Electrical Measurements Questions and Answers – Measurement of Earth Resistance

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
View Answer

Answer: a
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.
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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
View Answer

Answer: b
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
View Answer

Answer: c
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
View Answer

Answer: d
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
View Answer

Answer: a
Explanation: Earthing can be used to maintain a constant line voltage in a three phase system. This is achieved by earthing the neutral.
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6. Earthing is used as return conductor in telephone lines and for traction work.
a) True
b) False
View Answer

Answer: a
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
View Answer

Answer: b
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
View Answer

Answer: c
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

Answer: d
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.
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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

Answer: a
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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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Instagram | Facebook | Twitter