MCQOPTIONS
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MCQOPTIONS
This section includes 571 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 551. |
The Lissajous pattern observed on screen of CRO is a straight line inclined at 45° to x axis. If X-plate input is 2 sin ωt, the Y-plate input is |
| A. | 2 sin ωt |
| B. | 2 sin (ωt + 45°) |
| C. | 2 sin (ωt - 45°) |
| D. | 22 sin ωt + 45°) |
| Answer» B. 2 sin (œât + 45¬∞) | |
| 552. |
The output of a Piezoelectric crystal has |
| A. | low amplitude and low impedance |
| B. | high amplitude and low impedance |
| C. | low amplitude and high impedance |
| D. | high amplitude and high impedance |
| Answer» D. high amplitude and high impedance | |
| 553. |
Which of the following measurements using a dc potentiometer do not require standardisation of potentiometer? |
| A. | Measurement of unknown voltage |
| B. | Measurement of resistance |
| C. | Measurement of unknown current |
| D. | Calibration of voltmeter |
| Answer» C. Measurement of unknown current | |
| 554. |
The current in a circuit is measured using a 150 : 1 CT If the ammeter reads 0.6 A, the circuit current is |
| A. | 250 A |
| B. | 90 A |
| C. | 156 A |
| D. | 144 A |
| Answer» C. 156 A | |
| 555. |
In figure, Z1 = 200∠60° Ω, Z2 = 400∠ - 90° Ω, Z3 = 300∠0°. Then Z4 for bridge to be balanced is |
| A. | 150∠30° Ω |
| B. | 400∠ - 90° Ω |
| C. | 300∠90° Ω |
| D. | 600∠ - 150° Ω |
| Answer» E. | |
| 556. |
Which of the following are needed both for protection and metering? |
| A. | Wattmeters |
| B. | Instrument transformers |
| C. | Energy meters |
| D. | Power factor meters |
| Answer» C. Energy meters | |
| 557. |
The Y plates of a CRO are excited by a voltage 2 sin 100 t and the X plates are not connected. The display would be |
| A. | a vertical line |
| B. | a horizontal line |
| C. | sine wave |
| D. | slant line |
| Answer» B. a horizontal line | |
| 558. |
A dynamometer wattmeter is connected in ac circuit. The measured power is |
| A. | rms power |
| B. | average power |
| C. | peak power |
| D. | instantaneous power |
| Answer» C. peak power | |
| 559. |
An ammeter of 0-25 A range has a guaranteed accuracy of 1% of full scale reading. The current measured is 5 A. The limiting error is |
| A. | 0.02 |
| B. | 0.025 |
| C. | 0.04 |
| D. | 0.05 |
| Answer» E. | |
| 560. |
Assertion (A): CRO can be used to study waveshape accurately.Reason (R): Input impedance of a CRO is very high. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true R is false |
| D. | A is false R is true |
| Answer» B. Both A and R are true but R is not correct explanation of A | |
| 561. |
A moving coil instrument has a resistance of 0.6 Ω and full scale deflection at 0.1 A. To convert it into an ammeter of 0-15 A range, the resistance of shunt should be |
| A. | 0.6 Ω |
| B. | 0.06 Ω |
| C. | 0.1 Ω |
| D. | 0.004 Ω |
| Answer» E. | |
| 562. |
Kelvin's double bridge is used to measure low resistances because |
| A. | it has high sensitivity |
| B. | there is no thermoelectric emf |
| C. | resistance variation due to temperature |
| D. | effect of contact and lead resistances is eliminated |
| Answer» E. | |
| 563. |
In a CRO which of the following is not a part of electron gun |
| A. | cathode |
| B. | grid |
| C. | accelerating anode |
| D. | X - Y plates |
| Answer» E. | |
| 564. |
A direct current can be measured |
| A. | directly by dc potentiometer |
| B. | by dc potentiometer in conjunction with a standard resistance |
| C. | by dc potentiometer in conjunction with volt ratio box |
| D. | none of the above |
| Answer» C. by dc potentiometer in conjunction with volt ratio box | |
| 565. |
The coil of a moving iron instrument has a resistance of 500 Ω and an inductance of 1 H. It reads 250 V when a 250 V dc is applied. If series resistance is 2000 Ω, its reading when fed by 250 V, 50 Hz ac will be |
| A. | 260 V |
| B. | 252 V |
| C. | 250 V |
| D. | 248 V |
| Answer» E. | |
| 566. |
A 1 mA meter is to be converted to 1 A ammeter. The meter resistance is 100 Ω. The value of shunt resistance is |
| A. | 0.001 Ω |
| B. | 0.1001 Ω |
| C. | 100 Ω |
| D. | 1000 Ω |
| Answer» C. 100 Œ© | |
| 567. |
If reference sound pressure P0 is 2 x 10-5 N/m2, a sound pressure of 90 dB is equal to |
| A. | 0.632 N/m2 |
| B. | 0.707 N/m2 |
| C. | 0.835 N/m2 |
| D. | 0.925 N/m2 |
| Answer» B. 0.707 N/m2 | |
| 568. |
In 3 phase power measurement by two wattmeter method, the reading of one wattmeter is zero. The power factor of load is |
| A. | 1 |
| B. | 0.5 |
| C. | 0 |
| D. | 0.8 |
| Answer» C. 0 | |
| 569. |
Assertion (A): If the resistance of shunt of an ammeter is increased, the range of ammeter is reduced.Reason (R): If the series resistance of a voltmeter is increased, the range of voltmeter is increased. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true R is false |
| D. | A is false R is true |
| Answer» C. A is true R is false | |
| 570. |
Magnetic flux density has the dimensions |
| A. | MI-1T-2 |
| B. | M-1I-2T-2 |
| C. | ML-3T-2 |
| D. | MI-1T-3 |
| Answer» B. M-1I-2T-2 | |
| 571. |
To increase Q factor of a coil, the wire should be |
| A. | long |
| B. | thin |
| C. | thick |
| D. | long and thin |
| Answer» D. long and thin | |