XX - SPECIAL-PURPOSE OP-AMP CIRCUITS

In document Basic Electronics (Page 90-103)

9. Initially, the closed-loop gain (Acl) of a Wien-bridge oscillator should be

A. Acl < 3 B. Acl > 3 C. 0 D. Acl 1

Answer: Option B

.

10. In an averaging amplifier, the input resistances are

A. equal to the feedback resistance

B. less than the feedback resistance

C. greater than the feedback resistance

D. unequal

Answer: Option C

11. A triangular-wave oscillator can consist of an op-amp comparator, followed by a(n)

A. differentiator B. amplifier C. integrator D. multivibrator

Answer: Option C

.

12. The ramp voltage at the output of an op-amp integrator

A. increases or decreases at a linear rate B. increases or decreases exponentially C. is always increasing and never decreasing D. is constant

Answer: Option A

.

13. A two-pole high-pass active filter would have a roll-off rate of

A. 40 dB/decade B. –40 dB/decade C. 20 dB/decade D. –20 dB/decade

Answer: Option B

XX - SPECIAL-PURPOSE OP-AMP CIRCUITS

1 .

Which circuit is known as a current-to-voltage converter?

A. a B. b

C. c D. d

Answer: Option A

.

2. When using an OTA in a Schmitt-trigger configuration, the trigger points are controlled by

A. the Iout

B. the IBIAS

C. the Vout

D. both Iout and IBIAS

Answer: Option D

.

3 .

Refer the given circuits. Which circuit is known as an OTA?

A. a B. b

C. c D. d

Answer: Option D

.

4.

This circuit is a setup for A. an antilog amplifier B. a constant-current source C. an instrumentation amplifier D. an isolation amplifier

Answer: Option C

.

5.

Which circuit is known as a voltage-to-current converter?

A. a B. b

C. c D. d

Answer: Option B

6. The primary function of the oscillator in an isolation amplifier is to

A. convert dc to high-frequency ac

B. convert dc to low-frequency ac

C. rectify high-frequency ac to dc

D.

produce dual-polarity dc voltages for the input to the demodulator

Answer: Option A

.

7.

Refer to Figure 20-2. This circuit is a setup for

A. an antilog amplifier

B. a constant-current source

C. an instrumentation amplifier

D. an isolation amplifier

Answer: Option B

.

8. An instrumentation amplifier has a high

A. output impedance B. power gain C. CMRR

D. supply voltage

Answer: Option C

.

9 .

This circuit is a setup for A. an antilog amplifier

B. a constant-current source

C. an instrumentation amplifier

D. an isolation amplifier

Answer: Option D

.

10. Circuits that shift the dc level of a signal are called

A. limiters B. clampers C. peak detectors D. dc converters

Answer: Option B 1

1 .

The voltage gain of an OTA can be calculated using the formula

A.

B.

C.

D.

Answer: Option B

.

12. In the classic three-op-amp instrumentation amplifier, the differential voltage gain is usually produced by the

A. first stage B. second stage C. mismatched resistors D. output op-amp

Answer: Option A

XXI - Measurement, Conversion and Control

1. What device is similar to an RTD but has a negative temperature coefficient?

A. Strain gauge B. Thermistor C. Negative-type RTD D. Thermocouple

Answer: Option B

.

2. The resistive change of a strain gauge

A. is based on the weight placed upon it, but can be many thousands of ohms B. is usually no more than 100

C. is based on the gauge factor, but is typically less than an ohm D. has a positive temperature coefficient

Answer: Option C

.

3. The silicon-controlled rectifier can be turned off A. by a negative gate pulse

B. by forced commutation C. with the off switch

D. when the breakover voltage is exceeded

Answer: Option B

.

4. The output voltage of a typical thermocouple is A. less than 100 mV

B. greater than 1 V

C. Thermocouples vary resistance, not voltage.

D. None of the above

Answer: Option A

.

