This set of Electrical Measurements Questions and Answers for Aptitude test focuses on “Measurement of Earth Resistance”.
1. What is earthing?
a) connecting electrical machines to earth
b) providing a connection to the ground
c) connecting the electrical machines to source
d) providing a source of current
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Explanation: Connecting electrical machines to the general mass of the earth by making use of a conducting material with very low resistance is known as earthing.
2. What is an earth electrode?
a) electrode that is connected to earth
b) material used for earthing
c) electrode connected to the circuit
d) electrode which is connected to the mains
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Explanation: Electrode connected to the main is basically a source of e.m.f. Conducting material that is used for connecting electrical machinery to the earth is known as an earth electrode.
3. Earth electrode provides ____________
a) high resistance
b) medium resistance
c) low resistance
d) very high resistance
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Explanation: In the case of occurrence of any leakage currents due to poor shielding of the apparatus, the earth electrode is used to provide a very low resistance path from the electrical appliances to the earth.
4. How is the condition of an earth electrode measured?
a) by measuring the voltage
b) by measuring the current
c) by measuring the power
d) by measuring resistance
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Explanation: The resistance of the earth electrode is measured in order to check whether it is in a good condition or not.
5. In a three phase system, the neutral is _________
a) earthed
b) connected to low voltage
c) connected to high voltage
d) not connected
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Explanation: Earthing can be used to maintain a constant line voltage in a three phase system. This is achieved by earthing the neutral.
6. Earthing is used as return conductor in telephone lines and for traction work.
a) True
b) False
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Explanation: The complications involved in laying separate telephone cables and the cast used for traction work is minimised. As a result earthing is used as a return conductor in telephone lines and for traction work.
7. Earthing does not help in protecting the equipment.
a) True
b) False
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Explanation: Spike voltages occurring as a result of lightning or any other fault can be dissipated to ground by earthing, thus protecting the equipment.
8. After earthing, the different parts of an electrical machinery are at _________
a) infinite potential
b) intermediate potential
c) zero potential
d) undefined potential
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Explanation: After earthing, the various parts of electrical machinery such as casing, armoring of cables, etc are at zero potential.
9. Connection of the various parts of a circuit to earth has a _________
a) medium resistance
b) high resistance
c) very high resistance
d) very low resistance
View Answer
Explanation: Once an electrical apparatus is grounded, most of its components are at ground potential. When the different parts of electrical machinery are connected to the ground, they possess very low resistance.
10. Specific resistance of soil is _________
a) changes from soil to soil
b) is constant
c) depends on the circuit connected to it
d) depends on the supply voltage
View Answer
Explanation: Specific resistance depends on the nature and properties of a material. Specific resistance is different for various types of soils such as dry soil, rocky soil, wet soil, etc.
Sanfoundry Global Education & Learning Series – Electrical Measurements.
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