EE301
Name
Date
HW26
Section
Instructor
1) Power factor is the ratio of the average power to the apparent power. True or False?
1)
2) The unit of apparent power is the volt-ampere. True or False?
2)
3) In a certain electric circuit, if PT = 600 W, ST = 1000 VA, and Q T = 800 VAR (capacitive), what is
the power factor?
A) 0.75 leading
B) 0.6 leading
C) 0.8 leading
D) 0.5 leading
4) See Figure 1. The power triangle shown represents the characteristics of a 230 V 60 Hz ac motor.
What is the power factor of this motor?
A) 0.866
B) 0.5
C) 0.577
D) 1.0
Figure 1
5) See Figure 1. How much current is consumed by this motor if the supply voltage is 230 V ac at 60
Hz?
A) 7.53 A
B) 0.23 A
C) 4.35 A
D) 8.70 A
1
6) See Figure 2. Sketch the power triangle for this network. Calculate the supply current I.
Figure 2
7) A 10 hp motor has an efficiency of 75% and a power factor of 0.8 (lagging). How much input power is consumed?
A) 7460 W
B) 9943 W
C) 9325 W
D) 5595 W
8) A 10 hp motor has an efficiency of 75% and a power factor of 0.8 (lagging). How much apparent power is consumed?
A) 7460 VA
B) 13,262 VA
C) 5595 VA
D) 12,428 VA
C) 94.1%
D) 78.7%
9) What is the power factor for the circuit in Figure 3?
A) 98.7%
B) 83.7%
Figure 3
E= 10∠5
2