D. Linear element of the circuit is such one whose characteristic is a straight line.

E. Battery is considered as voltage source.

 

Solution:

D – wrong. Linear means that the defining characteristic is a straight line through the origin. Elements whose characteristics do not pass through the origin (even if it’s a straight line) or are not a straight line are said to be nonlinear.

Answer: D.

 

71. We know R_A, R_B, and R_C for delta. What is R₂ for delta-to-star transformation? (see Fig. 1).

A. R₂ = (R_A + R_B + R_C)/ R_A B. R₂ = R_BR_C/ (R_A + R_B + R_C)

C. R₂ = R_AR_C/ (R_A + R_B + R_C) D. R₂ = R_BR_A/ (R_A + R_B + R_C)

E. R₂ = R_BR_C/ (R_A + R_B)

 

 

Fig.1

 

Solution:

Answer: C.

 

72 What is the value of current I? (see Fig.2)

A. 2A B. – 1A C. 5A D. 1A E. – 2A

 

Solution:

Both current sources are directed in the same direction, so the resulting current source will be presented as the sum I=2+3=5A.

Answer: C.

 

 

Fig. 2

 

73. What is equivalent resistance for the circuit below if R₁=15 Ω, R₂=R₅=10 Ω, R₃=R₄=30 Ω?

A. 20 Ω B. 30 Ω C. 40 Ω D. 50 Ω; E. 60 Ω;

Solution:

Let’s simplify R₃ and R₄ parallel arrangement:

Note: When two resistors connected in parallel and

have the same value R, simplifying to one resistor

will give value R/2.

Now series arrangement of R₁, R₂, R_EQ and R₅ will give

Answer: D.

 

 

74. What is the value of V_X for the circuit in Fig.5? A. 10V B.5V C.-5V D.-10V E. –15V

Solution:

Let’s consider the node at the center of the circuit.

Current from left branch is I₁=8/2*10³= 4mA.

By KCL: 4+5–10–i_x=0. i_x= –1mA.

V_x=10*10³*(–1*10^-3)= –10V