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An ac series circuit has 12 ohms resistance, 15 ohms inductive reactance and 10 ohms capacitive reactance. If an effective emf of 120 V is applied to the circuit, then what is the effective (rms) current value?
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1. 3.3 A
2. 4.0 A
3. 9.2 A
4. 36.0 A
The primary winding of an electric train transformer has 400 turns and the secondary has 50. If the input voltage is 120 V(rms), what is the output voltage?
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1. 480.0 V
2. 60.0 V
3. 15.0 V
4. 10.0 V
An ac series circuit has 12 ohms resistance, 15 ohms inductive reactance and 10 ohms capacitive reactance. If an effective (rms) emf of 120 V is applied, what is the power output?
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1. 1200 W
2. 1108 W
3. 1022 W
4. 598 W
A transformer consists of a 500 turn primary coil and a 2000 secondary coil. If the current in the secondary is 3.0 amps, what is the primary current?
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1. 0.75 A
2. 1.33 A
3. 12.0 A
4. 48.0 A
In an ac series circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?
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1. zero
2. 45°
3. 90°
4. 180°
In an ac series circuit, the voltage in the inductor differs in phase with the voltage in the capacitor by what angle?
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1. zero
2. 45°
3. 90°
4. 180°
The capacitive reactance in an ac series circuit will change by what factor when the frequency is tripled?
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1. 1/3
2. 1/9
3. 3
4. 9
An ac series circuit with a peak current of 20 A will have what effective (rms) current?
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1. 28.2 A
2. 7.1 A
3. 14.1 A
4. 20.0 A
In the inductor of a 60 cycle ac series circuit, the peak voltage precedes the peak current in each cycle by what time intervals?
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1. 2.1 x 10-3 s
2. 4.2 x 10-3 s
3. 8.3 x 10-3 s
4. 16.7 x 10-3 s
An ac series circuit with 12 ohms resistance, 15 ohms inductive reactance and 10 ohms capacitive reactance has how many ohms of impedance?
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1. 37.0 W
2. 27.7 W
3. 21.9 W
4. 13.0 W
An ac series circuit with 12 ohms resistance, 15 ohms inductive reactance and 10 ohms capacitive reactance has what phase angle?
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1. 22.6°
2. 18.4°
3. 87.0°
4. 67.4°
Peak values for a neodymium-glass laser are 600 joules for 1 nanosecond. If the cross-section of the laser beam is 1 cm2, what are the maximum values of E and B? ( µ0 = 4π x 10-7 T-m/A)
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1. 4 x 107 V/m, 0.3 T
2. 3 x 108 V/m, 1.0 T
3. 2 x 109 V/m, 7.0 T
4. 5 x 106 V/m, 0.1 T
A solar cell has a light-gathering area of 10 cm2 and produces 0.2 A at 0.8 V (DC) when illuminated with sunlight of intensity 1000 W/m2. What is the efficiency of the solar cell?
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1. 16%
2. 7%
3. 23%
4. 4%
If the radiant energy from the sun comes in as a plane EM wave of intensity 1340 W/m2, calculate the peak values of E and B. ( µ0 = 4π x 10-7 T-m/A)
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1. 300 V/m, 10-4 T
2. 1000 V/m, 3.3 x 10-6 T
3. 225 V/m, 1.6 x 10-3 T
4. 111 V/m, 3.0 x 10-5 T
Find the frequency of x-rays of wavelength 10-10 m.
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1. 3 x 1018 Hz
2. 3 x 1010 MHz
3. 6 x 109 Hz
4. 3 x 108 HZ
What is the maximum value of the electric field E at 1 meter from a 100-watt lightbulb radiating in all directions? (µ0 = 4π x 10-7 T-m/A)
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1. 1000 V/m
2. 2000 V/m
3. 4000 V/m
4. 6000 V/m
What is the wavelength of 100 MHz television EM-waves?
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1. 0.3 cm
2. 3 m
3. 9 km
4. 10 m
Determine the amount of energy carried in 1 meter of a 3.5-milliwatt He-Ne laser beam if the cross-sectional area of the beam is 5 x 10-6 m2.
