 ## General Class Exam Question Pool- Subelement G-5

###### Subelement G-6           Subelement G-7          Subelement G-8          Subbelement G-9          Subelement G-0

SUBELEMENT G5 – ELECTRICAL PRINCIPLES [3 Exam Questions – 3 Groups

G5A - Reactance; inductance; capacitance; impedance; impedance matching

G5A01

What is impedance?

A. The electric charge stored by a capacitor

B. The inverse of resistance

C. The opposition to the flow of current in an AC circuit

D. The force of repulsion between two similar electric fields

~~

G5A02

What is reactance?

A. Opposition to the flow of direct current caused by resistance

B. Opposition to the flow of alternating current caused by capacitance or inductance

C. A property of ideal resistors in AC circuits

D. A large spark produced at switch contacts when an inductor is
de-energized

~~

G5A03

Which of the following causes opposition to the flow of alternating current in an inductor?

A. Conductance

B. Reluctance

D. Reactance

~~

G5A04

Which of the following causes opposition to the flow of alternating current in a capacitor?

A. Conductance

B. Reluctance

C. Reactance

~~

G5A05

How does an inductor react to AC?

A. As the frequency of the applied AC increases, the reactance decreases

B. As the amplitude of the applied AC increases, the reactance increases

C. As the amplitude of the applied AC increases, the reactance decreases

D. As the frequency of the applied AC increases, the reactance increases

~~

G5A06

How does a capacitor react to AC?

A. As the frequency of the applied AC increases, the reactance decreases

B. As the frequency of the applied AC increases, the reactance increases

C. As the amplitude of the applied AC increases, the reactance increases

D. As the amplitude of the applied AC increases, the reactance decreases

~~

G5A07

What happens when the impedance of an electrical load is equal to the output impedance of a power source, assuming both impedances are resistive?

A. The source delivers minimum power to the load

B. The electrical load is shorted

C. No current can flow through the circuit

D. The source can deliver maximum power to the load

~~

G5A08

Why is impedance matching important?

A. So the source can deliver maximum power to the load

B. So the load will draw minimum power from the source

C. To ensure that there is less resistance than reactance in the circuit

D. To ensure that the resistance and reactance in the circuit are equal

~~

G5A09

What unit is used to measure reactance?

B. Ohm

C. Ampere

D. Siemens

~~

G5A10

What unit is used to measure impedance?

A. Volt

B. Ohm

C. Ampere

D. Watt

~~

G5A11

Which of the following describes one method of impedance matching between two AC circuits?

A. Insert an LC network between the two circuits

B. Reduce the power output of the first circuit

C. Increase the power output of the first circuit

D. Insert a circulator between the two circuits

~~

G5A12

What is one reason to use an impedance matching transformer?

A. To minimize transmitter power output

B. To maximize the transfer of power

C. To reduce power supply ripple

~~

G5A13

Which of the following devices can be used for impedance matching at radio frequencies?

A. A transformer

B. A Pi-network

C. A length of transmission line

D. All of these choices are correct

~~

G5B - The Decibel; current and voltage dividers; electrical power calculations; sine wave root-mean-square (RMS) values; PEP calculations

G5B01

What dB change represents a two-times increase or decrease in power?

A. Approximately 2 dB

B. Approximately 3 dB

C. Approximately 6 dB

D. Approximately 12 dB

~~

G5B02

How does the total current relate to the individual currents in each branch of a purely resistive parallel circuit?

A. It equals the average of each branch current

B. It decreases as more parallel branches are added to the circuit

C. It equals the sum of the currents through each branch

D. It is the sum of the reciprocal of each individual voltage drop

~~

G5B03

How many watts of electrical power are used if 400 VDC is supplied to an 800 ohm load?

A. 0.5 watts

B. 200 watts

C. 400 watts

D. 3200 watts

~~

G5B04

How many watts of electrical power are used by a 12 VDC light bulb that draws 0.2 amperes?

A. 2.4 watts

B. 24 watts

C. 6 watts

D. 60 watts

~~

G5B05

How many watts are dissipated when a current of 7.0 milliamperes flows through 1.25 kilohms resistance?

A. Approximately 61 milliwatts

B. Approximately 61 watts

C. Approximately 11 milliwatts

D. Approximately 11 watts

~~

G5B06

What is the output PEP from a transmitter if an oscilloscope measures 200 volts peak-to-peak across a 50 ohm dummy load connected to the transmitter output?

A. 1.4 watts

B. 100 watts

C. 353.5 watts

D. 400 watts

~~

G5B07

What value of an AC signal produces the same power dissipation in a resistor as a DC voltage of the same value?

A. The peak-to-peak value

B. The peak value

C. The RMS value

D. The reciprocal of the RMS value

~~

G5B08  *** QUESTION REMOVED BY QPC  February 4, 2015****

G5B09

What is the RMS voltage of a sine wave with a value of 17 volts peak?

