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Unformatted text preview: re in parallel if they are connected to
the same two nodes. Elements in parallel always have the same
voltage across them (v1 = v2 ).
8. When two resistors R1 (= 1/G1 ) and R2 (= 1/G2 ) are in series,
their equivalent resistance Req and equivalent conductance Geq are
Req = R1 + R2 , Geq = G 1 G2
G1 + G 2 9. When two resistors R1 (= 1/G1 ) and R2 (= 1/G2 ) are in parallel,
their equivalent resistance Req and equivalent conductance Geq are
Req = R 1 R2
,
R1 + R 2 Geq = G1 + G2 10. The voltage division principle for two resistors in series is
v1 = R1
v,
R1 + R 2 R2
v
R1 + R 2 v2 = 11. The current division principle for two resistors in parallel is
i1 = R2
i,
R1 + R 2 i2 = R1
i
R1 + R 2 12. The formulas for a deltatowye transformation are
R1 = Rb Rc
,
Ra + R b + R c
R3 = R2 = R c Ra
Ra + R b + R c R a Rb
Ra + R b + R c 13. The formulas for a wyetodelta transformation are
Ra = R1 R2 + R2 R3 + R3 R1
,
R1
Rc = Rb = R1 R2 + R2 R3 + R3 R1
R2 R1 R2 + R2 R3 + R3 R1
R3 14. The basic laws covered in this chapter can be applied to the problems of electrical lighting and design of dc meters. REVIEW QUESTIONS  The reciprocal of resistance is:
(a) voltage
(b) current
(c) conductance
(d) coulombs v v 2.1  eText Main Menu 2.2  Textbook Table of Contents  An electric heater draws 10 A from a 120V line.
The resistance of the heater is:
(a) 1200
(b) 120
(c) 12
(d) 1.2 Problem Solving Workbook Contents 61 62 PART 1 DC Circuits 2.3 The voltage drop across a 1.5kW toaster that draws
12 A of current is:
(a) 18 kV
(b) 125 V
(c) 120 V
(d) 10.42 V 2.4 The maximum current that a 2W, 80 k
safely conduct is:
(a) 160 kA
(b) 40 kA
(c) 5 mA
(d) 25 µA 2.9 Which of the circuits in Fig. 2.66 will give you
Vab = 7 V? resistor can 5V
+− 2.5 3V +
− A network has 12 branches and 8 independent loops.
How many nodes are there in the network?
(a) 19
(b) 17
(c) 5
(d) 4 2.6 5V The current I in the circuit in Fig. 2.63 is:
(a) −0.8 A
(b) −0.2 A
(c) 0.2 A
(d) 0.8 A −+ b 1V 1V (a) (b)
5V 5V 3V +
− +− +
− b 3V +
−
+− I...
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 Spring '12
 bkav

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