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1. 0.014 J
2. 0.4 J
3. 0.175 mJ
4. 1 J
The Earth is 1.49 x 1011 meters from the sun. If the solar radiation at the top of the Earth's atmosphere is 1340 W/m2, what is the total power output of the sun?
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1. 7 x 1027 W
2. 2 x 1030 W
3. 6.6 x 1026 W
4. 3.7 x 1026 W
Maxwell guessed that visible light was an electromagnetic wave because of its?
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1. frequency.
2. wavelength.
3. speed.
4. energy.
As an electromagnetic wave travels through free space, its speed can be increased by?
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1. increasing its frequency.
2. increasing its energy only.
3. increasing both its energy and momentum.
4. none of the choices will increase its speed.
An object that is giving off only infrared electromagnetic waves is giving off heat through?
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1. convection.
2. conduction.
3. radiation.
4. visible light.
A camera that takes infrared photographs in the dark takes these pictures by?
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1. using film sensitive to invisible radiation.
2. amplifying the electromagnetic radiation.
3. illuminating the object with infrared light.
4. using infrared filters.
The electromagnetic radiation that causes tanning?
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1. can produce cancer.
2. rarely passes through glass windows.
3. is absorbed by ozone.
4. all of the choices
Maxwell developed his theory of electromagnetism by combining previous discoveries. He added his own original hypothesis that?
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1. electrical charges produce electrical fields.
2. moving electrical charges produce magnetic fields.
3. changing electrical fields produce magnetic fields.
4. changing magnetic fields produce electrical fields.
Of the various types of electromagnetic radiation, which is the most penetrating through all forms of matter?
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1. infrared
2. gamma
3. visible light
4. ultraviolet
What value of inductance should be used in a series circuit with a capacitor of 1.8 x 10-3 microfarads when designed to radiate a wavelength of 35 m? (c = 3 x 108 m/s)
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1. 3.8 mH
2. 2.6 x 10-2 mH
3. 3.8 x 10-3 mH
4. 1.9 x 10-4 mH
Temperature variation of different parts of a person's body can be detected by analyzing the emission pattern of which type of electromagnetic radiation?
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1. microwave
2. infrared
3. ultraviolet
4. X-rays
Microwave ovens emit a frequency intended to be in resonance with which of the following?
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1. frequency of water molecule
2. size of oven compartment
3. frequency of metal lining of oven
4. frequency of food molecules
The phenomenon used by police radar is which of the following?
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1. absorption
2. resonance
3. reflection
4. refraction
An ultraviolet light has a wavelength of 300 nm and speed of 2.1 x 108 m/s through a transparent medium. What is the frequency of this wave in the medium? (1 nm = 10-9 m and c = 3 x 108 m/s)
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1. 6.3 x 102 Hz
2. 9 x 102 Hz
3. 7 x 1014 Hz
4. 10 x 1014 Hz
How is the direction of propagation of an electromagnetic wave oriented relative to the associated E and B fields?
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1. parallel to both E and B
2. perpendicular to both E and B
3. parallel to E, perpendicular to B
4. parallel to B, perpendicular to E
Microwave radiation is useful in which of the following?
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1. sending phone messages
2. cooking food
3. aircraft navigation
4. All of the choices are valid choices
The human eye is sensitive to light with wavelength down to 390 nm. What is the frequency of radiation at this wavelength? (1 nm = 10-9 m and c = 3 x 108 m/s)
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1. 1.8 x 108 Hz
2. 8.5 x 108 Hz
3. 1.1 x 1011 Hz
4. 7.7 x 1014 Hz
An AM radio turning circuit has a coil with an inductance of 6.0 mH and a capacitor set at 7.5 x 10-6 microfarads. What frequency will it detect?
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1. 551 kHz
2. 750 kHz
3. 1061 kHz
4. 1520 kHz
An FM radio tuning circuit has a coil with an inductance of 0.003 mH. What is the value of the capacitance if the set is tuned to 98 MHz?
