Explore topic-wise MCQs in Electronics & Communication Engineering.

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.

1.

The accuracy of measurement by ohmmeter is very good.

A. True
B. False
Answer» C.
Discussion
2.

The moving iron instruments are generally repulsion type.

A. True
B. False
Answer» B. False
Discussion
3.

Assertion (A): Many instruments use eddy current damping.Reason (R): Eddy currents set up a magnetic flux which opposes the original movement which generates them.

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
Discussion
4.

The angle δ for a mica capacitor is about

A. 25°
B. 15°
C. 5°
D. 1°
Answer» E.
Discussion
5.

A meter has a square law scale. For 2 A current the deflection in 90°. For a deflection of 45°, the current is

A. 1 A
B. 1.5 A
C. 1.414 A
D. 1.61 A
Answer» D. 1.61 A
Discussion
6.

Two voltmeters 0-250 V each having resistances of 5 kΩ and 10 kΩ respectively and are connected in series. To ensure that neither of them goes beyond scale the total voltage which can be applied should be less than

A. 500 V
B. 400 V
C. 375 V
D. 250 V
Answer» D. 250 V
Discussion
7.

Two ammeters having resistances of 0.5 Ω and 0.25 Ω and having full scale reading of 25 A each are connected in parallel. To ensure that neither of them goes beyond scale, the total current should not be more than

A. 50 A
B. 37.5 A
C. 25 A
D. 40 A
Answer» C. 25 A
Discussion
8.

A 0-200 V voltmeter has a sensitivity of 1 kΩ per volt. The resistance of voltmeter is

A. 1 kΩ
B. 200 kΩ
C. 100 kΩ
D. 50 kΩ
Answer» C. 100 kΩ
Discussion
9.

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
Discussion
10.

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
Discussion
11.

Two voltmeters are each 0-300 V range. Their internal resistances are 10 kΩ and 20 kΩ They are connected is series and a voltage of 400 V is applied. Their readings respectively will be

A. 266.6 and 133.3 V
B. 133.3 and 266.6 V
C. 200 V each
D. 100 and 300 V
Answer» C. 200 V each
Discussion
12.

The ac bridge in figure is balanced. Z1 = 100∠30°, Z2 = 150∠0°, Z3 = 250∠ - 40° Then Z4 =

A. 375∠70° Ω
B. 375∠ - 70° Ω
C. 150∠0° Ω
D. 150∠20° Ω
Answer» C. 150∠0° Ω
Discussion
13.

A 300 V voltmeter has an accuracy of ± 2% of full scale deflection. When the reading is 222 V, the actual voltage

A. lies between 217.56 and 226.44 V
B. lies between 217.4 and 226.6 V
C. lies between 216 and 228 V
D. is exact 222 V
Answer» D. is exact 222 V
Discussion
14.

It is required to measure temperature in the range of 1300-1520°C. The most suitable thermocouple is

A. chromel constantan
B. iron constantan
C. chromel aluminium
D. platinum-rhodium
Answer» E.
Discussion
15.

In figure, Za = 100∠50°, Zb = 300∠-90° and Zc = 200∠0°. For balanced condition, Zd will be

A. 600∠ - 40°
B. 600∠140°
C. 600∠ - 140°
D. 150∠140°
Answer» D. 150∠140°
Discussion
16.

In figure, C0 is distributed capacitance and C is tuning capacitor. If C = C1 for fundamental frequency and C = C2 for second harmonic, then C0 =

A. [A].
B. [B].
C. [C].
D. C1 - 2C2
Answer» C. [C].
Discussion
17.

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 Ω
Discussion
18.

For measuring temperatures below 800°C with high accuracy, the best instrument is

A. optical pyrometer
B. thermistor based thermometer
C. GaAs junction diode thermometer
D. platinum resistance thermometer
Answer» E.
Discussion
19.

A 24 mm long conductor has a resistance of 128 Ω. The change in resistance is 13.3 Ω and change in length is 1.6 mm under tension. The gauge factor is

A. 1.2
B. 1.6
C. 2.1
D. 2.6
Answer» C. 2.1
Discussion
20.

The standard deviation σ in terms of n observations having deviations from mean dm can be written as

A. [A].
B. [B].
C. [C].
D. [D].
Answer» C. [C].
Discussion
21.

The time base of a high frequency CRO whose screen diameter is 10 cm is set at 10 μ sec/cm. The lowest frequency which can be fully displayed on the screen is

A. more than 100 kHz
B. equal to 100 kHz
C. equal to 10 kHz
D. less than 10 kHz
Answer» D. less than 10 kHz
Discussion
22.

A moving coil meter has 10 Ω resistance and requires 40 mA for full scale deflection. The shunt resistance required to convert it into 0-2 A ammeter is

A. 0.1021 Ω
B. 0.2041 Ω
C. 0.256 Ω
D. 0.4210 Ω
Answer» C. 0.256 Ω
Discussion
23.

An accelerometer has a seismic mass of 0.05 kg and spring constant of 3 x 105 N/m. If maximum displacement of mass is ± 1 mm, the maximum acceleration which can be measured is

A. 30 m/s2
B. 60 m/s2
C. 90 m/s2
D. 120 m/s2
Answer» C. 90 m/s2
Discussion
24.

In figure the values of Rx and Cx are

A. [A].
B. [B].
C. [C].
D. [D].
Answer» B. [B].
Discussion
25.

A wire strain gauge has a gauge factor of 2, resistance of 125 Ω and length 1 m. If length of wire changes by .005 m, change in resistance will be

A. 0.25 Ω
B. 0.5 Ω
C. 1.25 Ω
D. 2.5 Ω
Answer» D. 2.5 Ω
Discussion
26.

Two resistance R1 and R2 are connected in series R1 = 528 ± 5 Ω and R2 = 325 ± 3Ω. The total resistance will be

A. 853 ± 2 Ω
B. 853 ± 5 Ω
C. 853 ± 3 Ω
D. 853 ± 8 Ω
Answer» E.
Discussion
27.

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 Ω
Discussion
28.

