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Ham General 2015-2019 > SUBELEMENT G5 – ELECTRICAL PRINCIPLES > Flashcards

SUBELEMENT G5 – ELECTRICAL PRINCIPLES Flashcards

1
Q

G5A01 (C)

What is impedance?

A

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

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2
Q

G5A02 (B)

What is reactance?

A

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

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3
Q

G5A03 (D)

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

A

D. Reactance

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4
Q

G5A04 (C)

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

A

C. Reactance

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5
Q

G5A05 (D)

How does an inductor react to AC?

A

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

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6
Q

G5A06 (A)

How does a capacitor react to AC?

A

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

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7
Q

G5A07 (D)
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

D. The source can deliver maximum power to the load

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8
Q

G5A08 (A)

Why is impedance matching important?

A

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

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9
Q

G5A09 (B)

What unit is used to measure reactance?

A

B. Ohm

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10
Q

G5A10 (B)

What unit is used to measure impedance?

A

B. Ohm

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11
Q

G5A11 (A)

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

A

A. Insert an LC network between the two circuits

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12
Q

G5A12 (B)

What is one reason to use an impedance matching transformer?

A

B. To maximize the transfer of power

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13
Q

G5A13 (D)

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

A

A. A transformer
B. A Pi-network
C. A length of transmission line
D. All of these choices are correct

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14
Q

G5B01 (B)

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

A

B. Approximately 3 dB

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15
Q

G5B02 (C)

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

A

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

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16
Q

G5B03 (B)

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

A

B. 200 watts

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17
Q

G5B04 (A)

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

A

A. 2.4 watts

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18
Q

G5B05 (A)

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

A

A. Approximately 61 milliwatts

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19
Q

G5B06 (B)
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

B. 100 watts

20
Q

G5B07 (C)

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

A

C. The RMS value

21
Q

G5B08 (D) ** QUESTION REMOVED BY QPC February 4, 2015**

22
Q

G5B09 (B)

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

A

B. 12 volts

23
Q

G5B10 (C)

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

A

C. 20.5 percent

24
Q

G5B11 (B)

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

25
Q

G5B12 (B)

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

A

B. 245 volts

26
Q

G5B13 (B)
What is the output PEP of an unmodulated carrier if an average reading wattmeter connected to the transmitter output indicates 1060 watts?

A

B. 1060 watts

27
Q

G5B14 (B)
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

B. 625 watts

28
Q

G5C01 (C)
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

C. Mutual inductance

29
Q

G5C02 (A)

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

A

A. The secondary voltage becomes 4 times the primary voltage

30
Q

G5C03 (B)

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

A

B. A resistor in series

31
Q

G5C04 (C)

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

A

C. 33.3 ohms

32
Q

G5C05 (C)
If three equal value resistors in series produce 450 ohms, what is the value of each resistor?
A. 1500 ohms

A

C. 150 ohms

33
Q

G5C06 (C)
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

C. 26.7 volts

34
Q

G5C07 (A)
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

A. 12.2 to 1

35
Q

G5C08 (D)
What is the equivalent capacitance of two 5.0 nanofarad capacitors and one 750 picofarad capacitor connected in parallel?

A

D. 10.750 nanofarads

36
Q

G5C09 (C)

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

A

C. 33.3 microfarads

37
Q

G5C10 (C)

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

A

C. 3.3 millihenrys

38
Q

G5C11 (C)

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

A

C. 70 millihenrys

39
Q

G5C12 (B)

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

A

B. 14.3 microfarads

40
Q

G5C13 (C)

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

A

C. A capacitor in parallel

41
Q

G5C14 (D)

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

A

D. An inductor in series

42
Q

G5C15 (A)

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

A

A. 5.9 ohms

43
Q

G5C16 (B)
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

B. To accommodate the higher current of the primary

44
Q

G5C17 (C)

What is the value in nanofarads (nF) of a 22,000 pF capacitor?

45
Q

G5C18 (D)

What is the value in microfarads of a 4700 nanofarad (nF) capacitor?

A

D. 4.7 µF

Ham General 2015-2019 (10 decks)

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