Key Topic 18: Calculations

Question 1

3-18B1: What is the magnitude of the impedance of a series AC circuit having a resistance of 6 ohms, and inductive reactance of 17 ohms, and zero capacitive reactance?

A. 6.6 ohms.
B. 11 ohms.
C. 18 ohms.
D. 23 ohms.

Answer 1

C. 18 ohms.

Question 2

3-18B2: A 1-watt, 10-volt Zener diode with the following characteristics: Imin = 5 mA; Imax = 95 mA; and Z = 8 ohms, is to be used as part of a voltage regulator in a 20V power supply. Approximately what size current-limiting resistor would be used to set its bias to the midpoint of its operating range?

A. 100 ohms.
B. 200 ohms.
C. 1 kilohms.
D. 2 kilohms.

Answer 2

B. 200 ohms.

Question 3

3-18B3: Given a power supply with a no load voltage of 12 volts and a full load voltage of 10 bolts, what is the percentage of voltage regulation?

A. 17%
B. 80%
C. 20%
D. 83%

Answer 3

C. 20%

Question 4

3-18B4: What turns ratio does a transformer need in order to match a source impedance of 500 ohms to a load of 10 ohms?

A. 7.1 to 1.
B. 14.2 to 1.
C. 50 to 1.
D. None of these.

Answer 4

A. 7.1 to 1.

Question 5

3-18B5: Given a power supply with a full load voltage of 200 volts and a regulation of 25%, what is the no load voltage?

A. 150 volts.
B. 160 volts.
C. 240 volts.
D. 250 volts.

Answer 5

D. 250 volts.

Question 6

3-18B6: What is the conductance (G) of a circuit if 6 amperes of current flows when 12 volts DC is applied?

A. 0.25 Siemens (mhos).
B. 0.50 Siemens (mhos).
C. 1.00 Siemens (mhos).
D. 1.25 Siemens (mhos).

Answer 6

B. 0.50 Siemens (mhos).