### Computer Science - Electronic Principles MCQs Part 3

1. Which one of the following statements is true for the voltages in a series RL circuit?

A.
The total voltages is equal to the sum of the voltages across the resistance and inductance
B.
The voltage always has the same amplitude and phase for every part of the circuit
C.
The total voltage is less than the sum of the voltages across the resistance and inductance
D.
The total voltage lags the total current by less than 90
E.
None of the above

2. The core of an electromagnet is said to be in saturation when:

A.
the core is permitted to move freely within the coil
B.
an increase in current through the coil causes no further increase in the mmf
C.
frequent changes in the direction of current through the coil causes heating effects in the core material
D.
changing the polarity of the current in the coil changes the polarity of the magnetic field around the core
E.
None of the above

3. As the temperature increases, the current gain

A.
increases
B.
decreases
C.
contant
D.
can be any of the above
E.
None of the above

4. Assuming 100% efficiency, what is the power being consumed at the secondary winding of the transformer described in question 91?

A.
200 W
B.
1000 W
C.
20 W
D.
100 W
E.
None of the above

5. Doubling the diameter of the coil in an inductor:

A.
multiplies the value of inductance by two
B.
reduces the value of inductance by one-half
C.
reduces the value of inductance by one-fourth
D.
multiplies the value of inductance by four
E.
None of the above

6. Which one of the following statements is true for the impedance of a series RC circuit?

A. The impedance is greater than the sum of the resistance and capacitive reactance
B. The impedance is equal to the sum of the resistance and capacitive reactance
C. The impedance is greater than either the resistance or capacitive reactance but less than their sum
D. The impedance is less than the sum of the resistance and capacitive reactance
E. None of the above

7. If a transistor operates at the middle of the load line, an increase in the current gain will move the Q point

A. down
B. up
C. nowhere
E. None of the above

8. What is the turns ratio of a power transformer that shows 50 V at its secondary winding when you apply 150 V to its primary winding?

A. 1/4
B. 1/3
C. 2
D. 3
E. None of the above

9. What is the inductive reactance of a 0.1-H coil that is operating at 1000 Hz?

A. 100 Ohm
B. Less than 1 Ohm
C. 628 Ohm
D. 444 Ohm
E. None of the above

10. Which one of the following is a statement of KirchhofFs voltage law?

A. The total voltage in a parallel circuit is less than the value of the smallest voltage
B. The algebraic sum of voltages in a loop is equal to zero
C. The voltage drop across a resistance is proportional to the value of resistance and the amount of current flowing through it
D. The algebraic sum of voltages entering and leaving a point is equal to zero
E. None of the above

11. What is the impedance of a circuit composed of a 100 ohm resistor connected in parallel with a capacitor that has a reactance of 100 ohm?

A. 60 Ohm
B. 99.3 Ohm
C. 250 Ohm
D. 70.7Ohm
E. None of the above

12. Current can flow through a normally open push button switch as long as:

A. you are pressing the button
B. you are not pressing the button
C. its contact remain open
D. its contact remain open
E. None of the above

13. Doubling the operating frequency of a purely capacitive circuit:

A. has no effect on the total circuit current
B. doubles the amount of total current
C. cuts the total current by one-half
D. thrice the amount of total current
E. None of the above

14. How much current flows through a 0.02 micro F capacitor that is operating from a 12-V ac, 100-Hz source?

A. 0.151 mA
B. 157 raA
C. 0.995 mA
D. 2.02 A
E. None of the above

15. An unloaded zener regulator has a source voltage of 20 V, a series resistance of 330 W, and a zener voltage of 12 V, What is the Zener current?

A. 28.4 mA
B. 24.2 mA
C. 34.4 mA
D. 68.4 mA
E. None of the above

16. The total capacitance of a series capacitor circuit is:

A. equal to the sun of the individual capacitive-reactance values
B. equal to the sum of the individual capacitance values
C. equal to the source voltage divided by total current
D. less than the value of the smallest capacitor
E. None of the above

17. Assuming 100% efficiency, what is the power being applied to the primary winding of the transformer described in the above question?

A. 200 W
B. 1000 W
C. 20 W
D. 100 W
E. None of the above

18. To get the Thevenin voltage, you have to

C. Short the voltage source
D. Open the voltage source
E. None of the above

19. Which one of the following properties of a magnetic circuit can be directly compared to resistance in an electrical circuit?

A. Reluctance
B. Permeability
C. Permeance
D. Retentivity
E. There is no valid comparison

20. How many types of flow are there in a semiconductor?

A. 0
B. 1
C. 2
D. 4
E. None of the above

21. When operating above its resonant frequency, a parallel RLC circuit has the characteristics of a:

A. parallel RL circuit
B. parallel RC circuit
C. parallel RLC circuit operated above its resonant frequency
D. purely resistive circuit
E. None of the above

22. Doubling the operating frequency of an inductive circuit:

A. has no effect on the inductive reactance
B. doubles the amount of inductive reactance
C. multiplies the inductive reactance by 6.28
D. cuts the inductive reactance in half
E. None of the above

23. A circuit has a Norton current of 10 mA and a Norton resistance of 10 kW. What is the Thevenin circuit?

A. 1000 V and a series resistance of 10 k Ohm
B. 100 V and a parallel resistance of 10 k Ohm
C. 100 V and a series resistance of 10 k Ohm
D. 1000 V and a parallel resistance of 10 kOhm
E. None of the above

24. Which one of the following statements is true?

A. Power dissipation of a pure capacitor increases with operating frequency
B. Power dissipation of a pure capacitor decreases with operating frequency
C. There is no meaningful relationship between the power dissipation of a pure capacitor and its operating frequency
D. All of the above
E. None of the above

25. A power transformer steps 100 V down to 10 V. If the current in its primary winding is 2 A, what is the current in the secondary winding?

