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Amateur Radio Question PoolsNew! View the differences between the 2008 Extra question pool and the previous pool. Amateur Extra (Eff. July 2008) Question PoolPrev 1 2 3 4 5 6 7 8 9 0 NextE5A01 What can cause the voltage across reactances in series to be larger than the voltage applied to them? Resonance Capacitance Conductance Resistance E5A02 What is resonance in an electrical circuit? The highest frequency that will pass current The lowest frequency that will pass current The frequency at which the capacitive reactance equals the inductive reactance The frequency at which the reactive impedance equals the resistive impedance E5A03 What is the magnitude of the impedance of a series R-L-C circuit at resonance? High, as compared to the circuit resistance Approximately equal to capacitive reactance Approximately equal to inductive reactance Approximately equal to circuit resistance E5A04 What is the magnitude of the impedance of a circuit with a resistor, an inductor and a capacitor all in parallel, at resonance? Approximately equal to circuit resistance Approximately equal to inductive reactance Low, as compared to the circuit resistance Approximately equal to capacitive reactance E5A05 What is the magnitude of the current at the input of a series R-L-C circuit as the frequency goes through resonance? Minimum Maximum R/L L/R E5A06 What is the magnitude of the circulating current within the components of a parallel L-C circuit at resonance? ((Was E5A08) It is at a minimum It is at a maximum It equals 1 divided by the quantity [ 2 multiplied by Pi, multiplied by the square root of ( inductance "L" multiplied by capacitance "C" ) ] It equals 2 multiplied by Pi, multiplied by frequency "F", multiplied by inductance "L" E5A07 What is the magnitude of the current at the input of a parallel R-L-C circuit at resonance? Minimum Maximum R/L L/R E5A08 What is the phase relationship between the current through and the voltage across a series resonant circuit? The voltage leads the current by 90 degrees The current leads the voltage by 90 degrees The voltage and current are in phase The voltage and current are 180 degrees out of phase E5A09 What is the phase relationship between the current through and the voltage across a parallel resonant circuit? The voltage leads the current by 90 degrees The current leads the voltage by 90 degrees The voltage and current are in phase The voltage and current are 180 degrees out of phase E5A10 What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 1.8 MHz and a Q of 95? 18.9 kHz 1.89 kHz 94.5 kHz 9.45 kHz E5A11 What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 7.1 MHz and a Q of 150? 157.8 Hz 315.6 Hz 47.3 kHz 23.67 kHz E5A12 What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 3.7 MHz and a Q of 118? 436.6 kHz 218.3 kHz 31.4 kHz 15.7 kHz E5A13 What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 14.25 MHz and a Q of 187? 38.1 kHz 76.2 kHz 1.332 kHz 2.665 kHz E5A14 What is the resonant frequency of a series RLC circuit if R is 22 ohms, L is 50 microhenrys and C is 40 picofarads? 44.72 MHz 22.36 MHz 3.56 MHz 1.78 MHz E5A15 What is the resonant frequency of a series RLC circuit if R is 56 ohms, L is 40 microhenrys and C is 200 picofarads? 3.76 MHz 1.78 MHz 11.18 MHz 22.36 MHz E5A16 What is the resonant frequency of a parallel RLC circuit if R is 33 ohms, L is 50 microhenrys and C is 10 picofarads? 23.5 MHz 23.5 kHz 7.12 kHz 7.12 MHz E5A17 What is the resonant frequency of a parallel RLC circuit if R is 47 ohms, L is 25 microhenrys and C is 10 picofarads? 10.1 MHz 63.2 MHz 10.1 kHz 63.2 kHz E5B01 What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the supply voltage? An exponential rate of one One time constant One exponential period A time factor of one E5B02 What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial value of stored charge? One discharge period An exponential discharge rate of one A discharge factor of one One time constant E5B03 The capacitor in an RC circuit is discharged to what percentage of the starting voltage after two time constants? 86.5% 63.2% 36.8% 13.5% E5B04 What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in parallel? 55 seconds 110 seconds 440 seconds 220 seconds E5B05 How long does it take for an initial charge of 20 V DC to decrease to 7.36 V DC in a 0.01-microfarad capacitor when a 2-megohm resistor is connected across it? 0.02 seconds 0.04 seconds 20 seconds 40 seconds E5B06 How long does it take for an initial charge of 800 V DC to decrease to 294 V DC in a 450-microfarad capacitor when a 1-megohm resistor is connected across it? 4.50 seconds 9 seconds 450 seconds 900 seconds E5B07 What is the phase angle between the voltage across and the current through a series R-L-C circuit if XC is 500 ohms, R is 1 kilohm, and XL is 250 ohms? 68.2 degrees with the voltage leading the current 14.0 degrees with the voltage leading the current 14.0 degrees with the voltage lagging the current 68.2 degrees with the voltage lagging the current E5B08 What is the phase angle between the voltage across and the current through a series R-L-C circuit if XC is 100 ohms, R is 100 ohms, and XL is 75 ohms? 14 degrees with the voltage lagging the current 14 degrees with the voltage leading the current 76 degrees with the voltage leading the current 76 degrees with the voltage lagging the current E5B09 What is the relationship between the current through and the voltage across