Earthing and Grounding MCQs

1.What is the primary purpose of grounding in LV electrical installations? 

A) Voltage control
B) Equipment cooling
C) Personnel safety and equipment protection
D) Power factor correction storage

ANSWER= (C) Personnel safety and equipment protection
Explaination:- Grounding protects personnel from electric shock and safeguards equipment from overvoltage and fault currents.
Check Answer

 

2. A grounding design shows multiple electrodes in a grid pattern connected with copper strips. What is this system called?

A) Ring earthing
B) Step earthing
C) Mesh or Grid earthing
D) Strip earthing

ANSWER= (C) Mesh or Grid earthing
Explaination:- Grid (mesh) earthing is common in substations and high-rise buildings for uniform potential.
Check Answer

 

3. If a transformer has delta-star winding, grounding is usually done at:

A) Delta point
B) Star point (neutral)
C) Both of them
D) None of them

ANSWER= (B) Star point
Explaination:- Grounding is typically done at the star point of transformer secondary for neutral reference. 
Check Answer

 

4.In a TN-C system, what is a major drawback?

A) No fault detection
B) Risk of PEN conductor break
C) Requires multiple earth rod
D) Cannot be used in LV 

ANSWER= (B) Risk of PEN conductor break 
Explaination:- If the PEN conductor breaks, exposed parts can become live, a serious safety hazard. 
Check Answer

5. Which device is used to measure earth resistance directly?

A) Megger
B) Thermostat
C) Multimeter
D) Earth tester

ANSWER= (D) Earth tester
Explaination:- An earth tester is a dedicated instrument for measuring earth resistance.
Check Answer

 

6.Which of these is not a component of an earthing system?

A) Earth electrode
B) Earth mat
C) Foundation
D) Earth conductor

ANSWER= (C) Foundation
Explaination:- Foundation is a structural element, not a grounding component.
Check Answer

 

7. Which of the following standards in India provides detailed guidance on earthing?

A) IS 732
B) IS 3043
C) IS 1554
D) IEC 60947

ANSWER= (B) IS 3043
Explaination:- IS 3043: Code of Practice for Earthing is the primary standard for grounding in India.
Check Answer

 

8.Which of the following earthing types is used in high-rise commercial buildings in India?

A) TN-S or TN-C-S with earth mat
B) TT system
C) IT system
D) none of above

ANSWER= (A) TN-S or TN-C-S with earth mat
Explaination:- TN-C-S is common in commercial buildings with proper earthing grid.
Check Answer

 

9.What should be the minimum separation between two earth pits to avoid mutual interference?

 A) 1 meter
 B) 3 meters
 C) 5 meters
 D) Twice the length of the electrode

 ANSWER= (B) Twice the length of the electrode 
Explaination:- To prevent mutual interference, spacing = 2 × length of electrode is a rule of thumb.
Check Answer

 

10. In an offshore oil and gas installation, which type of earthing system is preferred?

 A) IT System
 B) TT System
 C) TN-CS System
 D) TN-S System

ANSWER= (A) IT System
Explaination:- Offshore platforms prefer isolated (IT) systems for enhanced safety and fault detection.
Check Answer 

11.In a TN-C-S system, where should the main earth electrode be connected?

 A)  Only at the consumer side
 B) At transformer and consumer ends
 C) Only at the neutral terminal
 D) Not required

 ANSWER= (B) At transformer and consumer ends
Explaination:- For TN-C-S, electrodes should be installed both at the supply and consumer end for equipotential bonding.
Check Answer

 

12. Which of the following factors does not influence the resistance of an earth electrode?

 A) Soil resistivity
 B) Number of rods
 C) Diameter of rod
 D) Type of load connected

ANSWER= (D) Type of load connected
Explaination:- Earth resistance depends on physical factors like soil and electrode configuration, not on the load type.
Check Answer

 

13.Which is a true statement for grounding conductors?

 A) Must have insulation
 B) Can be aluminum in any case
 C) Should have low resistance
 D) Must be buried in concrete

ANSWER= (C) Should have low resistance
Explaination:- Grounding conductors should have low resistance to ensure effective fault current path.