MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 227 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
n-channel FETs are superior to P-channel FETs, because |
| A. | They have higher input impedance |
| B. | They have high switching time |
| C. | They consume less power |
| D. | Mobility of electrons is greater than that of holes |
| Answer» E. | |
| 202. |
For a JFET, when VDS is increased beyond the pinch off voltage, the drain current |
| A. | Increases |
| B. | Decreases |
| C. | Remains constant |
| D. | First decreases and then increases |
| Answer» D. First decreases and then increases | |
| 203. |
which of the following statements are true about BJT? (i) It has more power handling capability than MOSFET (ii) Has higher switching speed than IGBT and MOSFET (iii) Has low on state conduction resistance (iv) Has second breakdown voltage problem |
| A. | All are true |
| B. | (i), (ii), (iii) and (iv) |
| C. | (i), (iii) and (iv) |
| D. | (ii), (iii) and (iv) |
| Answer» D. (ii), (iii) and (iv) | |
| 204. |
A three phase fully controlled thyristor bridge converter is used as line commutated inverter to feed 50 KW power at 420 V DC to a three phase 415V(line), 50Hz as mains. Consider Dc link current to be constant. The rms current of the thyristor is [GATE2007] |
| A. | 119.05A |
| B. | 79.37A |
| C. | 68.73A |
| D. | 39.68A |
| Answer» E. | |
| 205. |
A single phase fully controlled thyristor bridge ac-dc converter is operating at a firing angle of 25 degree, and an overlap angle 10 degree with constant dc output current of 20A. The fundamental power factor ( displacement factor) at input ac mains is [GATE2007] |
| A. | 0.78 |
| B. | 0.827 |
| C. | 0.866 |
| D. | 0.9 |
| Answer» B. 0.827 | |
| 206. |
Circuit turn-off time of an SCR is defined as the time [GATE2011] |
| A. | taken by the SCR to turn off |
| B. | required for SCR current to become zero |
| C. | for which the SCR is reverse biased by the commutation circuit |
| D. | for which the SCR is reverse biased to reduce its current below the holding current |
| Answer» D. for which the SCR is reverse biased to reduce its current below the holding current | |
| 207. |
The minimum approximate volt-second rating of the pulse transformer suitable for triggering the SCR should be: ( volt-second rating is the maximum of product of the voltage and the width of the pulse that may be applied |
| A. | 2000 uV-s |
| B. | 200 uV-s |
| C. | 20 uV-s |
| D. | 2.0 uV-s |
| Answer» B. 200 uV-s | |
| 208. |
The resistance R should be |
| A. | 4.7K Ohm |
| B. | 470 Ohm |
| C. | 47 Ohm |
| D. | 4.7 Ohm |
| Answer» D. 4.7 Ohm | |
| 209. |
If the dc bus voltage Vd = 300v, the power consumed by 3 phase load is [GATE -2011] |
| A. | 1.5kW |
| B. | 2.0 kW |
| C. | 2.5 kW |
| D. | 3.0 kW |
| Answer» E. | |
| 210. |
The rms value of load phase voltage is [GATE -2011] |
| A. | 106.1V |
| B. | . 141.4 V |
| C. | 212.2 V |
| D. | 282.8V |
| Answer» C. 212.2 V | |
| 211. |
The typical ratio of latching current to holding current in a 20A thyristor is [GATE -2011] |
| A. | 5.0 |
| B. | 2.0 |
| C. | 1.0 |
| D. | . 0.5 |
| Answer» C. 1.0 | |
| 212. |
The average output voltage(Vdc) of the full wave diode bridge rectifier is |
| A. | Vm/2 |
| B. | 2Vm/pi |
| C. | 3Vm/pi |
| D. | 4Vm/pi |
| Answer» C. 3Vm/pi | |
| 213. |
A source follower using an FET usually has a voltage gain which is |
| A. | Greater than +100 |
| B. | Slightly less than unity but positive |
| C. | Exactly unity but negative |
| D. | About -10 |
| Answer» B. Slightly less than unity but positive | |
| 214. |
The main disadvantage of voltage doubler power supply circuit is |
| A. | Excessive current |
