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.
| 451. |
To measure an emf by dc potentiometer it is necessary to standardise the potentiometer with the help of a standard cell. |
| A. | 1 |
| B. | |
| C. | Current transformer |
| D. | Potential transformer |
| Answer» B. | |
| 452. |
The resistance of a 125 Ω strain gauge changes by 1 ohm for 4000 micro strain. The gauge factor is |
| A. | 1.5 |
| B. | 2 |
| C. | 2.5 |
| D. | 3 |
| Answer» C. 2.5 | |
| 453. |
Two ammeters A and B both 0-10 A have internal resistance of 1 Ω and 0.5 Ω respectively. They are connected in parallel. If total current is 15 A, then |
| A. | IA = IB = 7.5 A |
| B. | IA = 5 A, IB = 10 A |
| C. | IA = 10 A, IB = 5 A |
| D. | IA = 9 A, IB = 6 A |
| Answer» C. IA = 10 A, IB = 5 A | |
| 454. |
A permanent magnet moving coil measures |
| A. | true rms value |
| B. | dc value |
| C. | peak value |
| D. | rms plus dc value |
| Answer» C. peak value | |
| 455. |
Which of the following is true about an impulse voltage? |
| A. | It is a unidirectional voltage |
| B. | Chopped impulse flashover does not occur |
| C. | Time taken to rise is equal to time taken to fall |
| D. | RMS value is always less than 50% of average value |
| Answer» B. Chopped impulse flashover does not occur | |
| 456. |
When deflecting torque and braking torque in an energy meter are zero, |
| A. | the disc rotates at steady speed |
| B. | the disc is stationary |
| C. | the disc accelerates |
| D. | the disc retards |
| Answer» B. the disc is stationary | |
| 457. |
Loss of charge method is suitable for medium resistances. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 458. |
In a ballistic galvanometer, a charge of 100 μC gives a first swing of 25°. The charge required to cause first swing of 50° is |
| A. | 200 μC |
| B. | 400 μC |
| C. | 50 μC |
| D. | 25 μC |
| Answer» C. 50 ŒºC | |
| 459. |
The current through a resistance R is shown in figure. The computed value of power is |
| A. | 400 ± 0.42 W |
| B. | 400 ± 4.6 W |
| C. | 400 ± 8.85 W |
| D. | 400 ± 10.65 W |
| Answer» D. 400 ¬± 10.65 W | |
| 460. |
The D'Arsonval- movement can be converted into audio frequency ac ammeter by adding a |
| A. | thermocouple |
| B. | transducer |
| C. | chopper |
| D. | rectifier |
| Answer» E. | |
| 461. |
Assertion (A): A photovoltaic cell is greatly affected by temperature.Reason (R): Both germanium and silicon can be used for photovoltaic cells. |
| 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 | |
| 462. |
Assertion (A): Thermocouple instruments can be used for ac only. Reason (R): Thermocouple instrument has a non linear scale. |
| 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» E. | |
| 463. |
Assertion (A): Thermistors are commonly used to measure hot spot temperatures in electric machines.Reason (R): Thermistor has the advantages of high temperature coefficient, small size and high speed of response. |
| 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 | |
| 464. |
Two sinusoidal signals of equal amplitude and frequency are applied to X and Y plate of CRO respectively. The observed Lissajous pattern is a straight line. The phase shift between signals is |
| A. | zero |
| B. | 90° |
| C. | either zero or 180° |
| D. | either 90° or 270° |
| Answer» D. either 90¬∞ or 270¬∞ | |
| 465. |
Burden of an instrument transformer is expressed in |
| A. | A |
| B. | V-A |
| C. | Ω |
| D. | watt |
| Answer» C. Œ© | |
| 466. |
In a CRO, the time base signal is applied to |
| A. | X plates |
| B. | Y plates |
| C. | either X or Y plates |
| D. | alternately X and Y plates |
| Answer» B. Y plates | |
| 467. |
Three phase four wire induction energy meter is used to measure |
