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Earthing

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Rural Technology

Defination -

The earthing of metal parts is achieved by connecting them to an earth conductor which shall be connected by means of an earthing lead to the earth electrode.

Necessity of Earthing -

The necessity for earthing is to ensure that the metalwork of electrical equipment, other than current carrying parts, cannot have a potential above earth in the event of a fault which might otherwise cause danger of an electric shock. If a fault is developed, causing unearthed metalwork of a piece of electrical equipment; it is charged to a level of dagerous potential. Any person touching the metal & at the same time comes in contact with earth will receive a severe electric shock. Had the metal been effectively earthed, the very low resistance of the circuit would result in a flow of current sufficient to blow the Fuse or to operate the protective device. In an earth metalwork of a piece of electrical equipment becomes a zero potential due to this; a person does not get a shock.

Plate type earthing -

This method requires the following materials-
1. Copper or G.I. earth plate.
2. Copper or G.I. earth wire.
3. Copper or G.I. nut, bolt & washer.
4. Funnel
5. G.I. Pipe.
6. Cast iron cover.
7. Salt, Charcoal & water.
A pit is dug in the ground. A copper plate or G.I. plate is buried vertically in the pit . An earth wire is bolted to the earth wire the help of nut, bolt & washer. The earth wire & the nut, bolts & washer should be of the same metal that of the plate used. A thick layer of salt & charcoal is placed around the earth plate, so as to reduce the earth resistnce & to maintain dampness. A G.I. Pipe is fitted over the plate. A funnel with a wiremesh cover is placed at the top of the pipe, & the whole arrangement is covered with a cast iron cover. In order to maintain the moistness around the earth plate, 3 or 4 buckets of water are poured in the pipe through the funnel.

2] INTEXT QUESTIONS-

a) Fill in the blanks-
1. Earthing is a _______ device.
2. Earthing ensures that a person cannot get a _______.
3. Eathing prevents the risk of _______ to human beings.

TERMINAL QUESTIONS-

1. Answers the questions-
a. What is the necessity of a Fuse?
b. What is the Fuse rating?
c. What is the Fusing current?
d. What precautions are to be taken while repairing a Fuse.
e. How do we make a plate earthing?
f. What is the function of an earthing?

1] Answers of Intext Questions-

a) Fill in the blanks-
1. safety
2. excess current
3. Kitkat & Piano type Fuse
4. Fuse
5. Series with line


b) True or False- 1. False 2. True 3. True 4. False 5. True 2] Answers of the Intext Questions- a) Fill in the blanks.
1. safety
2. shock
3. shock

Practical - 1

AIM -


Replacing of Fuse wire

Required Tools -


Wire cutter.
Electrician is screwdriver.

Required Material -


Tinned copper Fuse wire. ( 22 SWG or any )

Procedure -


1. Remove the blown Fuse wire.
2. Check the wire gauge.
3. Select proper size of the Fuse wire.
4. Connect the Fuse wire to Fuse carrier terminals properly.

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