A. 8.5 volts

B. 12 volts

C. 24 volts

D. 34 volts

~~

G5B10

What percentage of power loss would result from a transmission line loss of 1 dB?

A. 10.9 percent

B. 12.2 percent

C. 20.5 percent

D. 25.9 percent

~~

G5B11

What is the ratio of peak envelope power to average power for an unmodulated carrier?

A. 0.707

B. 1.00

C. 1.414

D. 2.00

~~

G5B12

What would be the RMS voltage across a 50 ohm dummy load dissipating 1200 watts?

A. 173 volts

B. 245 volts

C. 346 volts

D. 692 volts

~~

G5B13

What is the output PEP of an unmodulated carrier if an average reading wattmeter connected to the transmitter output indicates 1060 watts?

A. 530 watts

B. 1060 watts

C. 1500 watts

D. 2120 watts

~~

G5B14

What is the output PEP from a transmitter if an oscilloscope measures 500 volts peak-to-peak across a 50 ohm resistive load connected to the transmitter output?

A. 8.75 watts

B. 625 watts

C. 2500 watts

D. 5000 watts

~~

G5C – Resistors, capacitors, and inductors in series and parallel; transformers

G5C01

What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding?

A. Capacitive coupling

B. Displacement current coupling

C. Mutual inductance

D. Mutual capacitance

~~

G5C02

What happens if you reverse the primary and secondary windings of a 4:1 voltage step down transformer?

A. The secondary voltage becomes 4 times the primary voltage

B. The transformer no longer functions as it is a unidirectional device

~~

G5C03

Which of the following components should be added to an existing resistor to increase the resistance?

A. A resistor in parallel

B. A resistor in series

C. A capacitor in series

D. A capacitor in parallel

~~

G5C04

What is the total resistance of three 100 ohm resistors in parallel?

A. 0.30 ohms

B. 0.33 ohms

C. 33.3 ohms

D. 300 ohms

~~

G5C05

If three equal value resistors in series produce 450 ohms, what is the value of each resistor?

A. 1500 ohms

B. 90 ohms

C. 150 ohms

D. 175 ohms

~~

G5C06

What is the RMS voltage across a 500-turn secondary winding in a transformer if the 2250-turn primary is connected to 120 VAC?

A. 2370 volts

B. 540 volts

C. 26.7 volts

D. 5.9 volts

~~

G5C07

What is the turns ratio of a transformer used to match an audio amplifier having 600 ohm output impedance to a speaker having 4 ohm impedance?

A. 12.2 to 1

B. 24.4 to 1

C. 150 to 1

D. 300 to 1

~~

G5C08

What is the equivalent capacitance of two 5.0 nanofarad capacitors and one 750 picofarad capacitor connected in parallel?

~~

G5C09

What is the capacitance of three 100 microfarad capacitors connected in series?

~~

G5C10

What is the inductance of three 10 millihenry inductors connected in parallel?

A. 0.30 henrys

B. 3.3 henrys

C. 3.3 millihenrys

D. 30 millihenrys

~~

G5C11

What is the inductance of a 20 millihenry inductor connected in series with a 50 millihenry inductor?

A. 0.07 millihenrys

B. 14.3 millihenrys

C. 70 millihenrys

D. 1000 millihenrys

~~

G5C12

What is the capacitance of a 20 microfarad capacitor connected in series with a 50 microfarad capacitor?

~~

G5C13

Which of the following components should be added to a capacitor to increase the capacitance?

A. An inductor in series

B. A resistor in series

C. A capacitor in parallel

D. A capacitor in series

~~

G5C14

Which of the following components should be added to an inductor to increase the inductance?

A. A capacitor in series

B. A resistor in parallel

C. An inductor in parallel

D. An inductor in series

~~

G5C15

What is the total resistance of a 10 ohm, a 20 ohm, and a 50 ohm resistor connected in parallel?

A. 5.9 ohms

B. 0.17 ohms

C. 10000 ohms

D. 80 ohms

~~

G5C16

Why is the conductor of the primary winding of many voltage step up transformers larger in diameter than the conductor of the secondary winding?

A. To improve the coupling between the primary and secondary

B. To accommodate the higher current of the primary

C. To prevent parasitic oscillations due to resistive losses in the primary

D. To insure that the volume of the primary winding is equal to the volume of the secondary winding

~~

G5C17
What is the value in nanofarads (nF) of a 22,000 pF capacitor?
A. 0.22 nF
B. 2.2 nF

C. 22 nF
D. 220 nF
~~

G5C18

What is the value in microfarads of a 4700 nanofarad (nF) capacitor?
A. 47 µF
B. 0.47 µF
C. 47,000 µF

D. 4.7 µF
~~