天津商业大学07-08学年第1学期电路期末考试题(期末)

scores
signature
-
7V
+ 2A 1A
°
10Ω
I
°+
Refer to the circuit as shown in the Fig. When R = 2 Ω , the power supplied by the dependent source is P= the resistance R should be W; If the power absorbed by the dependent source is 4 W, the value of
4Ω 4Ω
°
U1 4Ω 4Ω
U1
100 V
R 20 V
° -4-
2007-2008 学年第一学期
3、(3 scores) the circuit is shown in the Fig.. Find the voltage between terminals a-b. then U ab is A. 80 V
+200V
°
信息工程学院《电路》 （课程）试卷 A
— — — 班— 级 ： 装 订 线 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — （请考生注意：本试卷共 4 页）
1Ω
1V 1Ω
1．(7 scores) for the circuit as shown in the Fig. Using KCL and KVL, find the current I , the voltage U , and the power absorbed by the element X respectively.
4Ω
1Ω 2A
I2
I1 1Ω 4A
1Ω 2A 1Ω
4A
3Ω I
6V
2Ω
X
U
2. (6 scores) Use equivalent transformation to simplify the following circuit. Known that R L = 4Ω , calculate the current I L .
B. 0 V
C. -80 V
°
D. -50 V
Answer (
)
+200V
试卷来源：题库 送卷人:王光艳 打印：李海丰 乔凤云 校对：滕建辅 题 得 阅 目 分 卷
Ⅰ Ⅱ Ⅲ Ⅳ 总 分
40kΩ
5Ω
20kΩ
°a
b° 5kΩ
° -50V
60kΩ -100V°
姓 名 ：
Ⅰ. In the following problems, select the correct answer (only one is correct). (6 problems, 19 scores) 1、(2 scores) Refer to the circuit, assume that R 、 U S 、 I S are all greater than zero. Consider the power supplied or absorbed by each element: A. the resistor absorbs power, and the current and voltage sources supply power simultaneously. B. the resistor and the voltage source absorb power simultaneously, and only the current source supplies power. C. the resistor and the current source absorb power simultaneously, and only the voltage source supplies power. D. the resistor absorbs power, while the current source supplies power. Power absorbed or supplied by the voltage source can not be determined. Answer ( ) scores signature
1 3 4

2Ω i L 6V
2H t=0
° °
2F
5
6、(6 scores) For the circuit as shown in the Fig. The switch has been in position a for a long time. At t = 0 , it switched to position b. The complete response of uC (t ) for t>0 is____________________________
1Ω
+ 3V -
U
-
Ω, 1Ω R 4V 2I
5、(6 scores) the circuit has been in steady state before t = 0 − . The switch is opened at t = 0 . (1) Write the differential equation in terms of i L for t > 0 . (2) Determine the initial conditions.
2
6
The steady-state response is ___________
_______,
The transient response is _______________________, 3、(3 scores) Assuming that the zero-input response of a first-order circuit is uCx = 5e
2A
4．(7 scores) Use nodal analysis to calculate U x and I x of the following circuit.
2Ω Ux
1 4Ω
4Ω
2 2V Ix
2Ω
2Ω
6V
1Ω 3U x 3
4Ω 8V
8V
IL RL
4Ω 2A
-3-
Ⅳ comprehensive calculation problems (3 problems, 29 scores)
3 Ω 40 1 C. Ω 7
A.
°
Answer ( ) 5、 (4 scores) Assume that the voltage of a first-order circuit decreases exponentially, the voltage is 15V at t = 0 , and is 6V at t = 2 seconds. Then the time constant τ of the circuit is A. 0.458s B. 2.18s C. 0.2s D. 0.1s Answer ( ) 6、 (4 scores) For the circuit shown below, N is a linear active network， when U S = 10 V I = 2 A； when U S = 20 V， I = 6 A；If we let U S = −20 V, then the value of I is
1．( 9 scores) Use superposition theorem to calculate the power supplied by the dependent source.
2Ω 2U 1Ω U 4Ω 2V 1A
u 2
iS A iL 2 1
iS 4Ω
u
4H
Ｏ
2
t s
2. (10 scores ) For the circuit, find (1) the value of R that will absorb maximum power from the circuit. (2) the value of the maximum power.
t − 3 − t 3
The zero-input response is___________________，
V ，and the zero-state
The zero-state response is _____________________.
t=0
response is uCx = 2 (1 − e )V . When the value of the excited voltage source is changed to three times as the original value, the complete response will be uC ' (t ) = _______________。 4、(4 scores) For the circuit, calculate the parameters of the Thevenin equivalent circuit. The two parameters are U OC = V， R0 = Ω。
I
B. 7 Ω
40 D. Ω 3
12S
Answer (
)
US
N
R
R
°
3S
4S
2S
A. -6 A B. -10 A
C. 8 A
D. -8 A