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General License Ham Radio > Sub Element G5: Electrical Principles > Flashcards

Sub Element G5: Electrical Principles Flashcards

1
Q

What is impedance?

A

The opposition to the flow of current in an AC circuit

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2
Q

What is reactance?

A

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

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3
Q

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

A

Reactance

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4
Q

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

A

Reactance

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5
Q

How does an inductor react to AC?

A

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

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6
Q

How does a capacitor react to AC?

A

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

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7
Q

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 can deliver maximum power to the load

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8
Q

What is one reason to use an impedance matching transformer?

A

To maximize the transfer of power

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9
Q

What unit is used to measure reactance?

A

Ohm

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10
Q

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

A

A transformer
A Pi-network
A length of transmission line
All these choices are correct

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11
Q

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

A

Insert an LC network between the two circuits

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12
Q

What dB change represents a factor of two increase or decrease in power?

A

Approximately 3 dB

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13
Q

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

A

It equals the sum of the currents through each branch

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14
Q

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

A

200 watts

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15
Q

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

A

2.4 watts

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16
Q

How many watts are dissipated when a current of 7.0 milliamperes flows through a 1250 ohm resistance?

A

Approximately 61 milliwatts

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17
Q

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

100 watts

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18
Q

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

A

The RMS value

19
Q

What is the peak-to-peak voltage of a sine wave with an RMS voltage of 120.0 volts?

A

339.4 volts

20
Q

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

A

12 volts

21
Q

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

A

20.6 percent

22
Q

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

A

1.00

23
Q

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

A

245 volts

24
Q

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

A

1060 watts

25
Q

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

625 watts

26
Q

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

Mutual inductance

27
Q

What happens if a signal is applied to the secondary winding of a 4:1 voltage step- down transformer instead of the primary winding??

A

The output voltage is multiplied by 4

28
Q

Which of the following components increases the total resistance of a resistor?

A

A series resistor

29
Q

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

A

33.3 ohms

30
Q

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

A

150 ohms

31
Q

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

26.7 volts

32
Q

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

33
Q

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

A

10.750 nanofarads

34
Q

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

A

33.3 microfarads

35
Q

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

A

3.3 millihenries

36
Q

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

A

70 millihenries

37
Q

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

A

14.3 microfarads

38
Q

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

A

A capacitor in parallel

39
Q

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

A

An inductor in series

40
Q

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

A

5.9 ohms

41
Q

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 accommodate the higher current of the primary

42
Q

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

A

22

43
Q

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

A

4.7

General License Ham Radio (10 decks)

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