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Electrical Technology (12026) Experiment No.11

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

EXPERIMENT NO. 11

1.0 Title :

To understand method of earthing by drawing a neat sketch of plate earthing.

2.0 Prior Concepts:

Concept of resistance, Laws of resistance, Concept of leakage current, Concept of electric shock.3.0 New Concepts:

Proposition 1 : Earthing

The meaning of the term earthing or grounding is to connect the metallic body of electrical

equipment to the general mass of earth by a wire of negligible resistance.

Concept Structure 1 :

Proposition 2 : Purpose of Earthing

The earthing of an electrical installation has two purposes:

To provide safety to persons and animals against the danger of electric shock and/or

electric fire.

To protect the electrical equipments from the failures and electric fire.

Concept Structure 2 :

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Electrical Technology (12026) Experiment No.11

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

Proposition 3 : Earth Path

The path of electric current from the point of earth connection on the metallic body of electrical

equipment and earth is called as earth path.

Concept Structure 3 :

Proposition 4 : Resistance of Earthing

The Ohmic value of resistance of earth path is called as resistance of earthing. The resistance of

earthing depends upon following factors -

The resistivity of the soil surrounding the earthing plate,

The contact resistance between the earthing plate and the surrounding soil,

The resistance of the earthing plate and connecting conductors.

Concept Structure 4 :

4.0 Learning Objectives:4.1 Intellectual Skills:

To understand the method of earthing.

To understand the earthing and necessity of earthing.

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Electrical Technology (12026) Experiment No.11

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

4.2 Motor Skills:

Ability to draw a neat sketch of the plate earthing..

5.0 Sketch of Plate Earthing:

6.0 Redraw Sketch of Plate Earthing: (Student to draw)

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Electrical Technology (12026) Experiment No.11

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

7.0 Questions:Write answers to Q,Q,Q,Q, (The question numbers to be allotted by the teacher)

1. Define the term earthing.

2. State any two purposes of the earthing

3. What is mean by the term earth path ?

4. Define the term earth resistance.5. Why copper plate is used for the plate earthing?

6. Why earthing conductor is having larger cross-sectional area ?

7. Why copper is used for the earthing conductor?

8. Why charcoal and common salt is filled in the earthing pit surrounding the earthing plate ?

9. Why water is to be poured in the earthing pit ?

10. State the indications of good earthing.

Space for Answers