a capacitor? (was E5D06) Voltage and current are in phase Voltage and current are 180 degrees out of phase Voltage leads current by 90 degrees Current leads voltage by 90 degrees E5B10 What is the relationship between the current through an inductor and the voltage across an inductor? (was E5D07) Voltage leads current by 90 degrees Current leads voltage by 90 degrees Voltage and current are 180 degrees out of phase Voltage and current are in phase E5B11 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 ohms, R is 100 ohms, and XL is 50 ohms? (was E5D08) 14 degrees with the voltage lagging the current 14 degrees with the voltage leading the current 76 degrees with the voltage lagging the current 76 degrees with the voltage leading the current E5B12 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 75 ohms, R is 100 ohms, and XL is 50 ohms? (was E5D10) 76 degrees with the voltage lagging the current 14 degrees with the voltage leading the current 14 degrees with the voltage lagging the current 76 degrees with the voltage leading the current E5B13 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 250 ohms, R is 1 kilohm, and XL is 500 ohms? (was E5D11) 81.47 degrees with the voltage lagging the current 81.47 degrees with the voltage leading the current 14.04 degrees with the voltage lagging the current 14.04 degrees with the voltage leading the current E5C01 In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance inductor in series with a 100-ohm resistor? 121 ohms at an angle of 35 degrees 141 ohms at an angle of 45 degrees 161 ohms at an angle of 55 degrees 181 ohms at an angle of 65 degrees E5C02 In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance inductor, a 100-ohm-reactance capacitor, and a 100-ohm resistor all connected in series? 100 ohms at an angle of 90 degrees 10 ohms at an angle of 0 degrees 10 ohms at an angle of 90 degrees 100 ohms at an angle of 0 degrees E5C03 In polar coordinates, what is the impedance of a network consisting of a 300-ohm-reactance capacitor, a 600-ohm-reactance inductor, and a 400-ohm resistor, all connected in series? 500 ohms at an angle of 37 degrees 900 ohms at an angle of 53 degrees 400 ohms at an angle of 0 degrees 1300 ohms at an angle of 180 degrees E5C04 In polar coordinates, what is the impedance of a network consisting of a 400-ohm-reactance capacitor in series with a 300-ohm resistor? 240 ohms at an angle of 36.9 degrees 240 ohms at an angle of -36.9 degrees 500 ohms at an angle of 53.1 degrees 500 ohms at an angle of -53.1 degrees E5C05 In polar coordinates, what is the impedance of a network consisting of a 400-ohm-reactance inductor in parallel with a 300-ohm resistor? 240 ohms at an angle of 36.9 degrees 240 ohms at an angle of -36.9 degrees 500 ohms at an angle of 53.1 degrees 500 ohms at an angle of -53.1 degrees E5C06 In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance capacitor in series with a 100-ohm resistor? 121 ohms at an angle of -25 degrees 191 ohms at an angle of -85 degrees 161 ohms at an angle of -65 degrees 141 ohms at an angle of -45 degrees E5C07 In polar coordinates, what is the impedance of a network comprised of a 100-ohm-reactance capacitor in parallel with a 100-ohm resistor? 31 ohms at an angle of -15 degrees 51 ohms at an angle of -25 degrees 71 ohms at an angle of -45 degrees 91 ohms at an angle of -65 degrees E5C08 In polar coordinates, what is the impedance of a network comprised of a 300-ohm-reactance inductor in series with a 400-ohm resistor? 400 ohms at an angle of 27 degrees 500 ohms at an angle of 37 degrees 500 ohms at an angle of 47 degrees 700 ohms at an angle of 57 degrees E5C09 When using rectangular coordinates to graph the impedance of a circuit, what does the horizontal axis represent? The voltage or current associated with the resistive component The voltage or current associated with the reactive component The sum of the reactive and resistive components The difference between the resistive and reactive components E5C10 When using rectangular coordinates to graph the impedance of a circuit, what does the vertical axis represent? The voltage or current associated with the resistive component The voltage or current associated with the reactive component The sum of the reactive and resistive components The difference between the resistive and reactive components E5C11 What do the two numbers represent that are used to define a point on a graph using rectangular coordinates? The magnitude and phase of the point The sine and cosine values The coordinate values along the horizontal and vertical axes The tangent and cotangent values E5C12 If you plot the impedance of a circuit using the rectangular coordinate system and find the impedance point falls on the right side of the graph on the horizontal line, what do you know about the circuit? It has to be a direct current circuit It contains resistance and capacitive reactance It contains resistance and inductive reactance It is equivalent to a pure resistance E5C13 What coordinate system is often used to display the resistive, inductive, and/or capacitive reactance components of an impedance? Maidenhead grid Faraday grid Elliptical coordinates Rectangular coordinates E5C14 What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance? Maidenhead grid Faraday grid Elliptical coordinates Rectangular coordinates E5C15 In polar coordinates, what is the impedance of a circuit of 100 -j100 ohms impedance? 