obtained |
| B. | variable ac with variable frequency is obtained |
| C. | variable dc with fixed frequency is obtained |
| D. | variable dc with variable frequency is obtained |
| Answer» A. variable ac with fixed frequency is obtained | |
| 109. |
The GTO (gate turn-off thyristor) is a |
| A. | p-n-p-n device |
| B. | p-n-p device |
| C. | p-metal-n device |
| D. | p-n single junction device |
| Answer» A. p-n-p-n device | |
| 110. |
The GTO can be turned off |
| A. | by a positive gate pulse |
| B. | by a negative gate pulse |
| C. | by a negative anode-cathode voltage |
| D. | by removing the gate pulse |
| Answer» B. by a negative gate pulse | |
| 111. |
In GTO The anode current is ideally limited by the |
| A. | gate pulse amplitude |
| B. | internal impedance of the device |
| C. | load Impedance |
| D. | gate circuit impedance |
| Answer» C. load Impedance | |
| 112. |
In a GTO the n+ layer forms the |
| A. | anode & gate |
| B. | cathode & gate |
| C. | cathode |
| D. | gate |
| Answer» C. cathode | |
| 113. |
The turn-off gain βoff of the GTO is given by |
| A. | Ig/Ia |
| B. | Ia/Ig |
| C. | Vg/Va |
| D. | Vg/Va |
| Answer» B. Ia/Ig | |
| 114. |
A GTO can be represented by two transistors T1 & T2. The current gain of both transistors are α1 and α2 respectively. A low value of gate current requires |
| A. | low value of α1 and α2 |
| B. | low value of α1 and high value of α2 |
| C. | high value of α1 and low value of α2 |
| D. | high values of α1 and α2 |
| Answer» B. low value of α1 and high value of α2 | |
| 115. |
Gold doped GTOs have _____________ as compared to the conventional GTOs |
| A. | high turn-off time |
| B. | low negative gate current requirement |
| C. | low reverse voltage blocking capabilities |
| D. | lower positive gate current requirement |
| Answer» B. low negative gate current requirement | |
| 116. |
Latching current for the GTOs is ________ as compared to CTs (Conventional thyristors). |
| A. | more |
| B. | less |
| C. | constant |
| D. | cannot be said |
| Answer» A. more | |
| 117. |
In case of the two-transistor model (T1 & T2) of GTO with anode-short, the anode-short is placed between the |
| A. | emitter of T1 & T2 |
| B. | emitter of T1 & base of T2 |
| C. | emitter of T1 & base of T1 |
| D. | emitter of T1 & collector of T2 |
| Answer» C. emitter of T1 & base of T1 | |
| 118. |
Choose the correct statement: GTOs have _________ as compared to the CTs. |
| A. | less on-state voltage drop |
| B. | less gate drive losses |
| C. | higher reverse blocking capabilities |
| D. | faster switching speed |
| Answer» D. faster switching speed | |
| 119. |
A single-phase voltage controller, using one SCR in anti parallel with a diode, feeds a load R and Vs = 230 V. For a firing angel of 90° for the SCR, the PMMC voltage connected across R would read |
| A. | 0 |
| B. | 51.8 V |
| C. | –51.8 V |
| D. | –36.82 V |
| Answer» C. –51.8 V | |
| 120. |
A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the average value of SCR current. |
| A. | 21.68 A |
| B. | 200 mA |
| C. | 4.14 A |
| D. | 2.07 A |
| Answer» C. 4.14 A | |
| 121. |
An IGBT has three terminals called: |
| A. | Collector, Emitter and Base |
| B. | Drain, Source and Base |
| C. | Drain, Source and Gate |
| D. | Collector, Emitter and Gate |
| Answer» D. Collector, Emitter and Gate | |
| 122. |
The function of snubber circuit connected across the SCR is to: |
| A. | Suppress dv/dt |
| B. | Increase dv/dt |
| C. | Decrease dv/dt |
| D. | Decrease di/dt |
| Answer» A. Suppress dv/dt | |
| 123. |
An UJT exhibits negative resistance region: |
| A. | Before the break point |
| B. | Between peak and valley point |
| C. | After the valley point |
| D. | Both (a) and (c) |
| Answer» B. Between peak and valley point | |
| 124. |
For dynamic equalizing circuit used for series connected SCRs, the choice of C is based on: |
| A. | Reverse recovery characteristics |
| B. | Turn-on characteristics |
