SEATWORK:
1. A transformer is designed to carry 30 time its rated current for 1 second. The
length of time that a current of 20 times the rated current can be allowed to flow
is
a. 0.67 sec
b. 2 sec
c. 1.5 sec
d. 2.25 sec
2. A water turbine operating at 85% efficiency is under a head of 100m. If the
constant discharge is 1000 gal/sec, evaluate the operating speed of the turbine.
a. 640 rpm
b. 654 rpm
c. 636 rpm
d. 608 rpm
3. Four lamps are suspended 6m above the ground at the corners of a lawn 4m on
each side. If each lamp emits 250 cd, calculate the illumination at the center of
the lawn.
a. 20.56 lux
b. 22.34 lux
c. 21.62 lux
d. 19.85 lux
4. A 3 phase, 375kVA, 480V, 50Hz, wye connected alternator has an equal positive
and negative sequence reactance of 10%. Find the symmetrical fault current, if a
3 phase fault occurs at the alternator terminals.
a. 4510.5 A
b. 4620.3 A
c. 4255.2 A
d. 4778.1 A
5. A balanced 3 phase load draws 150 A phase current at 7.5kV phase to neutral,
0.891 power factor lagging. It is desired to raise the power factor to 0.96 leading.
Solve for the amount of capacitor kVAR needed to achieve such pf.
a. 2273 kVAR
b. 2409 kVAR
c. 2509 kVAR
d. 2365 kVAR
6. A capacitive load always has a ________ power factor.
a. Leading
b. Lagging
c. Factor
d. Unity
7. The temperature coefficient of resistance of insulator is
a. Zero
b. Negative
c. Positive
d. Infinite
8. Which of the following materials serves as protection against overload?
a. Fuse
b. Switch
c. Resistor
d. Relay
9. An ideal current source has an internal conductance of ______ siemen/s.
a. Infinite
b. One
c. Zero
d. One million
10. A circuit whose parameters change with voltage or current
a. Non-linear circuit
b. Linear circuit
c. Complex circuit
d. Passive circuit