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Amateur Radio Question PoolsNew! View the differences between the 2008 Extra question pool and the previous pool. General Class Question PoolPrev 1 2 3 4 5 6 7 8 9 0 NextG5A01 What is impedance? The electric charge stored by a capacitor The inverse of resistance The opposition to the flow of current in an AC circuit The force of repulsion between two similar electric fields G5A02 What is reactance? Opposition to the flow of direct current caused by resistance Opposition to the flow of alternating current caused by capacitance or inductance A property of ideal resistors in AC circuits A large spark produced at switch contacts when an inductor is deenergized G5A03 Which of the following causes opposition to the flow of alternating current in an inductor? Conductance Reluctance Admittance Reactance G5A04 Which of the following causes opposition to the flow of alternating current in a capacitor? Conductance Reluctance Reactance Admittance G5A05 How does a coil react to AC? As the frequency of the applied AC increases, the reactance decreases As the amplitude of the applied AC increases, the reactance increases As the amplitude of the applied AC increases, the reactance decreases As the frequency of the applied AC increases, the reactance increases G5A06 How does a capacitor react to AC? As the frequency of the applied AC increases, the reactance decreases As the frequency of the applied AC increases, the reactance increases As the amplitude of the applied AC increases, the reactance increases 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 internal impedance of the power source? The source delivers minimum power to the load The electrical load is shorted No current can flow through the circuit The source can deliver maximum power to the load G5A08 Why is impedance matching important? So the source can deliver maximum power to the load So the load will draw minimum power from the source To ensure that there is less resistance than reactance in the circuit To ensure that the resistance and reactance in the circuit are equal G5A09 What unit is used to measure reactance? Farad Ohm Ampere Siemens G5A10 What unit is used to measure impedance? Volt Ohm Ampere Watt G5A11 Why should core saturation of a conventional impedance matching transformer be avoided? Harmonics and distortion could result Magnetic flux would increase with frequency RF susceptance would increase Temporary changes of the core permeability could result G5A12 What is one reason to use an impedance matching transformer? To reduce power dissipation in the transmitter To maximize the transfer of power To minimize SWR at the antenna To minimize SWR in the transmission line G5A13 Which of the following devices can be used for impedance matching at radio frequencies? A transformer A Pi-network A length of transmission line All of these choices are correct G5A14 Which of the following describes one method of impedance matching between two AC circuits? Insert an LC network between the two circuits Reduce the power output of the first circuit Increase the power output of the first circuit Insert a circulator between the two circuits G5B01 A two-times increase or decrease in power results in a change of how many dB? 2 dB 3 dB 6 dB 12 dB G5B02 How does the total current relate to the individual currents in each branch of a parallel circuit? It equals the average of each branch current It decreases as more parallel branches are added to the circuit It equals the sum of the currents through each branch 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? 0.5 watts 200 watts 400 watts 3200 watts G5B04 How many watts of electrical power are used by a 12-VDC light bulb that draws 0.2 amperes? 2.4 watts 24 watts 6 watts 60 watts G5B05 How many watts are being dissipated when a current of 7.0 milliamperes flows through 1.25 kilohms? Approximately 61 milliwatts Approximately 39 milliwatts Approximately 11 milliwatts Approximately 9 milliwatts 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? 1.4 watts 100 watts 353.5 watts 400 watts G5B07 Which measurement of an AC signal is equivalent to a DC voltage of the same value? The peak-to-peak value The peak value The RMS value The reciprocal of the RMS value G5B08 What is the peak-to-peak voltage of a sine wave that has an RMS voltage of 120 volts? 84.8 volts 169.7 volts 240.0 volts 339.4 volts G5B09 What is the RMS voltage of sine wave with a value of 17 volts peak? 8.5 volts 12 volts 24 volts 34 volts G5B11 What is the ratio of peak envelope power to average power for an unmodulated carrier? .707 1.00 1.414 2.00 G5B12 What would be the voltage across a 50-ohm dummy load dissipating 1200 watts? 173 volts 245 volts 346 volts 692 volts G5B13 What percentage of power loss would result from a transmission line loss of 1 dB? 10.9 % 12.2 % 20.5 % 25.9 % G5B14 What is the output PEP from a transmitter if an oscilloscope measures 500 volts peak- to-peak across a 50-ohm resistor connected to the transmitter output? 8.75 watts 625 watts 2500 watts 5000 watts G5B15 What is the output PEP of an unmodulated carrier if an average reading wattmeter connected to the transmitter output indicates 1060 watts? 530 watts 1060 watts 1500 watts 2120 watts 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? Capacitive coupling Displacement current coupling Mutual inductance Mutual capacitance G5C02 Where is the source of energy normally connected in a transformer? To the secondary winding To the primary winding To the core To the plates G5C03 What is current in the primary winding of a transformer called if no load is attached to the secondary? Magnetizing current Direct current Excitation current Stabilizing current G5C04 What is the total resistance of three 100-ohm resistors in parallel? .30 ohms .33 ohms 33.3 ohms 300 ohms G5C05 What is the value of each resistor if three equal value resistors in parallel produce 50 ohms of resistance, and the same three resistors in series produce 450 ohms? 1500 ohms 90 ohms 150 ohms 175 ohms G5C06 What is the voltage across a 500-turn secondary winding in a transformer if the 2250- turn primary is connected to 120 VAC? 2370 volts 540 volts 26.7 volts 5.9 volts G5C07 What is the turns ratio of a transformer used to match an audio amplifier having a 600-ohm output impedance to a speaker having a 4-ohm impedance? 12.2 to 1 24.4 to 1 150 to 1 300 to 1 G5C08 What is the equivalent capacitance of two 5000 picofarad capacitors and one 750 picofarad capacitor connected in parallel? 576.9 picofarads 1733 picofarads 3583 picofarads 10750 picofarads G5C09 What is the capacitance of three 100 microfarad capacitors connected in series? .30 microfarads .33 microfarads 33.3 microfarads 300 microfarads G5C10 What is the inductance of three 10 millihenry inductors connected in parallel? .30 Henrys 3.3 Henrys 3.3 millihenrys 30 millihenrys G5C11 What is the inductance of a 20 millihenry inductor in series with a 50 millihenry inductor? .07 millihenrys 14.3 millihenrys 70 millihenrys 1000 millihenrys G5C12 What is the capacitance of a 20 microfarad capacitor in series with a 50 microfarad capacitor? .07 microfarads 14.3 microfarads 70 microfarads 1000 microfarads G5C13 What component should be added to a capacitor in a circuit to increase the circuit capacitance? An inductor in series A resistor in series A capacitor in parallel A capacitor in series G5C14 What component should be added to an inductor in a circuit to increase the circuit inductance? A capacitor in series A resistor in parallel An inductor in parallel An inductor in series G5C15 What is the total resistance of a 10 ohm, a 20 ohm, and a 50 ohm resistor in parallel? 5.9 ohms 0.17 ohms 10000 ohms 80 ohms G5C16 What component should be added to an existing resistor in a circuit to increase circuit resistance? A resistor in parallel A resistor in series A capacitor in series A capacitor in parallel |
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