Review the following concepts if needed:

**Alternating Current Practice Test**

A good score is eight correct. Answers are given at the end.

1. Approximately how many radians are in a quarter of a cycle?

(a) 0.7854

(b) 1.571

(c) 3.142

(d) 6.284

2. Refer to Fig. 13-18. Suppose that each horizontal division represents 1.0 ns (1.0 × 10 ^{−9} s) and that each vertical division represents 1 mV (1.0 × 10 ^{−3} V). What is the approximate rms voltage? Assume the wave is sinusoidal.

(a) 4.8 mV

(b) 9.6 mV

(c) 3.4 mV

(d) 6.8 mV

3. In the wave illustrated by Fig. 13-18, given the same specifications as those for the previous problem, what is the approximate frequency of this wave?

(a) 330 MHz

(b) 660 MHz

(c) 4.1 × 10 ^{9} rad/s

(d) It cannot be determined from this information.

4. In the wave illustrated by Fig. 13-18, what fraction of a cycle, in degrees, is represented by one horizontal division?

(a) 60

(b) 90

(c) 120

(d) 180

5. The maximum instantaneous current in a fluctuating dc wave is +543 mA over several cycles. The minimum instantaneous current is +105 mA, also over several cycles. What is the peak-to-peak current in this wave?

(a) 438 mA

(b) 648 mA

(c) 543 mA

(d) It cannot be calculated from this information.

6. The pk-pk voltage in a square wave is 5.50 V. The wave is ac, but it has a dc component of +1.00 V. What is the instantaneous voltage?

(a) More information is needed to answer this question.

(b) +3.25 V

(c) −1.25 V

(d) +1.00 V

7. Given the situation in the preceding question, what is the average voltage?

(a) More information is needed to answer this question.

(b) +3.25 V

(c) −1.25 V

(d) +1.00 V

8. Suppose that there are two sine waves having identical frequency and that their vector representations are at right angles to each other. What is the difference in phase?

(a) More information is needed to answer this question.

(b) 90°

(c) 180°

(d) 2 *π* rad

9. A square wave is a special form of

(a) sine wave.

(b) sawtooth wave.

(c) ramp wave.

(d) rectangular wave.

10. An ac wave has a constant frequency *f* . Its peak voltage *V* _{pk} is doubled. What happens to the period *T* ?

(a) It doubles to *2T* .

(b) It is reduced to *T* /2.

(c) It is reduced to 0.707 *T* .

(d) It remains at *T* .

**Answers**

1. b

2. c

3. a

4. c

5. a

6. a

7. d

8. b

9. d

10. d

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