| C. | Turn-off characteristics |
| D. | Rise time characteristics |
| Answer» A. Reverse recovery characteristics | |
| 125. |
A four quadrant operation require: |
| A. | Two full converters in series |
| B. | Two full converters connected back to back |
| C. | Two full converters connected in parallel |
| D. | Two semi conductors connected back to back |
| Answer» B. Two full converters connected back to back | |
| 126. |
In a circulating-current type of dual converter, the nature of the voltage across the reactor is: |
| A. | Alternating |
| B. | Pulsating |
| C. | Direct |
| D. | Triangular |
| Answer» A. Alternating | |
| 127. |
The frequency of the ripple in the output voltage of 3-phase semiconductor depends on: |
| A. | Firing angle and load resistance |
| B. | Firing angle and load inductance |
| C. | The load circuit parameters |
| D. | Firing angle and the supply frequency |
| Answer» D. Firing angle and the supply frequency | |
| 128. |
A single-phase full bridge inverter can operate in load-commutation mode in case load consists of: |
| A. | RL load |
| B. | RLC underdamped |
| C. | RLC damped |
| D. | RLC critically damped |
| Answer» B. RLC underdamped | |
| 129. |
Practical way of obtaining static voltage equalization in series connected SCRs is by the use of: |
| A. | One resistor across the string |
| B. | Resistors of different values across each SCR |
| C. | Resistors of the same value across each SCR |
| D. | One resistor in series with each SCR |
| Answer» C. Resistors of the same value across each SCR | |
| 130. |
A resistor connected across the gate and cathode of an SCR in a circuit increases its |
| A. | dv/dt rating |
| B. | Holding current |
| C. | Noise Immunity |
| D. | Turn-off time |
| Answer» C. Noise Immunity | |
| 131. |
In thyristor, holding current is: |
| A. | more than the latching current |
| B. | less than the latching current |
| C. | equal to latching current |
| D. | none of the above |
| Answer» B. less than the latching current | |
| 132. |
When a thyristor turn on, the gate drive: |
| A. | can be turned down but thyristor remains in on position |
| B. | cannot be turned down as thyristor will be turned off |
| C. | gate drive has no impact on starting and turning off the thyristor |
| D. | none of the above |
| Answer» A. can be turned down but thyristor remains in on position | |
| 133. |
A thyristor can be termed as: |
| A. | DC switch |
| B. | AC switch |
| C. | both AC and DC switch |
| D. | none of the above |
| Answer» A. DC switch | |
| 134. |
During forward blocking state, a thyristor is associated with: |
| A. | large current and low voltage |
| B. | low current and large voltage |
| C. | medium current and large voltage |
| D. | None of the above |
| Answer» B. low current and large voltage | |
| 135. |
Turn-off time of an SCR is measured from the instant: |
| A. | anode current becomes zero |
| B. | anode voltage becomes zero |
| C. | anode voltage and anode current becomes zero |
| D. | gate current becomes zero |
| Answer» A. anode current becomes zero | |
| 136. |
A forward voltage can be applied to an SCR after its: |
| A. | anode current reduces to zero |
| B. | gate recovery time |
| C. | reverse recovery time |
| D. | anode voltage reduces to zero |
| Answer» B. gate recovery time | |
| 137. |
In a thyristor, the magnitude of the anode current will: |
| A. | increase if the gate current is increased |
| B. | decrease if the gate current is decreased |
| C. | increase if gate current is decreased |
| D. | no change with the variation of the gate current |
| Answer» D. no change with the variation of the gate current | |
| 138. |
In a thyristor, ratio of latching current to holding current is: |
| A. | 0.4 |
| B. | 1.0 |
| C. | 2.5 |
| D. | 4.0 |
| Answer» C. 2.5 | |
| 139. |
Once SCR starts conducting a forward current, its gate losses control over: |
| A. | anode circuit voltage only |
