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 Circuit Theorems in AC Analysis Multiple Choice

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1 .

The coil current in the above figure is [Hint]

 900° mA 98024° mA 98.524° mA 4090° mA

2 .       Referring to Problem 1, what is the current through L if its value is changed to 2.6 mH? [Hint]

 98.524° mA 98024° mA 600° mA 660° mA

3 .

Determine VTH for the circuit external to RL in the above figure. [Hint]

 13563.4° V 13.563.4° V 13.50° V 1350° V

4 .       Referring to Problem 3, determine VTH when R1 is 180 and XL is 90 . [Hint]

 13563.4° V 13.563.4° V 12.20° V 1220° V

5 .

For the circuit shown in the above figure, determine the Thevenin voltage as seen by RL. [Hint]

 0.57416.7° V 5.7416.7° V 0.574 -16.7° V 5.74-16.7° V

6 .       Referring to Problem 5, determine VTH if R1 is changed to 3.3 k. [Hint]

 0.57416.7° V 4.6316.7° V 4.6339.5° V 0.46339.5° V

7 .       In applying the superposition theorem, [Hint]

 the sources are considered one at a time with all others replaced by their internal impedance all sources are considered independently all sources are considered simultaneously the sources are considered one at a time with all others replaced by their internal resistance

8 .       The Thevenin equivalent voltage is [Hint]

 equal to the source voltage the same as the load voltage the open circuit voltage none of the above

9 .

For the above figure, find VTH for the circuit external to RL. [Hint]

 4.6951.3° V 4.6938.7° V 46938.7° mV 60° V

10 .       Referring to Problem 9, L [Hint]

 must be in parallel with RL must be placed in parallel with VS must have a reactance equal to XC has no effect on the result

11 .       Referring to Problem 9, what is VTH if VS = 12ang;0° V? [Hint]

 4.6938.7° V 9.3838.7° V 120° V 60° V

12 .

Referring to the above figure, find ZTH for the part of the circuit that is external to RL. [Hint]

 12921.4° 43.768.6° 43.721.4° 12.968.6°

13 .       Referring to Problem 12, what is ZTH if R1 is changed to 220 ? [Hint]

 22512.1° 22577.9° 4677.9° 4612.1°

14 .

Referring to the above figure, determine ZTH as seen by RL. [Hint]

 1444-48.5° 4176 -73.3° 956 -48.5° 1444 -73.3°

15 .       Referring to Problem 14, determine ZTH as seen by RL if R1 is changed to 3.3 k. [Hint]

 1488-70.7° 3859 -31.2° 5180 -50.5° 1828-50.2°

16 .       If two currents are in the same direction at any instant of time in a given branch of a circuit, the net current at that instant [Hint]

 is zero is the sum of the two currents is the difference between the two currents cannot be determined

17 .       The two basic components of a Thevenin equivalent ac circuit are [Hint]

 the equivalent voltage source and the equivalent series impedance the equivalent voltage source and the equivalent series resistance the equivalent voltage source and the equivalent parallel impedance the equivalent voltage source and the equivalent parallel resistance

18 .

For the circuit shown in the above figure, determine ZTH for the portion of the circuit external to RL. [Hint]

 66.7 -33.7° k 6.67-333.7° k 14.4 -56.3° k 1.44 -33.7° k

19 .       Referring to Problem 18, find ZTH if R is 15 k and RL is 38 k. [Hint]

 89.82 -51.3° k 19.2 -38.3° k 9.38-51.3° k 180 -38.3° k

20 .       Referring to Problem 18, find ZTH if VS is 180° V. [Hint]

 9.82 -51.3° k 9.38-51.3° k 180 -38.3° k 19.2 -38.3° k

21 .       Norton's theorem gives [Hint]

 an equivalent current source in parallel with an equivalent impedance an equivalent current source in series with an equivalent impedance an equivalent voltage source in parallel with an equivalent impedance an equivalent voltage source in series with an equivalent impedance

22 .       The Norton equivalent current is [Hint]

 the current through the load the open-current from the source the short circuit current none of the other choices is correct

23 .       In order to get maximum power transfer from a capacitive source, the load must [Hint]

 have a capacitive reactance equal to circuit resistance have an impedance that is the complex conjugate of the source impedance be as capacitive as it is inductive none of the other choices is correct

24 .

Determine the frequency at which the maximum power is transferred from the amplifier to the speaker in the above figure. [Hint]

 1,027 Hz 10,270 Hz 6,330 Hz 63,330 Hz

25 .       Referring to Problem 24, how much power, in watts, is delivered to the speaker at the determined frequency if VS = 4.5 VRMS? [Hint]

 226 mW 2.26 mW 4.24 mW 424 mW

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