Basic Electrical Engineering MCQ_59_1 (Earthing)

Q.1 soil resistivity is expressed in___.
    A. Ohm-meter
    B. Ohm/ meter
    C. Ohm
    D. meter/ohm
Ans.: A

Q.2 The two main factors which influence the soil resistivity value are the ___and ____.
    A. porosity of the material
    B. the water content
    C. type of electrodes
    D. Both A and B
Ans.: D

Q.3 The ____ and _____ have an important influence on the soil resistivity and hence on the performance of earthing system.
    A. Temperature
    B. Water content
    C. Both A and B
    D. none of the above
Ans.: C

Q.4 Why it is necessary to install the electrodes beneath the freezing line?
    A. Ice has very high resistivity as compared to water
    B. Ice has very low resistivity as compared to water
    C. Ice and water are same resistivity
    D. Any of the above
Ans.: A

Q.5 The water content varies with seasonally and likely to cause variation in the_____.
    A. Temperature of earth
    B. Electrode conductivity
    C. resistance of earthing system
    D. all of the above
Ans.: C

Q.6 Which of the following is/are correct formula for calculation of soil resistivity?
    A. ρ = л AR
    B. ρ = 2AR
    C. ρ = 2лR
    D. ρ = 2лAR
[ρ = average soil resistivity in ohm-cm, A= distance between the electrode, R= the measured resistance value in ohm]
Ans.: D

Q.7 _____ in the water further reduced the resistivity of earthing particular where there are naturally occurring and do not dilute with time.
    A. Dissolve minerals
    B. salt
    C. Both A and B
    D. None of the above
Ans.: C

Q.8 If the working voltage of the transmission line is very high, the magnitude of earth fault current is also___.
    A. very low
    B. very high
    C. depend on soil
    D. all of the above
Ans.: B

Q.9 The size of the conductor must be chosen in such a way that it can withstand the_____ produced by earth fault current until the protective relay comes into action and isolates the faulty portion of the system.
    A. high resistance
    B. high earth fault current
    C. high temperature
    D. high voltage
Ans.: C

Q.10 Which of the following is correct for the minimum cross sectional area of the earth conductor?
    A. A = Ifault/C mm2
    B. A = Ifault√t  mm2
    C. A = √t /C mm2
    D. A = Ifault√t /C mm2
Ans.: D
[A = minimum area of conductor required, t = time in second which is required for the operation of the C.B, C = constant whose value depends upon the nature of material]

Q.11 The melting point of aluminium is ____ than copper.
    A. higher
    B. less
    C. equal
    D. none of the above
Ans.: B

Q.12 The ___ is defined as the potential difference between two steps of a person standing on the ground with feet apart during the flow of earth fault current.
    A. Earth resistivity
    B. Earth resistance
    C. Electrode resistance
    D. Step potential
Ans.: D

Q.13 ___ consists of large number of rods which are connected through the copper conductor.
    A. Earthing mat
    B. Earthing wire/ conductor
    C. Earthing electrode
    D. All of the above
Ans.: A

Q.14 The material used for the grounding conductor should have ____ and ___.
    A. low conductivity, low underground corrosion
    B. high conductivity, high underground corrosion
    C. high conductivity, low underground corrosion
    D. low conductivity, high underground corrosion
Ans.: C

Q.15 The modern trend is towards the use of ___in place of copper for the material use for grounding.
    A. steel
    B. Aluminium
    C. tungsten
    D. all of the above
Ans.: A

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