assignment engr2200 fall11 w

Instructor: Walid Morsi Ibrahim

Faculty of Engineering and Applied Sciences

ENGR 2200 Electric Engineering Fundamentals

Assignments Assignments are due on Thursday (Class time) Fall 2011

All problems for Assignments (1-3) are from the textbook: “Electric Circuits”, 9th

edition by J.W. Nilsson and S. A. Riedel, Prentice Hall, 2011.

Assignment 1:

Problem 2.4 Problem 2.19 Problem 2.26 Problem 3.11

Assignment 2:

Problem 4.17 Problem 4.39 Problem 4.71 Problem 4.79

Problem 4.92

Assignment 3:

Problem 6.1 Problem 6.15

Assignment 4:

Problem 1

Determine the rms value for each of the waveforms shown:

(a) (b) (c)

Problem 2

For the voltage waveform shown in Fig. 2:

a- Find the rms value.

b- If this voltage is applied to the terminals of a 12 resistor, what is the average power dissipated in the resistor.

Ati )(


Fig. 2

Problem 3

For the circuit shown in Fig. 3:

a- Use nodal analysis to find the voltage 1V assuming is 100 rad / sec.

b- Find the amount of active power in watts delivered to each element and state whether it is generated (G) or absorbed (A).

c- Find the amount of reactive power in VARs delivered to each element and state whether it is generated (G) or absorbed (A).

Fig. 3

Problem 4

For the following phasor diagrams shown in Fig. 4, calculate the power factor and state whether it is leading or lagging.

(a) (b) (c) (d)

Fig. 4

040 10

15F500

1V

12

3V

90

V

I45 V

I90V

I

I

V

90


Problem 5

The three loads in the circuits shown in Fig. 5 are 251 jS kVA, 5.175.32 jS kVA, and

083 jS kVA.

a- Calculate the complex power associated with each voltage source.

b- Verify that the total real and reactive power delivered by the sources equals the total real and reactive power absorbed by the network.

Fig. 5

Problem 6

A group of small appliances on a 60 Hz system requires 25 kVA at 0.96 pf lagging when operated at 125 V (rms). The impedance of the feeder supplying the appliances is 0.006 + j 0.048 Ω. The voltage at the load end of the feeder is 125 V.

a- What is the rms magnitude of the voltage at the source end of the feeder?

b- What is the average power loss in the feeder?

c- What size capacitor at the load end of the feeder is needed to improve the load power factor to unity?

d- After the capacitor is installed, what is the rms magnitude of the voltage at the source end of the feeder if the load voltage is maintained at 125 V?

e- What is the average power loss in the feeder for (d)?

Problem 7

Determine the values of R and L for the load of the circuit shown in Fig. 6 that cause maximum power transfer to the load. Also determine the amount of that maximum power.

Fig. 6

2gV

1gV

05.0

14.0

05.0

1S

0125

2S

3S

0125

F5.0

k4

R

Lsec/10

605

3 rad

Source Load


aV

bVcV

5080 j

3020 j 4060 j

aI

bI

cI

Assignment 5:

Problem 1

Determine the line currents for the three-phase

circuit of Figure 1.

Let ,120110,0110 VVVV ba

and VVc 120110.

Fig. 1

Problem 2

A 25-hp (1 hp = 746 Watts) induction motor is operating at rated load from a three-phase, 450 V, 60 Hz system. The efficiency and power factor of the motor are 87 percent and 90 percent lagging respectively. Determine (a) the active power in kW, (b) the apparent power in kVA, (c) the reactive power in kVAR and (d) the line current in amperes.

assignment engr2200 fall11 w

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