| A. | energy in 3 phase balanced star load |
| B. | energy in 3 phase balanced delta load |
| C. | energy in 3 phase unbalanced load |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 468. |
The deflection of a DArsonval galvanometer is measured through a mirror and scale. The mirror is 1 m away from the light source. The mirror is mounted on, the moving system. If mirror rotates through 0.2 rad the displacement on the scale is |
| A. | 0.2 m |
| B. | 0.4 m |
| C. | 0.1 m |
| D. | 0.05 m |
| Answer» C. 0.1 m | |
| 469. |
The torque in induction wattmeters due to |
| A. | capacitive current |
| B. | electrostatic effect |
| C. | hall effect |
| D. | eddy currents |
| Answer» E. | |
| 470. |
If C is spring constant and θ is deflection, controlling torque is |
| A. | Cθ |
| B. | C/θ |
| C. | θ/C |
| D. | C2θ |
| Answer» B. C/Œ∏ | |
| 471. |
Which of the following voltmeters would you use for measuring voltage across 20 kΩ resistance? |
| A. | Voltmeter having a resistance of 5 kΩ |
| B. | Voltmeter having a sensitivity of 1 kW/V |
| C. | Voltmeter having sensitivity of 10 kW/V |
| D. | None of the above |
| Answer» D. None of the above | |
| 472. |
Two resistors R1 = 36 Ω ± 5% and R2 = 75 Ω ± 5% are connected in series. The total resistance is |
| A. | 111 ± 0 Ω |
| B. | 111 ± 2.778 Ω |
| C. | 111 ± 5.55 Ω |
| D. | 111 ± 7.23 Ω |
| Answer» D. 111 ¬± 7.23 Œ© | |
| 473. |
Electrostatic voltmeter is suitable only for low voltages. |
| A. | 1 |
| B. | |
| C. | 30 m/s2 |
| D. | 60 m/s2 |
| Answer» C. 30 m/s2 | |
| 474. |
Consider the following statements: In a differential amplifier using JFET, the differential output offset is due to mismatch between FET parametersdifference in values of resistances used in circuitvariation in supply voltage. Of the statements, the correct statements are |
| A. | 1 and 2 |
| B. | 1, 2, 3 |
| C. | 2, 3 |
| D. | 1, 3 |
| Answer» B. 1, 2, 3 | |
| 475. |
Magnetic deflection is inversely proportional to |
| A. | voltage |
| B. | (voltage)0.5 |
| C. | (voltage)1.5 |
| D. | (voltage)2 |
| Answer» C. (voltage)1.5 | |
| 476. |
In low power factor wattmeter, the pressure coil is connected |
| A. | to the supply side of current coil |
| B. | to the load side of current coil |
| C. | in either (a) or (b) |
| D. | across the mains |
| Answer» C. in either (a) or (b) | |
| 477. |
The speed transducer using a drag cup rotor has the main advantage of |
| A. | very high accuracy |
| B. | low energy requirement |
| C. | cheap construction |
| D. | all of the above |
| Answer» C. cheap construction | |
| 478. |
A current of 3.25 A is flowing through a resistance of 34.98 Ω. The voltage drop across resistance to the appropriate number of significant figures is |
| A. | 113.685 V |
| B. | 113.68 V |
| C. | 113.6 V |
| D. | 114 V |
| Answer» E. | |
| 479. |
In two wattmeter method of 3 phase power measurement, when does one wattmeter read negative |
| A. | when power factor is less than 0.5 lagging |
| B. | when power factor is greater than 0.5 lagging |
| C. | when power factor is less than 0.5 |
| D. | when power factor is unity |
| Answer» D. when power factor is unity | |
| 480. |
The accuracy of a multimeter is about |
| A. | ± 0.5% |
| B. | ± 3% |
| C. | ± 0.01% |
| D. | ± 10% |
| Answer» C. ¬± 0.01% | |
| 481. |
In figure, the position of voltmeter and ammeter are exchanged. It may result in damage to |
| A. | both the instruments |
| B. | ammeter |
| C. | voltmeter |
| D. | neither of two |
| Answer» C. voltmeter | |
| 482. |
If M is mutual inductance between fixed and moving coils and θ is deflection of dynamometer instrument, then |
| A. | |
| B. | θ ∝ M |
| Answer» B. Œ∏ ‚àù M | |
| 483. |
