Basic Electrical Engineering MCQ

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Basic Electrical Engineering MCQ_60

Earthing

Q.1 Which of the following information is necessary to obtain for design of substation earthing grid for substation?

1 point

maximum earth fault current, fault clearing time

Area covered by the substation

Resistivity of the soil at the sub-station site

all of the above

Clear selection

Q.2 The degree of protection provided by a grounding system under lightning discharge conditions depends upon its _____ rather than on power frequency impedance.

1 point

Resistance

impulse impedance

reactance

all of the above

Clear selection

Q.3 What is impulse impedance?

1 point

The impedance under normal conditions

The impedance under impulse conditions

The impulse under transient conditions

all of the above

Clear selection

Q.4 The impulse impedance is always ____ than its power frequency impedance.

1 point

lower

higher

equal

any of the above

Clear selection

Q.5 Resistivity of water depends on the ___ and ____ of salt dissolved in it.

1 point

amount, nature

temperature, anture

purity, nature

none of the above

Clear selection

Q.6 Pure water is poor conductor of_____.

1 point

temperature

sound

electricity

all of the above

Clear selection

Q.7 Which of the following is/are correct for effect of current flowing through human body?

1 point

Below 1 mA = nothing

11 to 25 mA = painful shock with muscle contraction after medical treatment they can restored

Above 150 mA = cardiac arrest, body starts burning resulting into death

all of the above

Clear selection

Q.8 Current flows from earthing grid during ____ creating potential difference.

1 point

operation and working

faults

lighting

all of the above

Clear selection

Q. 9 Impulse performance of earthing system depends on which of the following factors?

1 point

electrical soil proporties

ground electrode geometry

current waveform proporties

all of the above

Clear selection

Q.10 Tower footing resistance should be below ___.

1 point

10 Ω

50 Ω

40 Ω

20 Ω

Clear selection

Q.11 Material used for tower footing can be____.

1 point

iron clad

copper plates

Both A and B

tungsten

Clear selection

Q.12 ____ is very good in improving or increasing the conductivity of soil as compared to others.

1 point

Sea water

pure water

common salt

Drinking water

Clear selection

Q.13 A human body can tolerate a current slightly higher than ___.

1 point

10 Hz

5 Hz

15 Hz

25 Hz

Clear selection

Q.14 If the depth of earth electrode is increases, the value of ground resistance can be____.

1 point

increases

minimized

does not depend on the depth of electrode

none of the above

Clear selection

Q.15 Which of the following common paths for current to flow through the body?

1 point

Hand to foot

Hand to hand through the chest

foot to foot

all of the above

Clear selection

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