22. The failure of a thermal relay may occur due to
A. motor and relay in different ambient temperatures
B. relay previously damaged by short-circuit
C. mechanical binding
D. all of these

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23. According to Indian Electricity rules, extra high voltage implies voltage exceeding
A. 440 V
B. 66 kV
C. 33 kV
D. 110 kV

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24. Resistivity of earth increases sharply if the moisture falls below
A.60%
B.50%
C.40%
D.20%

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25. Earth electrodes can be in the form of
A. rods and pipes
B. strips
C. plates
D. all of these

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26. PVC conduits can be buried on
A. lime
B. plaster
C. concrete
D. any of these

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27. Mixture preferred for filling around the earth for electrode efective earthing is
A. bone-meat mixture
B. coal-salt mixture
C. saw-dust sand mixture
D. lime-sand mixture

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28. Earthing is used as the return conductor for
A. telephone lines
B. telegraph lines
C. traction work
D. all of these

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