EE REFRESHER 1

1. Find the current in a conductor through which

2.5x10
20
free electrons pass in 8 seconds.
A. 3 A C. 2 A
B. 5 A D. 7 A

2. Calculate the resistance of a hard drawn copper
wire having a radius of 0.125 in and a length equal to
10 ft.
A. 1.6592 m C. 1.704 m
B. 2.6342 m D. 2.220 m

3. A 6 resistor is connected in series to a parallel
connection of a 30 resistor and a variable resistor
R. What must be the value of R such that the power
taken by the 6 resistor will be equal to the power
taken by R?
A. 14.98 C. 12.58
B. 9.45 D. 11.46

4. A resistor and an inductor are connected in parallel to
a 120 V, 60 Hz source. If the total current and power
in the circuit are respectively 17 A and 1800 W, find
the value of L.
A. 0.0398 H C. 0.0455 H
B. 0.0284 H D. 0.0338 H

5. A voltage wave is given by e = 100 sin 314t. How
long does it take this waveform to complete one-
fourth cycle?
A. 2 ms C. 8 ms
B. 5 ms D. 4 ms

6. A current of 5 A flows through a resistance in series
with a choking coil when applied at 250 V, 60 Hz. If
the voltage across the resistance is 125 volts and
across the coil is 200 volts, determine the inductance
of the coil.
A. 0.124 H C. 0.222 H
B. 0.102 H D. 0.454 H

7. The equation of an alternating emf is e = 155sin(157t
+ 30) V. What is value of t in seconds when e first
reaches a maximum negative value?
A. 0.027 sec C. 0.086 sec
B. 0.052 sec D. 0.061 sec

8. A unity power factor load of 1794 watts is connected
in parallel with a load of 1656 watts operating at a
lagging pf of 0.6. If the line voltage is 115 V, calculate
the total current.
A. 28.55 A C. 32.23 A
B. 41.72 A D. 35.62 A

9. An impedance load consisting of 12 ohms resistance
and 16 ohms inductive reactance is connected across
a 60 Hz, 100 V source. Find the capacitance of the
condenser which may be paralleled with this load to
bring the power factor to 0.8 lagging.
A. 61.33 F C. 53.45 F
B. 38.79 F D. 46.42 F

10. A single phase motor is rated 5 hp, 75% pf and 220
volts. What is the approximate size of the capacitor
necessary to raise the power factor to about 95%?
A. 1.055 kVAR C. 2.063 kVAR
B. 2.521 kVAR D. 3.445 kVAR

11. If V
an
= 20040 volts, determine V
AC
.
A. 2003160 V C. 2003-200 V
B. 2003-170 V D. 200310 V

12. A balanced three phase connected load draws 20
kW at a power factor of 0.4. The frequency is 60 Hz.
If the line voltage at the load terminals is 1,300 V,
calculate the value of each capacitance for delta
connection.
A. 28.544 microfarad C. 30.776 microfarad
B. 25.863 microfarad D. 22.523 microfarad

13. A balanced delta connected load, with impedance
10 -36.9 , and a balanced Y connected load
are supplied by the same three phase ABC system
having Vca = 141.4240 V. If the current in line A is
40.44133.41 A, what are the impedances of the Y
connected load?
A. 5cis-60 C. 4cis-30
B. 5cis-53.3 D. 4cis-66.7

14. A factory is supplied by a three phase, three wire
system with the following characteristics.
V
AB
= 230cis0 V I
A
= 110cis-36.87 A
V
BC
= 230cis240 V I
C
= 125cis53.13 A
Determine the average power factor of the load.
A. 0.878 lagging C. 0.851 lagging
B. 0.922 lagging D. 0.934 lagging

15. Determine the operating power factor of a three
phase balanced load if the readings of the two
wattmeters properly connected to measure power is
3:1
A. 0.866 C. 0.778
B. 0.756 D. 0.922

16. Given a balanced 3-wire, three phase system
serving the following loads:
V
ab
= 200cis0 V Z
ab
= 10cis53.13
V
bc
= 200cis240 V Z
bc
= 10
V
ca
= 200cis120 V Z
ca
= 10cis30
Determine the current on line b.
A. 20.34 A C. 24.36 A
B. 22.04 A D. 21.57 A

17. A load is supplied by a three phase, 3 wire system
with the following characteristics:
Vab = 230cis0 V Ia = 110cis-36.87 A
Vbc = 230cis240 V Ic = 125cis53.13 A
Determine the power consumed by the load.
A. 45.12 kW C. 48.78 kW
B. 41.55 kW D. 47.98 kW