5. The connections to a thermocouple

A. can produce an unwanted thermocouple effect, which must be compensated for B. produce an extra desirable thermocouple effect

C. must be protected, since high voltages are present

D. produce an extra desirable thermocouple effect and must be protected, since high voltages are present

Answer: Option A

6. What is the

zero-voltage switch used for?

A.

To reduce radiation of high

To provide power to a

Answer: Option A

.

7. Temperature sensing can be achieved by the use of A. thermocouples

B. RTDs C. thermistors D. All of the above

Answer: Option D

.

8. The purpose of compensation for a thermocouple is A. to decrease temperature sensitivity

B. to increase voltage output

C. to cancel unwanted voltage output of a thermocouple

D. used for high-temperature circuits

Answer: Option C

.

9. The change in value of an analog signal during the conversion process produces what is called the

A. quantization error B. resolution error C. Nyquist error D. sampling error

Answer: Option A

.

10. Which of the following performance specifications applies to a sample-and-hold circuit?

A. Aperture time B. Aperture droop C. Feedback D. Acquisition jitter

Answer: Option A

11. RTDs are typically connected with other fixed resistors A. in a pi configuration

B. in a bridge configuration C. and variable resistors

D. and capacitors in a filter-type circuit

Answer: Option B

.

12. Holding current for an SCR is best described as A. the minimum current required for turn-off B. the current required before an SCR will turn on

C. the amount of current required to maintain conduction

D. the gate current required to maintain conduction

Answer: Option C

.

13. What is the moving part of a linear variable differential transformer?

A. Primary B. Secondary

C. Diaphragm D. Core

Answer: Option D

XXII - Resistance and Power

1. The resistivity of copper is:

A. 9.9 B. 10.7 C. 16.7 D. 17.0

Answer: Option B

.

2. How do fixed resistors usually fail?

A. slowly over time B. by increasing their value C. by becoming an open circuit

D. by increasing their value and becoming an open circuit

Answer: Option C

.

3. With Ohm's law, if voltage increases and resistance stays the same:

A. current remains the same B. power decreases

C. current increases D. resistance decreases

Answer: Option C

.

4. Which formula shows a direct proportionality between power and voltage?

A. V = IR B. P = VI C. P = IR D. I = V/R

Answer: Option B

.

5. With 1 mA of current, what wattage rating should a 470 ohm resistor have?

A. 1/4 watt B. 1/2 watt C. 1 watt D. 2 watts

Answer: Option A

6. How is a 3.9 k resistor color-coded?

A. red, white, red, gold B. red, green, orange, silver C. orange, white, red, gold D. orange, green, orange, silver

Answer: Option C

.

7. What resistor type is found in SIPs and DIPs?

A. metal film B. wirewound C. metal oxide D. thick film

Answer: Option D

.

8. Ohm's law is not:

A. V = IR B. I = V/R C. R = IV D. R = V/I

Answer: Option C

.

9. What are the two major categories for resistors?

A. low and high ohmic value B. commercial and industrial C. low and high power value D. fixed and variable

Answer: Option D

.

10.

How many connections does a potentiometer have?

A. 1 B. 2

C. 3 D. 4

Answer: Option C

A potentiometer uses three connections, as opposed to a rheostat, which only employs two. Having three connections allows the potentiometer to vary voltage.

Both the potentiometer and the rheostat are classified as variable resistors.

11.

What current is flowing in the circuit?

A. 288 kA B. 2 kA C. 50 mA D. 500 A

Answer: Option D

.

12. The six basic forms of energy are:

A. light, sun, magnetic, chemical, electrical, and mechanical

B. electrical, mechanical, light, heat, magnetic, and chemical

C. electrical, mechanical, sun, heat, chemical, and light

D. potential, sun, light, chemical, electrical, and mechanical

Answer: Option B

.

13. How much energy is stored if 6.24 x 1018 electrons are stored in 4 volts?

A. 4 joules

B. 1.56 x 1018 electrons C. 1.56 coulombs D. 2.496 x 1019 electrons

Answer: Option A

.

