Ecet 110

ECET 110
Week 3 Homework
10/23/2012

Chapter 7
1) Which elements of the networks in Fig. 7.60 are in series? Which are in parallel? As a check on your assumptions, be sure that the elements in series have the same current and that the elements in parallel have the same voltage. Restrict your decisions to single elements, not combinations of elements.
(a)R1, R2, and E are in series; R3, R4, and R5 are parallel.
(b)E and R1 are in series; R2, R3, and R4 are parallel.
(c)E and R1 are in series; R2, R3, and R4 are parallel.
2) Determine Rt for the networks in Fig. 7.61.
(a)R’= R2R4/R2+R4= 10Ohms*4Ohms/10Ohms+4Ohms= 3Ohms
R’’=R1R5/R1+R5= 4Ohms*4Ohms/4Ohms+4Ohms= 2Ohms
Rt= R’+R3+R’’= 3Ohms+4Ohms+2Ohms= 9Ohms
(b)Rt= R1+R2+R3= 10Ohms+10Ohms+10Ohms= 30Ohms
3) Find the total resistance for the configuration of Fig. 7.62.
R’= R1R2/R1+R2= 2.2kOhms*10kOhms/2.2Ohms+10kOhms= 20kOhms
R’’=R3R4/R3+R4= 2.2kOhms*10kOhms/2.2Ohms+10kOhms= 20kOhms
Rt= R’+R’’= 20kOhms+20kOhms= 40kOhms
8) For the network of Fig. 7.67:
(a) Find the voltages Va and Vb.
Va= 32V
Vb= R2/I1= 12Ohms*3A= 36V
(b) Find the currents I1 and Is.
I1= 32V/12Ohms= 3A
Is= V/Rt= 32V/74Ohms= 0.4mA
10) For the circuit board in Fig. 7.69:
(a)Find the total resistance Rt of the configuration.
R’= R6R5/R6+R5=3.3kOhms*2.4kOhms/3.3kOhms+2.4kOhms=1.4kOhms
R’’= R’*RR4/R’+R4=1.4kOhms*2kOhms/1.4kOhms+2kOhms=1kOhm
Rt= R1+R2+R3+R’’=1kOhm+1.2kOhms+6.8kOhms+1kOhm=10kOhms
(b) Find the current drawn from the supply if the applied voltage is 48 V.
Is= V/Rt= 48V/10kOhms= 4.8mA
(c) Find the reading of applied voltmeter.