141 ohms at an angle of -45 degrees 100 ohms at an angle of 45 degrees 100 ohms at an angle of -45 degrees 141 ohms at an angle of 45 degrees E5C16 In polar coordinates, what is the impedance of a circuit that has an admittance of 7.09 millisiemens at 45 degrees? 5.03 x 10 –E05 ohms at an angle of 45 degrees 141 ohms at an angle of -45 degrees 19,900 ohms at an angle of -45 degrees 141 ohms at an angle of 45 degrees E5C17 In rectangular coordinates, what is the impedance of a circuit that has an admittance of 5 millisiemens at -30 degrees? 173 - j100 ohms 200 + j100 ohms 173 + j100 ohms 200 - j100 ohms E5C18 In polar coordinates, what is the impedance of a series circuit consisting of a resistance of 4 ohms, an inductive reactance of 4 ohms, and a capacitive reactance of 1 ohm? 6.4 ohms at an angle of 53 degrees 5 ohms at an angle of 37 degrees 5 ohms at an angle of 45 degrees 10 ohms at an angle of -51 degrees E5C19 Which point on Figure E5-2 best represents that impedance of a series circuit consisting of a 400 ohm resistor and a 38 picofarad capacitor at 14 MHz? Point 2 Point 4 Point 5 Point 6 E5C20 Which point in Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and an 18 microhenry inductor at 3.505 MHz? Point 1 Point 3 Point 7 Point 8 E5C21 Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and a 19 picofarad capacitor at 21.200 MHz? Point 1 Point 3 Point 7 Point 8 E5C22 In rectangular coordinates, what is the impedance of a network comprised of a 10-microhenry inductor in series with a 40-ohm resistor at 500 MHz? 40 + j31,400 40 - j31,400 31,400 + j40 31,400 - j40 E5C23 Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300-ohm resistor, a 0.64-microhenry inductor and an 85-picofarad capacitor at 24.900 MHz? Point 1 Point 3 Point 5 Point 8 E5D01 What is the result of skin effect? As frequency increases, RF current flows in a thinner layer of the conductor, closer to the surface As frequency decreases, RF current flows in a thinner layer of the conductor, closer to the surface Thermal effects on the surface of the conductor increase the impedance Thermal effects on the surface of the conductor decrease the impedance E5D02 Why is the resistance of a conductor different for RF currents than for direct currents? Because the insulation conducts current at high frequencies Because of the Heisenburg Effect Because of skin effect Because conductors are non-linear devices E5D03 What device is used to store electrical energy in an electrostatic field? A battery A transformer A capacitor An inductor E5D04 What unit measures electrical energy stored in an electrostatic field? Coulomb Joule Watt Volt E5D05 What is a magnetic field? Current through the space around a permanent magnet The space through which a magnetic force acts The space between the plates of a charged capacitor, through which a magnetic force acts The force that drives current through a resistor E5D06 In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow? In the same direction as the current In a direction opposite to the current In all directions; omnidirectional In a direction determined by the left-hand rule E5D07 What determines the strength of a magnetic field around a conductor? The resistance divided by the current The ratio of the current to the resistance The diameter of the conductor The amount of current E5D08 What is the term for energy that is stored in an electromagnetic or electrostatic field? Amperes-joules Potential energy Joules-coulombs Kinetic energy E5D09 What is the term for an out-of-phase, nonproductive power associated with inductors and capacitors? Effective power True power Peak envelope power Reactive power E5D10 In a circuit that has both inductors and capacitors, what happens to reactive power? It is dissipated as heat in the circuit It is repeatedly exchanged between the associated magnetic and electric fields, but is not dissipated It is dissipated as kinetic energy in the circuit It is dissipated in the formation of inductive and capacitive fields E5D11 How can the true power be determined in an AC circuit where the voltage and current are out of phase? By multiplying the apparent power times the power factor By dividing the reactive power by the power factor By dividing the apparent power by the power factor By multiplying the reactive power times the power factor E5D12 What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current? 1.414 0.866 0.5 1.73 E5D13 How many watts are consumed in a circuit having a power factor of 0.2 if the input is 100-V AC at 4 amperes? 400 watts 80 watts 2000 watts 50 watts E5D14 How much power is consumed in a circuit consisting of a 100 ohm resistor in series with a 100 ohm inductive reactance drawing 1 ampere? 70.7 Watts 100 Watts 141.4 Watts 200 Watts E5D15 What is reactive power? Wattless, nonproductive power Power consumed in wire resistance in an inductor Power lost because of capacitor leakage Power consumed in circuit Q E5D16 What is the power factor of an RL circuit having a 45 degree phase angle between the voltage and the current? 0.866 1.0 0.5 0.707 E5D17 What is the power factor of an RL circuit having a 30 degree phase angle between the voltage and the current? (was E5H14) 1.73 0.5 0.866 0.577 E5D18 How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200V AC at 5 amperes? 200 watts 1000 watts 1600 watts 600 watts E5D19 How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500 watts? 704 W 355 W 252 W 1.42 mW |
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