14. With Ohm's law:

A. current is inversely proportional to resistance B. resistance is directly proportional to voltage C. voltage is indirectly proportional to power D. current is directly proportional to resistance

Answer: Option A

.

15. Power is defined as:

A. the rate at which energy is used B. watts

C. energy

D. the rate at which energy is generated

Answer: Option A

16. What is the most commonly used conductor in electronics?

A. aluminum B. copper

C. gold D. silver

Answer: Option B

.

17. With Ohm's law, no change in resistance means that current and voltage will be:

A. directly proportional B. unable to produce energy C. the same

D. inversely proportional

Answer: Option A

.

18. A potentiometer has how many leads?

A. 1 B. 2

C. 3 D. 4

Answer: Option C

.

19. What is the ratio of 13 to 47 expressed in percent?

A. 2.76% B. 27.7%

C. 3.60% D. 36.1%

Answer: Option B

.

20. What happens to current and resistance if the voltage doubles?

A. Current doubles and resistance doubles.

B. Current doubles and resistance is halved.

C. Current remains the same and resistance doubles.

D. Current doubles and resistance remains the same.

Answer: Option D

21. One problem with mechanically variable resistors is noticeable in audio circuits as:

A. scratchy noise B. lack of bass response C. variable volume

D. too much treble response

Answer: Option A

.

22. A color code of orange, orange, orange is for what ohmic value?

A. 22 kilohms B. 3300 ohms C. 44000 ohms D. 33 kilohms

Answer: Option D

.

23. A conductor's cross-sectional area in circular mils

for inch is:

A. 500 cmils B. 100,000 cmils C. 1,000,000 cmils D. 500,000,000 cmils

Answer: Option C

.

24. If a variable resistor's resistance varies in a nonuniform manner as the shaft is moved, it is considered to be:

A. linear B. defective C. not wirewound D. tapered

Answer: Option D

.

25. Power is measured in units of:

A. joules x charge B. joules/work C. joules x voltage D. joules/time

Answer: Option D

26. How many basic types of resistors exist?

A. 1 B. 2

C. 3 D. 4

Answer: Option B

.

27. With a complex circuit, a supply source senses:

A. open circuit components

B. when voltages need to be increased C. only a single resistive connection D. when complex currents are needed

Answer: Option C

.

28. How many ohms of resistance allows a current of 720 A to flow when 3.6 kV is applied?

A. 200 n B. 5 k C. 200 k D. 5 M

Answer: Option D

.

29. Which is the most important step utilized when measuring resistors?

A. use the highest possible scale B. keep test leads short

C. zero the meter before using D. remove power from the circuit

Answer: Option D

.

30. Components designed to oppose the flow of current are called:

A. insulators B. conductors C. resistors D. heat exchangers

Answer: Option C

31. How many amps are used by a 100 watt, 120 volt light bulb?

A. 1.2 amps B. 12000 amps C. 830 mA D. 12 amps

Answer: Option C

.

32. The source is 24 volts and the load resistance is 100 . What is the load current?

A. 2.4 A B. 240 mA C. 24 mA D. 2.4 mA

Answer: Option B

.

33. Resistors are identified as to wattage by:

A. size B. color code C. types of materials

D. internal construction

Answer: Option A

.

34. What type of resistors have a tolerance rating of 5% or greater?

A. precision B. SIP

C. general-purpose D. wirewound

Answer: Option C

.

35. Resistor tolerance is either printed on the component, or is provided by:

A. keyed containers B. size

C. color code D. ohmmeter reading

Answer: Option C

36. How many connections does a rheostat have?

A. 1 B. 2

C. 3 D. 4

Answer: Option B

.

37. What are the parts of a rheostat?

A. wiper and resistor track B. solenoid and armature C. contact and wire wound D. center tape and wiper

Answer: Option A

.

38. The load resistance increases. How will the load current change?

A. vary

B. remain constant C. increase D. decrease

Answer: Option D

.