| B. | anode circuit current only |
| C. | anode circuit voltage and current |
| D. | none of the above |
| Answer» C. anode circuit voltage and current | |
| 140. |
On state voltage drop across thyristor used in a 230 V supply system is of the order: |
| A. | 110-115V |
| B. | 250 V |
| C. | 1- 1.5 V |
| D. | none of the above |
| Answer» C. 1- 1.5 V | |
| 141. |
Silicon controlled rectifier can be turned on |
| A. | By applying a gate pulse and turned off only when current becomes zero |
| B. | And turned off by applying gate pulse |
| C. | By applying a gate pulse and turned off by removing the gate pulse |
| D. | By making current non zero and turned off by making current zero |
| Answer» A. By applying a gate pulse and turned off only when current becomes zero | |
| 142. |
TRIAC is a semiconductor power electronic device which contains |
| A. | Two SCR’s connected in reverse parallel |
| B. | Two SCR’s connected in parallel |
| C. | Two SCR’s connected in series |
| D. | Two BJT’s connected in series |
| Answer» A. Two SCR’s connected in reverse parallel | |
| 143. |
An SCR can be used |
| A. | as static conductor |
| B. | for power control |
| C. | for speed control of dc shunt motor |
| D. | all of these |
| Answer» D. all of these | |
| 144. |
A crowbar is a circuit which is used to protect a |
| A. | voltage sensitive load from excessive dc power supply output voltages |
| B. | current sensitive load from excessive dc power supply output voltages |
| C. | voltage sensitive load from excessive ac power supply output voltages |
| D. | current sensitive load from excessive ac power supply output voltages |
| Answer» A. voltage sensitive load from excessive dc power supply output voltages | |
| 145. |
The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is |
| A. | Sine wave |
| B. | Square wave |
| C. | Saw – tooth wave |
| D. | Trapezoidal wave |
| Answer» B. Square wave | |
| 146. |
The advantage of using free – wheeling diode in half controlled bridge converter is that |
| A. | There is always a path for the dc current independent of the ac line |
| B. | There is always a path for the ac current independent of the ac line |
| C. | There is always a path for the dc current dependent of the ac line |
| D. | There is always a path for the ac current independent of the ac line |
| Answer» A. There is always a path for the dc current independent of the ac line | |
| 147. |
Harmonics in 3 phase inverters can be reduced by using |
| A. | Passive filter |
| B. | Active filter |
| C. | Both passive and active filters |
| D. | None of these |
| Answer» C. Both passive and active filters | |
| 148. |
The most suited gate pulses given to the AC regulator with R – L load can be in the form of |
| A. | Continuous signal |
| B. | Large isolating pulse transformer |
| C. | A train of pulses |
| D. | None of these |
| Answer» C. A train of pulses | |
| 149. |
With increase in firing angle, |
| A. | Both harmonic distortion and quality of input current increases |
| B. | Harmonic distortion increases and quality of input current decreases |
| C. | Harmonic distortion decreases and quality of input current increases |
| D. | Both harmonic distortion and quality of input current decreases |
| Answer» B. Harmonic distortion increases and quality of input current decreases | |
| 150. |
The power MOSFET device is a |
| A. | Current controlled unipolar device |
| B. | Voltage controlled unipolar device |
| C. | Current controlled bipolar device |
| D. | Voltage controlled bipolar device |
| Answer» B. Voltage controlled unipolar device | |
Done Studing? Take A Test.
Great job completing your study session! Now it's time to put your knowledge to the test. Challenge yourself, see how much you've learned, and identify areas for improvement. Don’t worry, this is all part of the journey to mastery. Ready for the next step? Take a quiz to solidify what you've just studied.