Class 11 Electronics Chapter 4 Electrical Earthing System

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Class 11 Electronics Chapter 4 Electrical Earthing System

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. AHSEC Class 11 Electronics Textual Solutions are part of All Subject Solutions. Here we have given AHSEC Class 11 Electronics Textbook Solutions English Medium for All Chapters, You can practice these here.

Electrical Earthing System

Chapter: 4

CHECK YOUR PROGRESS

A. Multiple choice questions:

1. What is the specification of GI earth plate? 

(a) 60 cm × 60 cm × 3 mm.

(b) 60 cm × 60 cm × 6 mm.

(c) 60 cm × 60 cm × 4 mm.

(d) 60 cm × 60 cm × 5 mm.

Ans: (a) 60 cm × 60 cm × 3 mm.

2. What is the amount of charcoal and salt needed for GI pipe earthing? 

(a) Charcoal 5 kg, salt 8 kg.

(b) Charcoal 10 kg, salt 8 kg. 

(c) Charcoal 10 kg, salt 10 kg. 

(d) Charcoal 5 kg, salt 5 kg.

Ans: (c) Charcoal 10 kg, salt 10 kg.

3. The size of the earth or ground wire is based on __________________. 

(a) The maximum fault current being carried through the ground wire.

(b) The rated current carrying capacity of the service line 

(c) Soil resistance.

(d) Both (a) and (c).

Ans: (d) Both (a) and (c).

4. Earth or ground wire is made of __________________.  

(a) Copper. 

(b) Aluminium. 

(c) Iron. 

(d) Galvanised steel.

Ans: (d) Galvanised steel.

5. Generally, grounding is provided for __________________. 

(a) The safety of the equipment. 

(b) The safety of the operating personnel. 

(c) Both (a) and (b).

(d) None of the above.

Ans: (c) Both (a) and (b).

6. Ground resistance should be designed such that __________________. 

(a) Grounding resistance is as low as possible. 

(b) Grounding resistance is as high as possible. 

(c) Grounding resistance is always zero. 

(d) None of the above.

Ans: (a) Grounding resistance is as low as possible.

7. The objective of earthing or grounding is __________________.  

(a) To provide as low resistance as possible to the ground. 

(b) To provide as high resistance as possible to the ground. 

(c) To provide flow of positive, negative and zero sequence currents. 

(d) None of the above.

Ans: (a) To provide as low resistance as possible to the ground.

8. Moisture content in the soil __________________ the earth’s soil resistance. 

(a) Increases. 

(b) Decreases. 

(c) Does not affect. 

(d) None of the above.

Ans: (b) Decreases.

9. Factors on which soil resistance depends is/are __________________. 

(a) Depth of the electrode.

(b) Moisture. 

(c) NaCl (salt). 

(d) All of the above. 

Ans: (d) All of the above.

10. What type of earthing is used by transmission lines? 

(a) Plate earthing. 

(b) Rod earthing.

(c) Strip earthing. 

(d) Both (a) and (c). 

Ans: (c) Strip earthing. 

11. Average resistance of human body is __________________. 

(a) 200 Ohm.

(b) 1000 Ohm. 

(c) 1500 Ohm. 

(d) 2000 Ohm.

Ans: (b) 1000 Ohm. 

12. Which type of earthing is also called ‘fire earthing’? 

(a) Plate earthing. 

(b) Rod earthing.

(c) Strip earthing. 

(d) All of the above.

Ans: (b) Rod earthing.

B. Fill in the blanks:

1. The algebraic sum of the resistances of earth continuity conductor, earthing lead, earth electrode and earth is called ________________. 

Ans: Earth resistance.

2. The _______________ protects a structure from damage by intercepting flashes of lightning and transmitting the current to the ground. 

Ans: Lightning arrestor.

3. The minimum distance between two earth electrodes must be ________________. 

Ans: 5 metre.

4. Collect all wires in a metallic pipe from the earth electrode. Make sure that the pipe is _______________ above the ground surface. 

Ans: 1 feet (30 cm).

5. Strip electrodes of cross section not less than ________________ are buried in horizontal trenches of a minimum depth of 0.5m.

Ans: 0.5m. 

C. State whether the following statements are True or False: 

1. Soil resistance can be improved by using NaCl (salt).

Ans: True.

2. An earth and ground wire is made of iron. 

Ans: False.

3. Earthing increases the resistance of the conductive path. 

Ans: False.

4. Earthing is used to provide supply voltage to an equipment. 

Ans: False.

5. The average resistance of the human body is 1500 Ohm. 

Ans: False.

6. In GI pipe earthing, 5 kg charcoal and 5 kg salt are required. 

Ans: False.

7. In transmission lines, plate earthing is used. 

Ans: False.

8. Strip earthing is also known as fire earthing. 

Ans: False.

9. For large power stations, the earthing resistance value is 0.5 Ohm. 

Ans: True.

10. The connection between electrical installation systems via conductor to the buried plate in the earth is known as earthing.

Ans: True.

D. Short answer questions:

1. What is earthing? 

Ans:Earthing, or grounding, refers to the process of transferring the immediate discharge of electrical energy directly to the earth using a low-resistance wire. This is done by connecting the non-current carrying parts of electrical equipment or the neutral point of a power supply system to the ground. The primary purpose is to avoid or minimize risks during the discharge of electrical energy, providing a safe path for fault currents to flow into the earth and prevent damage to the system or equipment.

2. Why is earthing required?

Ans: Earthing is required for the following reasons:

(i) Protection from Electric Shocks: It provides a safe path for the fault current to flow into the earth, protecting people from electric shocks.

(ii) Safety of Electrical Systems: It ensures the safety of electrical systems by preventing dangerous voltages from accumulating in case of equipment failure.

(iii) Safe Operation of Electrical Systems: Earthing ensures the stable and safe operation of electrical systems by providing a return path for faulty currents, preventing the risk of electrical hazards.

3. Write down some applications of earthing.

Ans: Some applications of earthing include:

(i) Protection from Electric Shocks: Earthing is used to protect individuals from electric shocks by providing a safe route for fault currents to flow into the ground.

(ii) Safety in Electrical Appliances: All electrical appliances, such as refrigerators, air conditioners, and washing machines, are earthed to prevent users from coming into contact with any stray currents that could cause harm.

(iii) Reducing Electrical Noise: Earthing can help reduce electrical noise and interference in electronic systems.

(iv) Protecting Equipment: Earthing helps to protect equipment from damage caused by electrical surges or faults.