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1. 1.76 x 10-6 microfarads
2. 12.3 x 10-6 microfarads
3. 0.98 x 10-6 microfarads
4. 0.88 x 10-6 microfarads
A radio wave transmits 1.2 W/m2 average power per unit area. What is the peak value of the associated magnetic field? (magnetic permeability = 4π x 10-7 T x m/A and c = 3 x 108 m/s)
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1. 1.0 x 10-7 T
2. 8.4 x 10-3 T
3. 1.2 T
4. 30 T
A radar pulse sent out to an airplane at a distance of 20 km will return as an echo to the source in what time interval? (c = 3 x 108 m/s)
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1. 33.3 x 10-6 s
2. 66.7 x 10-6 s
3. 133 x 10-6 s
4. 0.033 x 10-6 s
An electromagnetic wave with a peak magnetic field component of 1.5 x 10-7 Wb/m2 carries what average power per unit area? (magnetic permeability = 4π x 10-7 T x m/A, electric permittivity = 8.85 x 10-12 C2 /N-m2 and c = 3 x 108 m/s)
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1. 12.4 T
2. 2.70 T
3. 3.00 T
4. 1.30 T
A radio wave signal which transmits at a frequency of 7.2 MHz has what wavelength? (c = 3 x 108 m/s)
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1. 41.7 m
2. 4.2 m
3. 28.8 m
4. 2.4 x 10-2 m
An electromagnetic wave with a peak magnetic field component of 1.5 x 10-7 Wb/m2 has an associated peak electric field component of what value? (magnetic permeability = 4π x 10-7 T x m/A,electric permittivity = 8.85 x 10-12 C2 /N-m2 and c = 3 x 108 m/s)
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1. 0.50 x 10-15 N/C
2. 2.00 x 10-5 N/C
3. 2.20 x 104 N/C
4. 45 N/C
Which one of the following scientists first built and operated devices that could emit and detect man-made electromagnetic radiation?
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1. Hertz
2. Ampere
3. Maxwell
4. Lenz
Which condition of motion must be met with regard to a charged particle if it is in the process of emitting electromagnetic radiation?
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1. moves at constant velocity
2. accelerates
3. moves at the speed of light
4. moves parallel to a uniform magnetic field
The electric field, E, in an electromagnetic wave is oriented in what direction with respect to its associated magnetic field, B?
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1. E parallel to B
2. E anti-parallel to B
3. E perpendicular to B
4. E at a 45° angle to B
Which one of the following scientists made the theoretical prediction that electromagnetic waves travel through a vacuum at the speed of light?
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1. Hertz
2. Faraday
3. Maxwell
4. Lenz
A radar pulse returns 3.0 x 10-4 seconds after it is sent out when reflected from an object. What is the distance between the radar and object? (c = 3 x 108 m/s)
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1. 9.0 x 104 m
2. 4.5 x 104 m
3. 6.0 x 104 m
4. 1.0 x 104 m
In order to keep its food hot, a restaurant will place it under which type of lamp?
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1. infrared
2. visible light
3. ultraviolet
4. X-ray
An electromagnetic wave with a peak electric field component of 1.2 x 102 N/C has what associated peak magnetic field value? (electrical permittivity = 8.85 x 10-12 C2 /N-m2 magnetic permeability = 4π x 10-7 T x m/A and c = 3 x 108 m/s)
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1. 4.0 x 10-7 T
2. 3.6 x 1010 T
3. 2.5 x 106 T
4. 2.8 x 10-11 T
Glass panes are opaque to a certain type of radiation which passes through quartz. What type of radiation is it?
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1. microwave
2. gamma
3. X-ray
4. ultraviolet
A 200 W resistor is connected in series with a 10 µ F capacitor and a 60 Hz 120 V rms line voltage. If electrical energy costs 5¢ per kWh. How much does it cost to leave this circuit connected for 24 hours?
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1. 62¢
2. 31¢
3. 5.2¢
4. 0.6¢
An electromagnetic wave is made up of which of the following oscillating quantities?