18. A 240 V three phase system supplies a 100 kW,
0.6 lagging balanced load. Determine the
capacitance in each phase of a wye connected
capacitor bank in order to adjust the power factor to
0.95 lagging.
A. 4.63 F C. 5.3 F
B. 11.10 mF D. 100.47 mF

19. In a balanced star-connected system, the line
voltages are __ ahead of their respective phase
voltages.
A. 30 C. 120
B. 60 D. 45

20. A three phase motor takes 10 kVA at 0.6 power
factor lagging from a source of 220 V. It is in parallel
with a balanced delta connected load having 16 ohm
resistance and j12 reactance in series with each
phase. Find the total kVAR of the combination.
A. 8.43 C. 3.64
B. 12.35 D. 15.33




21. A 3-phase 50-HP, 440 V 60-Hz induction motor
operates on full load with an efficiency of 80% and a
power factor of 0.85 lagging. It is required to raise
the full load power factor 0.95 lagging by using
capacitor bank connected in delta. What will be the
capacitance per phase in microfarads?
A. 61.98 F C. 53.48 F
B. 52.58 F D. 63.63 F

22. Consider two point charges of +q and +4q which are
separated by a distance of 3 meters. At what point
(from +q) on the line joining the two charges, is the
electric field equal to zero?
A. 1 m C. 3 m
B. 2 m D. 2.5 m

23. Charge one of +4 C is located at (2, 0, 0). Charge
two of -5 C is located at (0, 0, 2). What is the force
between them?
A. 0.0823 N C. 0.0225 N
B. 0.067 N D. 0.055 N

24. The energy stored in a 3.6 F capacitor with an
applied voltage of 15 volts is
A. 0.634 mJ C. 0.405 mJ
B. 0.3 mJ D. 0.556 mJ

25. The wing span of a metal airplane is 36 m. If the
plane is flying at 400 kph, determine the emf
induced between the wingtips. Assume that the
vertical component of the earths magnetic field is 40
T.
A. 0.20 V C. 0.18 V
B. 0.57 V D. 0.16 V

26. A conductor of 150 cm moves at an angle of 30 to a
uniform magnetic field of strength 0.8 Tesla with a
velocity of 30 m/s. Determine the induced emf.
A. 20 V C. 36 V
B. 18 V D. 30 V

27. A short shunt compound generator has a full load
current of 60 A. If the series field resistance is 0.04
and the diverter carries 24 A, calculate the diverter
resistance.
A. 0.06 C. 0.01
B. 0.04 D. 0.02

28. A 4-pole wave wound dc generator has 50 slots and
24 conductors per slot. The flux per pole is 10 mWb.
Determine the induced emf in the armature, if it is
rotating at a speed of 600 rpm.
A. 240 V C. 120 V
B. 200 V D. 180 V

29. A 10 kW long shunt compound generator has a load
voltage of 230 V. The shunt field has 800 turns per
pole and the series field has 8 turns per pole. The
shunt field and series field resistances are 80 and
0.07 , respectively. To make the generator flat
compounded, the series field must produce 225
ampere turns. Calculate the diverter resistance to
accomplish this change.
A. 0.033 C. 0.069
B. 0.093 D. 0.054

30. A 150 hp, 600 V, 205 A, shunt motor is running at
1700 rpm full load. The resistance of the shunt field
circuit is 240 and the total armature circuit
resistance is 0.15 . Calculate the speed regulation
of the motor.
A. 5.08% C. 5.28%
B. 5.18% D. 5.38%


31. A 90-slot stator has a 3-phase, six pole winding.
Each coil spans from slot 1 to slot 14. Calculate the
armature winding distribution factor.
A. 0.978 C. 0.936
B. 0.957 D. 0.927

32. From the previous problem, calculate the winding
factor.
A. 0.867 C. 0.936
B. 0.957 D. 0.978

33. A 3 phase wye connected 1000 kVA, 2300 V
alternator is short circuited & operated at rated
speed to produce rated current. With the short circuit
removed and the same excitation, the voltage
between terminals is 1300 V. The effective armature
resistance between terminals is 2 ohms. Determine
the per cent regulation at a power factor of 0.8
lagging.
A. 54.4 % C. 50.37 %
B. 57.34 % D. 56.69 %

34. Calculate the pitch factor for an alternator winding
with 72 slots, 6-poles, and coil span of 1 to 10.
A. 0.8934 C. 0.9239
B. 0.9428 D. 0.9750

35. Two alternators operating in parallel supply the
following loads: A =400 kW, unity pf; B=1000 kW,
0.707 lagging pf; C= 600 kW, 0.90 leading pf. One
machine supplies 800 kW at 0.866 lagging power
factor. What is the power factor of the other
machine?
A. 0.983 lagging C. 0.979 lagging
B. 0.971 lagging D. 0.908 lagging

