Electrical Earthing MCQ

1. For proper earthing, what should be the maximum value of earth resistance while carrying out the testing of earth continuity path?

  1. 1 Ω
  2. 2 Ω
  3. 5 Ω
  4. 10 Ω
Answer. c

2. From the point of view of safety, the resistance of the earthing electrode should be

  1. Low
  2. High
  3. Medium
  4. The value of resistance of earth does not affect the safety
Answer. a

3. Materials used in plate earthing are

  1. Wood coal
  2. Salt, earthing plate
  3. (a) and (b) both
  4. None of the above
Answer. c

4. Minimum distance of underground cable from the foundation of a building should be

  1. 100 cm
  2. 50 cm
  3. 10 cm
  4. 5 cm
Answer. c

5. In house wiring, black and green wires indicate

  1. Earth and neutral respectively
  2. Phase and neutral respectively
  3. Phase and earth respectively
  4. Neutral and earth respectively
Answer. d

6. Earth resistance comprises of

  1. Resistance of soil away from electrode.
  2. Contact resistance between electrode and soil.
  3. Resistance of metal electrode
  1. 1 only
  2. 1 and 2 only
  3. 1 and 3 only
  4. 1 ,2 and 3 together
Answer. d

7. Humans are more vulnerable to electric shock current at?

  1. 50 Hz
  2. 48 Hz
  3. 40 Hz
  4. 45 Hz
Answer. a

8. The earth’s potential is taken as

  1. Infinite
  2. Supply voltage
  3. 1 volt
  4. Zero
Answer. d

9. For reducing tower footing resistance, it is better to use

  1. Chemical and ground rod only
  2. Chemical and counterpoise only
  3. Ground rod and counterpoise only
  4. None of these
Answer. c

10. The earthing electrodes should be placed within what distance in meters from the building whose installation system is being earthed

  1. 4
  2. 2.5
  3. 1.5
  4. 0.5
Answer. c

11. The purpose of earthing electric appliances is

  1. To provide safety against shock
  2. To ensure that the appliance saves current
  3. To ensure that the appliance gets full voltage
  4. None of these
Answer. c

12. Inside the earth pit, the earthing electrode should be placed

  1. Vertical
  2. Horizontal
  3. Inclined at 45°
  4. Inclined at any angle other than 45°
Answer. a

13. The acceptable value of grounding resistance to a domestic application is

  1. 0.1 Ω
  2. 1 Ω
  3. 10 Ω
  4. 100 Ω
Answer. b

14. For the measurement of the earth resistance of a given earth electrode

  1. collecting electrode should be very near to the electrode under test
  2. collecting electrode should touch the electrode under test
  3. collecting electrode should be far way the electrode under test
  4. none of these
Answer. c

15. The addition of ground rods in the earthing grid

  1. Decrease the earth resistance
  2. Has no effect on earth resistance
  3. Slightly decrease the earth resistance
  4. Slightly increase the earth resistance
Answer. c

16. The purpose of earthing electric appliances is

  1. To provide safety against shock
  2. To ensure that the appliances work properly
  3. To ensure that the appliances get full voltage
  4. None of the above
Answer. a

17. Normally the human body resistance in the totally wet and the dry condition is ____________ respectively.

  1. 1 kΩ and 1 MΩ
  2. 0.1 Ω and 10 kΩ
  3. 100 Ω and1 kΩ
  4. 100 Ω and 10 kΩ
Answer. a

18. Mixture preferred for filling around the earth electrode for effective earthing is

  1. Paper-salt mixture
  2. Saw dust mixture
  3. Coal-salt mixture
  4. Lime-sand mixture
Answer. c

19. The effect of electric shock on human body depends on:

  1. current
  2. voltage
  3. duration of contact
  1. only i
  2. only ii
  3. only iii
  4. all i, ii and iii
Answer. d

20. Which type of neutral grounding method has high transient voltages appear under fault conditions?

  1. Solid grounding
  2. Resistance grounding
  3. Reactance grounding
  4. Plate grounding
Answer. c

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