| B. | Excessive voltage |
| C. | Insufficient rectification |
| D. | Poor regulation under heavy loads |
| Answer» E. | |
| 215. |
If a full wave bridge circuit is used with a transformer whose secondary provides 50Vrms, the peak voltage that occurs across the diodes in the reverse direction is approximately |
| A. | 50 Vpk |
| B. | 70 Vpk |
| C. | 100 Vpk |
| D. | 140 Vpk |
| Answer» C. 100 Vpk | |
| 216. |
If a half wave rectifier is used with 165Vpk AC input, the effective dc output voltage is |
| A. | considerably less than 165V |
| B. | slightly less than 165V |
| C. | exactly 165V |
| D. | slightly more than 165V |
| Answer» B. slightly less than 165V | |
| 217. |
The best rectifier circuit for the power supply designed to provide high power at low voltage is |
| A. | half wave arrangement |
| B. | full wave, center tap arrangement |
| C. | quarter wave arrangement |
| D. | voltage doubler arrangement |
| Answer» C. quarter wave arrangement | |
| 218. |
An advantage of full wave bridge rectification is |
| A. | it uses the whole transformer secondary for the entire ac input cycle |
| B. | it costs less than other rectifier types |
| C. | it cuts off half of the ac wave cycle |
| D. | it never needs a filter |
| Answer» B. it costs less than other rectifier types | |
| 219. |
The output of a rectifier circuit without filter is |
| A. | 50 Hz AC |
| B. | smooth DC |
| C. | pulsating DC |
| D. | 60 hz AC |
| Answer» D. 60 hz AC | |
| 220. |
In a full-wave rectifier using two ideal diodes,Vdc & Vm are the dc & peak values of the voltage respectively across a resistive loaD. If PIV is the peak inverse voltage of the diode,then the appropriate relationships for the rectifier is |
| A. | Vdc=Vm/π,PIV=2Vm |
| B. | Vdc=2Vm/π,PIV=2Vm |
| C. | Vdc=2Vm/π,PIV=Vm |
| D. | Vdc=Vm/π,PIV=Vm |
| Answer» C. Vdc=2Vm/π,PIV=Vm | |
| 221. |
Thermal runaway is not possible in FET because as the temperature of FET increases |
| A. | The mobility decreases |
| B. | The transconductance increases |
| C. | The drain current increases |
| D. | None of the above |
| Answer» B. The transconductance increases | |
| 222. |
A 240V, 50Hz supply feeds a highly inductive load of 50 Ohm resistance through a thyristor full control bridge. when the firing angle α= 45°, load power is |
| A. | 456 W |
| B. | 466 W |
| C. | 732 W |
| D. | 120 W |
| Answer» C. 732 W | |
| 223. |
A D.C. to D.C. chopper operates from a 48 V source with a resistive load of 24Ohm. The chopper frequency is 250Hz. When Ton= 3 ms, the rms current is |
| A. | 1.5A |
| B. | 15mA |
| C. | 1.73A |
| D. | 173mA |
| Answer» D. 173mA | |
| 224. |
A full-wave fully controlled bridge has a highly inductive load with a resistance of 55 Ohm, and a supply of 110V at 50Hz. The value of load power for a firing angle α=75° is |
| A. | 10W |
| B. | 11W |
| C. | 10.5W |
| D. | 10.9W |
| Answer» E. | |
| 225. |
A thyristor half wave controlled converter has a supply voltage of 240V at 50Hz and a load resistance of 100 Ohm. when the firing delay angle is 30 the average value of load current is |
| A. | 126A |
| B. | 2.4A |
| C. | 126mA |
| D. | 24 A |
| Answer» D. 24 A | |
| 226. |
A D.C. to D.C. chopper operates from a 48 V battery source into a resistive load of 24Ohm. The frequency of the chopper is set to 250Hz. When chopper on-time is 1 ms the load power is |
| A. | 6W |
| B. | 12W |
| C. | 24W |
| D. | 48W |
| Answer» D. 48W | |
| 227. |
A 240V, 50Hz supply feeds a highly inductive load of 50 Ohm resistance through a half controlled thyristor bridge. When the firing angle α=45°, the load power is |
| A. | 418 W |
| B. | 512 W |
| C. | 367 W |
| D. | 128 W |
| Answer» C. 367 W | |