The dead zone in a pyrometer is 0.125% of span. The calibration is 400°C to 1000°C. What temperature change might occur before it is detected.

A. 0.125°C
B. 0.75°C
C. 0.4°C
D. 1°C
Answer» C. 0.4°C
Discussion
29.

Four voltmeters have following specifications. If accuracy is main consideration which is the best?

A. 100 V, 2 mA
B. 100 V, 100 mA
C. 100 V, 1 mA
D. 100 V, 0.1 mA
Answer» E.
Discussion
30.

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.
Discussion
31.

A single element strain gauge bridge has two fixed resistances R1 and R1 of 120 Ω each and a variable resistance which gives full deflection at 120 Ω for zero strain and 120.6 Ω for straine e. If gauge factor is 2, strain e is

A. 0.0025
B. 0.0035
C. 0.005
D. 0.0075
Answer» B. 0.0035
Discussion
32.

An oscilloscope has an input impedance consisting of 1 MΩ and 20 pF is parallel. A high impedance probe connected to input of this oscilloscope has a 10 MΩ series resistance. This 10 MΩ series resistance

A. may not be shunted
B. should be shunted by 2 pF capacitor
C. should be shunted by 20 pF capacitor
D. should be shunted by 200 pF capacitor
Answer» C. should be shunted by 20 pF capacitor
Discussion
33.

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 (ωt + 45°)
Discussion
34.

A full wave rectifier type meter is used to measure the wave shape shown in figure. The voltmeter is calibrated to read rms value of sine wave. The reading of voltmeter will be

A. [A].
B. [B].
C. 100 V
D. 111 V
Answer» E.
Discussion
35.

A moving coil meter has a shunt of 0.02 Ω resistance. If coil resistance is 1000 Ω and a potential difference of 500 mV is required across it to cause full scale deflection, the current through shunt is

A. 2.5 A
B. 25 A
C. 0.25 A
D. 0.025 A
Answer» C. 0.25 A
Discussion
36.

A meter having 0-1000 μA range and 1000 Ω resistance is required to be changed to 0-100 mA meter. The value of shunt resistance is about

A. 1 Ω
B. 10 Ω
C. 99 Ω
D. 100 Ω
Answer» C. 99 Ω
Discussion
37.

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
Discussion
38.

The circuit of figure is used to measure the value Rx. Ammeter resistance Ra = 0.1 Ω voltmeter resistance Rv = 5000 Ω. It Rx1 and Rx2, are the measured values of Rx with switch in position 1 and 2, the mean of Rx1, and Rx2, is

A. 9.98 Ω
B. 10 Ω
C. 10.04 Ω
D. 10.1 Ω
Answer» D. 10.1 Ω
Discussion
39.

In a moving iron voltmeter the coil has a resistance of 20 Ω and an inductance of 0.3 H. The swamping resistance in 2000 Ω. To ensure correct reading with dc as well as 50 Hz ac, the value of capacitor to be connected in parallel with swamping resistance should be

A. 0.0125 μF
B. 0.0311 μF
C. 0.0521 μF
D. 0.0622 μF
Answer» C. 0.0521 μF
Discussion
40.

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.
Discussion
41.

Figure shows a Wheatstone bridge with RTD to one arm. If resistance of RTD = 1020 Ω, the voltage V0 is

A. 49 mV
B. 51 mV
C. 48 mV
D. 45 mV
Answer» B. 51 mV
Discussion
42.

A radiation thermometer is suitable for temperatures

A. below 500°C
B. below 100°C
C. above 500°C
D. above 1400°C
Answer» E.
Discussion
43.

In a platinum RTD, the change in resistance for a temperature rise of 50° C is about

A. 2%
B. 10%
C. 20%
D. 40%
Answer» D. 40%
Discussion
44.

If temperature increases by about 50°, the resistance of thermistor changes to

A. half of its initial value
B. twice of its initial value
C. eight times of its initial value
D. one eight of its initial value
Answer» E.
Discussion
45.

If two time varying signals of equal magnitudes and 90° phase displacement are applied to X and Y plates of CRO, the display will be

A. a straight line
B. a circle
C. an ellipse
D. a rectangle
Answer» C. an ellipse
Discussion
46.

In a dynamometer 3 phase power factor meter, the planes of the two moving coils are at

A. 60°
B. 0°
C. 120°
D. 90°
Answer» D. 90°
Discussion
47.

If the current in a capacitor leads the voltage by 80°, the loss angle of capacitor is

A. 80°
B. 10°
C. 100°
D. 170°
Answer» C. 100°
Discussion
48.

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%
Discussion
49.

In household energy meters the flux of series magnet is in phase with current but the flux of shunt magnet lags the voltage by 88°. The reading of energy meters

A. will be correct
B. will have a negative error
C. will have a positive error
D. may have positive or negative error
Answer» C. will have a positive error
Discussion
50.

If φsh is flux of shunt magnet, φse is flux of series magnet, ish is eddy current due to φse, the torque in an induction wattmeter is proportional to

A. φse ise + φsh ish
B. φsh ise - φse ish
C. φsh ish - φse ise
D. φsh ish + φse ise
Answer» C. φsh ish - φse ise
Discussion