Assertion (A): The trigger circuit of a CRO is excited by the same signal as Y plates.Reason (R): The time base generator develops a saw tooth voltage. |
| 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 | |
| 484. |
Assertion (A): A 3 phase wattmeter consists of two wattmeters mounted in one case.Reason (R): Power measurement in a 3 phase circuit can be conveniently done by two wattmeter method. |
| 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 | |
| 485. |
The resistance of voltmeter affects the accuracy of measurement in loss of charge method. |
| A. | 1 |
| B. | |
| C. | peak value of ac current |
| D. | average value of ac current |
| Answer» B. | |
| 486. |
In a resistance strain gauge, G = 2, stress = 1050 kg/cm2, R = 1000 Ω. The value of ΔR will be |
| A. | 2 Ω |
| B. | 3 Ω |
| C. | 4 Ω |
| D. | 1 Ω |
| Answer» E. | |
| 487. |
As per BIS there are 6 accuracy classes of instruments. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 488. |
If Eb is the potential of accelerating anode, the energy of electrons as they emerge from electron gun is proportional to |
| A. | Eb |
| B. | Eb |
| C. | Eb1.5 |
| D. | Eb2 |
| Answer» C. Eb1.5 | |
| 489. |
Consider the following features of an instrument suitable for both ac and dcfree from hysteresis and eddy current errorsNo waveform and frequency errorsit is essentially a voltmeter This instrument is |
| A. | moving iron |
| B. | moving coil |
| C. | electrostatic |
| D. | dynamometer |
| Answer» D. dynamometer | |
| 490. |
It is required to measure pressure using LVDT. The additional device needed is |
| A. | strain gauge |
| B. | pitot tube |
| C. | bourden tube |
| D. | rotameter |
| Answer» D. rotameter | |
| 491. |
Absolute instruments are used in |
| A. | laboratories |
| B. | industries |
| C. | power houses |
| D. | standard laboratories |
| Answer» E. | |
| 492. |
The scale of dynamometer wattmeter is non linear. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 493. |
Which bridge can be used to measure frequency? |
| A. | Maxwell |
| B. | Kelvin |
| C. | Schering |
| D. | Wein |
| Answer» E. | |
| 494. |
The range of RTD using platinum is about |
| A. | -100° C to 700°C |
| B. | -200°C to 1000°C |
| C. | 100°C to 1000°C |
| D. | about 500°C |
| Answer» B. -200¬∞C to 1000¬∞C | |
| 495. |
In a thermocouple temperature transducer, the output voltage is usually measured by |
| A. | high resistance ammeter |
| B. | high resistance voltmeter |
| C. | high resistance milli-voltmeter |
| D. | none of the above |
| Answer» D. none of the above | |
| 496. |
The most commonly used moving iron instruments are |
| A. | repulsion type |
| B. | attraction type |
| C. | a combination of attraction and repulsion type |
| D. | none of the above |
| Answer» B. attraction type | |
| 497. |
If the load current is high, the pressure coil of wattmeter should be connected directly across the load. |
| A. | 1 |
| B. | |
| C. | measure magnitude of peak voltage |
| D. | measure frequency |
| Answer» B. | |
| 498. |
A resistance is measured by voltmeter-ammeter method. The voltmeter is 0-250V, ± 1% accuracy and ammeter is 0-5 A, ± 1 % accuracy. The readings of voltmeter and ammeter are 100 V and 2 A respectively. The error in the measured resistance can be |
| A. | ± 1% |
| B. | ± 2% |
| C. | ± 5% |
| D. | ± 10% |
| Answer» D. ¬± 10% | |
| 499. |
It is required to measure angular position. Out of the transducers Circular potentiometerLVDTE pick upSynchro The proper devices are |
| A. | 1, 2, 3, 4 |
| B. | 2 and 3 |
| C. | 1, 2, 4 |
| D. | 1 and 4 |
| Answer» E. | |
| 500. |
In a platinum RTD, the change in resistance for a temperature rise of 50° C is about |
| A. | 0.02 |
| B. | 0.1 |
| C. | 0.2 |
| D. | 0.4 |
| Answer» D. 0.4 | |