36. A wye connected, 1000 kVA, 11 kV synchronous
motor has a synchronous impedance of (3.5 + j40)
ohms. When fully loaded at 0.80 lagging power
factor, the induced emf between lines is nearest to
A. 5899 V C. 9872 V
B. 8985 V D. 1029 V

37. A single phase transformer has a net core area of 60
cm
2
. The primary having 400 turns is connected to a
550 volt supply. What is the flux density in the
core? The supply frequency is 60 Hz.
A. 0.78 T C. 0.94 T
B. 0.86 T D. 1.08 T

38. A 400 MVA, 240 kV/24 kV, three phase wye delta
transformer has an equivalent series impedance of
1.2 + j6 ohms per phase referred to the high voltage
side. The transformer is supplying a three phase
load of 400 MVA, 0.8 pf lagging at a terminal voltage
of 24 kV (line to line) on its low voltage side. The
primary is supplied from a feeder with an impedance
of 0.6 + j1.2 ohms per phase. Determine the line to
line voltage at the sending end of the feeder.
A. 247.09 kV C. 244.687 kV
B. 249.09 kV D. 243.221 kV

39. When a is the operator, a a2 is equal to _____.
A. 0 C. 1
B. -1 D. j (sqrt of 3)

40. A load of 25 MW, 0.8 pf lagging is delivered by a
three phase supply having a resistance per phase
per km equal to 0.5576. If the load voltage is 132 kV
between lines and the losses in the transmission line
is 7.5% of the load, calculate the distance over
which the load can be delivered.
A. 50 km C. 60 km
B. 55 km D. 65 km

41. In a three phase transmission conductors are
arranged at the corners of an equilaline, the teral
triangle of each side 2.5 m. If the radius of each
conductor is 0.8 cm, determine the inductance per
phase per kilometre length of the line.
A. 1.2 mH/km C. 2.4 mH/km
B. 3.5 mH/km D. 5.5 mH/km

42. Medium transmission lines are up to ____ km.
A. 80 C. 240
B. 200 D. 300

43. A 50 MVA, 33 kV/11 kV, three phase, wye delta
connected transformer has a 3 % impedance. What
is the per cent impedance at 100 MVA base and
34.5 kV base?
A. 5.02 % C. 5.49 %
B. 6.92 % D. 6.24 %

44. Determine the three phase fault current in a power
system that has a positive, negative, and zero
sequence reactances of 0.5 pu, 0.5 pu, and 0.26 pu,
respectively. kV and MVA bases are 115 and 100.
A. 1004 A C. 8006 A
B. 4001 A D. 6008 A

45. A 4x4 Z bus matrix has the following per cent
impedances corresponding to each element: Z11 =
j0.11 pu, Z12 = j0.18 pu, Z13 = j0.12 pu, Z14 = j0.24
pu, Z21 = j0.21 pu, Z22 = j0.18 pu, Z23 = j0.16 pu,
Z24 = j0.24 pu, Z31 = j0.43 pu, Z32 = j0.14 pu, Z33
= j0.3 pu, Z34 = j0.56 pu, Z41 = j0.72 pu, Z42 =
j0.17 pu, Z43 = j0.13 pu, Z44 = j0.25 pu. Calculate
the three phase fault of the power system if the
fault occurs on bus 4 of the system. Base MVA and
Base kV are 200 and 13.8, respectively.
A. 33.5 kA C. 29.2 kA
B. 47.2 kA D. 51.8 kA

46. The positive, negative, and zero sequence
reactances of a 20 MVA, 13.2 kV synchronous
generator are 0.3 pu, 0.2 pu, and 0.1 pu.,
respectively. The generator is solidly grounded and
is not loaded. If a double line to ground fault occurs
at the generator terminals b and c, determine the
line voltage Vab.
A. 4.16 kV C. 6.72 kV
B. 7.62 kV D. 5.35 kV

SITUATION: A synchronous generator rated at 20
MVA, 13.8 kV has the following subtransient
reactances:
X1 = j0.25 pu
X2 = j0.35 pu
X0 = j0.10 pu
The machine has a bolted fault and the neutral
is solidly grounded.

47. Determine the three phase fault.
A. 3586 A C. 5956 A
B. 3347 A D. 2415 A

48. Calculate the single line to ground fault.
A. 3586 A C. 5956 A
B. 3347 A D. 2415 A

49. Calculate the line to line fault.
A. 3586 A C. 5956 A
B. 3347 A D. 2415 A

50. Determine the double line to ground fault.
A. 3586 A C. 5956 A
B. 3347 A D. 2415 A