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Electrical Engineering Objective Questions { Power System }

1. A 110-V, 2-wire de line is converted into a 3-wire, 110/220 V line by adding a wire similar to that used in the 2-wire line. If same line loss is maintained then
A. power transmission would be doubled
B. each wire will carry one-third of the load current when the load is equally balanced between the two sides of the line.
C. the only advantage is that 200-V motors can be operated
D. the amount of copper would have been increased by 33.3%

2. Which of the following generating station has the minimum running cost?
A. hydro-electric station
B. nuclear power station
C. thermal power station
D. diesel power paint

3. One favourable economics factor in the transmission of power at high voltages is the
A. decreased insulation required by the line
B. increased 12R losses
C. smaller size of the generating station
D. reduction of conductor cross-section

4. The letters D.P.D.T. identify a
A. conduct
B. switch
C. thick wire
D. fuse

5. Differential relays are installed to protect the equipment against
A. reverse current
B. internal faults
C. overcurrents
D. no voltage

6. The most important reason for not using the neutral in a 110/220-V, 3-wire system is that
A. increased cost of a 3-fuse outlet out-weighs its advantages
B. additional fuse protection is unnecessary
C. blowing of a neutral fuse may produce a serious voltage imbalance in the circuit
D. a neutral fuse increases the hazard of shccks

7. When switch S is closed in Figure, it is reasonable to expect the blowing of fuse
A. F1 but not F2 and F3
B. F2 and F3 but not F1
C. F1 and F2 but not F3
D. F1, F2 and F3

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