39. What is the power dissipated by a 1.2 k resistor with 12 volts across it?

A. 12 A B. 1.2 A C. .12 A D. 12 mA

Answer: Option C

.

40. How many joules of energy will a 10 W lamp dissipate in one minute?

A. 10 joules B. 60 joules C. 600 joules D. 3600 joules

Answer: Option C

41. Which type of test equipment is used to measure resistors?

A. ohmmeter B. ammeter C. voltmeter D. watt meter

Answer: Option A

.

42. Resistance is:

A. the opposition to current flow accompanied by the dissipation of heat

B. symbolized by R, measured in ohms, and directly proportional to conductance C. directly proportional to current and voltage

D. represented by the flow of fluid in the fluid circuit

Answer: Option A

.

43. Electrical equipment is protected against excessive current by a(n):

A. fusible wire link

B. insulated glass container C. metal ended coil D. circuit opener

Answer: Option A

.

44. If resistance decreases, then current will:

A. decrease B. increase

C. remain the same D. double

Answer: Option B

.

45. A wire with a smaller cross-sectional area will produce:

A. less heat

B. more conductance C. less resistance D. more heat

Answer: Option D

46. A 22-gauge wire will have a diameter in mils of:

A. 10.03 B. 22.35

C. 45.26 D. 71.96

Answer: Option B

.

47. The word work means that:

A. energy has been transferred B. it is inversely related to energy C. no energy has been transferred D. work and energy are not related

Answer: Option A

.

48. A good fuse will have:

A. zero ohms resistance B. a medium resistance

C. a high resistance D. an infinite resistance

Answer: Option A

.

49. What property does an incandescent lamp possess?

A. cold resistance B. hot resistance C. ballast resistance

D. both cold and hot resistance

Answer: Option D

.

50. One advantage of a carbon film resistor over a carbon composition resistor is:

A. less circuit noise B. smaller size C. higher wattage D. poor tolerance

Answer: Option A

51. If a metallic conductor has a positive temperature coefficient of resistance, then:

A. as temperature increases, resistance decreases B. as current increases, resistance decreases C. as voltage increases, current increases D. as temperature increases, resistance increases

Answer: Option D

.

52. What value of a 1.3 k resistor as measured by a digital voltmeter would be considered within tolerance?

A. 1234 B. 1235 C. 1366 D. 1367

Answer: Option B

.

53. If a calculator display was "0.00263," what would this answer be in percent?

A. 0.026% B. 0.26%

C. 2.63% D. 26.3%

Answer: Option B

.

54. A 33 k resistor with a 20% tolerance checks out as ok with which of the following ohmmeter readings?

A. 26400 ohms B. 24183 ohms C. 6600 ohms D. 39970 ohms

Answer: Option A

.

55. For P = V2/R, a decrease in resistance should produce:

A. a decrease in power B. an increase in ohms C. an increase in power

D. a decrease in current

Answer: Option C

56. After a lamp is turned on, its filament resistance will change to become:

A. less resistive B. cooler C. brighter D. more resistive

Answer: Option D

.

57. Wirewound resistors are usually used in circuits that have:

A. high current

B. negative temperature coefficients C. low power

D. high voltage

Answer: Option A

.

58. How is power dissipated in a resistor?

A. by resistance B. by voltage C. by current D. by heat

Answer: Option D

.

59. Resistance in a circuit is:

A. opposition to current B. opposition to voltage C. the same as current D. the same as voltage

Answer: Option A

.

60. The unit designator for resistance value is the:

A. ampere B. ohm

C. volt D. watt

Answer: Option B

61. One ampere of current flowing through one ohm of resistance is equal to:

A. 1 horsepower B. 1 Btu C. 1 watt D. 1 joule

Answer: Option C

.

62. Good insulators:

A. have few electrons in their outer shells B. have a large dielectric strength C. have a small breakdown voltage D. have many electrons in the nucleus

Answer: Option B

XXIII - ALTERNATING CURRENT VS DIRECT

In document Basic Electronics (Page 90-103)