A. 50 A
B. 12 A
C. 5 A
D. 20 A
E. None of the above

26. If a load resistance is 1 kW, a stiff voltage source has a resistance of

A. At least 10 Ohm
B. less than 10 Ohm
C. More than 100 k Ohm
D. Less than 100 k Ohm
E. None of the above

27. A typical light switch in your home is a:

A. knife switch
B. toggle switch
C. rotary switch
D. momentary push button switch
E. None of the above

28. Suppose the voltage from a power outlet is 120 Vrms. What is the peak voltage?

A. 100 V
B. 120 V
C. 170 V
D. 180 V
E. None of the above

29. A device that converts thermal energy to electrical energy is called a:

A. thermocouple
B. solar cell
C. chemical cell
D. piezoelectric devices
E. None of the above

30. How much power is being dissipated by a 1000 W resistance that has 25 V applied to it?

A. 0.24 W
B. 0.625 W
C. 80 W
D. 325 kW
E. None of the above

31. A device that converts chemical energy to electrical energy is called a:

A. solar cell
B. thermocouple
C. chemical cell
D. electric device
E. None of the above

32. Suppose the peak value of a sinusoidal voltage is 50 V. What is the rms value?

A. 37.4 V
B. 35.4 V
C. 38.74 V
D. 30.4 V
E. None of the above

33. What is the difference between a conductor and an insulator?

A. A conductor allows current to flow much easier than an insulator does
B. An insulator has an excessive number of free electrons, while a conductor has a few free electrons or none at all
C. An insulator allows current to flow much easier than a conductor does
D. The difference between conductors and insulators depends on how they are used
E. None of the above

34. A circuit has two different voltage sources that are connected in a series-aiding form. If the sources are rated at 6 V and 9 V, what is the total source voltage?

A. 15 V
B. 16 V
C. 7.5 V
D. 8 V
E. None of the above

35. At room temperature an intrinsic semiconductor has

A. a few free electrons and holes
B. many holes
C. many free electrons
D. No holes
E. None of the above

36. If the base supply voltage increases, the Q point moves

A. down
B. up
C. nowhere
E. None of the above

37. Positive ions are atoms that have

A. Gained a proton
B. Lost a proton
C. Gained an electron
D. Lost an electron
E. None of the above

38. Which one of the following is a statement of Kirchhoffs current law?

A. The current through a resistance is proportional to the value of resistance and the IR drop across it
B. The total current in a parallel circuit is less than the value of the smallest current
C. The algebraic sum of currents in a loop is equal to zero
D. The algebraic sum of currents entering and leaving a point is equal to zero
E. None of the above

39. Which one of the following statements is true?

A. inductive reactance decreases with operating frequency
B. inductive reactance is at a maximum for dc source voltages
C. inductive reactance increases with operating frequency
D. There is no meaningful relationship between inductive reactance and operating frequency
E. None of the above

40. A zener diode has a voltage of 10 V and a current of 20 mA. What is the power dissipation?

A. 200 mW
B. 300 mW
C. 20 mW
D. 10 mW
E. None of the above

41. Which one of the following phrasers best describes flux density?

A. The concentration of lines of magnetic force
B. The rate of change of the number of lines of magnetic force
C. The opposition to a build-up of magnetic fields
D. The force that maintains lines of force
E. None of the above

42. Which is the most widely used semiconductor?

A. Copper
B. Silicon
C. Germanium
D. All of the above
E. None of the above

43. The transistor has a current gain of 175. If the base current is 0.1 mA, what is the collector current?

A. 1750 mA
B. 17.5 mA
C. 175 mA
D. 1.75 mA
E. None of the above

44. An intrinsic semiconductor has some holes in it at room temperature. What causes these holes?

A. Doping
B. Valence electrons
C. Free electrons
D. Thermal energy
E. None of the above

45. Which one of the following statements is true?

A. Power dissipation of a pure inductor decreases with operating frequency
B. Power dissipation of a pure inductor is at a maximum for dc source voltages
C. Power dissipation of a pure inductor increases with operating frequency
D. There is no meaningful relationship between the power dissipation of a pure inductor and its operating frequency
E. None of the above

46. An audio transformer has a turn ratio of 9, What is its impedance ratio?

A. 81
B. 85
C. 6
D. 9
E. None of the above

47. Which one of the following statements is true?

A. The secondary voltage for a step-down power transformer is greater than the primary voltage
B. The secondary current for a step-down power transformer is greater than the primary voltage
C. Parallel RLC circuit operated below its resonant frequency
D. purely resistive circuit
E. None of the above

48. How many protons does the nucleus of a silicon atom contain?

A. 4
B. 29
C. 14
D. 48
E. None of the above

49. A circuit has two different voltage sources that are connected in a series-opposing form. If the sources are rated at 6 V and 9 V, what is the total source voltage?

A. 3 V
B. 16 V
C. 7.5 V
D. 8 V
E. None of the above

50. The emitter diode is usually

A. Forward-biased
B. Reverse-biased
C. Nonconducting
D. Operating in the breakdwon region
E. None of the above