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1. electrons only
2. electric fields only
3. magnetic fields only
4. electric and magnetic fields
A 50 W resistor, a 0.1 H inductor, and a 10 µ F capacitor are connected in series to a 60 Hz source. The rms current in the circuit is 3 A. Find the rms voltage across the resistor, the inductor, and the capacitor.
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1. 150 V-rms, 113 V-rms, 795 V-rms
2. .06 V-rms, 80 V-rms, 562 V-rms
3. 150 V-rms, 113 V-rms, 562 V-rms
4. 60 V-rms, 80 V-rms, 795 V-rms
In order of increasing frequency, which of the following is correct?
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1. radio, visible, infrared and X-ray
2. infrared, visible, X-ray and gamma
3. visible, infrared, ultraviolet and X-ray
4. infrared, ultraviolet, visible and gamma
Find the resonant frequency for a series RLC circuit where R = 10W, C = 5 µF, and L = 2 mH.
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1. 998 Hz
2. 1.592 kHz
3. 2.45 kHz
4. 11.3 kHz
What is the average power dissipation in an RLC series circuit R = 100 W, L = 0.1 H, C = 10 µF driven at resonance by a 100 V-rms source?
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1. 100 W
2. 500 W
3. 1000 W
4. 2 W
What is the average power dissipation in a series RC circuit if R = 5 kW, C = 2 µF, and V = 170 cos 300 t?
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1. 0.93 W
2. 2.74 W
3. 28.2 W
4. 157 W
A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission-line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have?
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1. 6
2. 70
3. 920
4. 9200
A series RLC circuit in a radio is in resonance with AM 770 kHz. If the radio station is changed to AM 1540 kHz, by what factor must the capacitance be multiplied to again achieve resonance?
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1. 4
2. 2
3. 1/2
4. 1/4
An ac power generator produces 50 A (rms) at 3600 V. The voltage is stepped up to 100,000 V by an ideal transformer and the energy transmitted through a long distance power line with a total resistance of 100 ohms. What is the rms current in the long distance line?
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1. 1.0 A
2. 1.8 A
3. 24 A
4. 1000 A
An ac power generator produces 25 A (rms) at 3600 V. The energy is transmitted through a long distance power line which has a total resistance of 100 ohms. What percentage of the power delivered by the generator is dissipated as heat in the long distance line if a step-up transformer is not used?
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1. 0.09%
2. 1.8%
3. 32%
4. 69%
In an ac circuit, the ratio of average current to maximum current is?
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1. zero
2. 0.5
3. 0.707
4. 1.0
The current in an inductor connected to an ac voltage source lags the voltage. This lag is caused by?
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1. the back emf in the coil
2. the voltage across the coil
3. the time required for electrical signals to travel through all the coils of an inductance
4. the resistance of the coil
A resistor, inductor and capacitor are connected in series, each with effective (rms) voltage of 65 V, 140 V and 80 V, respectively. If the resistor is rated at 24 ohms, what is the average power dissipated in the circuit?
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1. 88 watts
2. 132 watts
3. 238 watts
4. 323 watts
An ac series circuit contains a resistor of 20 ohms, an inductor of 30 mH and a variable capacitor. If the frequency of the applied voltage is 500 Hz, to what setting should the capacitor be set if resonance is achieved?
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1. 0.8 microfarads
2. 1.6 microfarads
3. 2.4 microfarads
4. 3.4 microfarads
A resistor and capacitor are connected in series with an applied ac voltage source. Voltmeter readings across the resistor and capacitor separately, give values of 50 V and 75 V (rms), respectively. What is the effective (rms) voltage of the source?
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1. 25 V
2. 63 V
3. 90 V
4. 125 V
A resistor, inductor and capacitor are connected in series, each with effective (rms) voltage of 65 V, 140 V and 80 V, respectively. What is the value of the effective voltage of the applied source in the circuit?
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1. 48 V
2. 88 V
3. 95 V
4. 285 V
A resistor, inductor and capacitor are connected in series, each with effective (rms) voltage of 65 V, 140 V and 80 V, respectively. What is the phase angle in this circuit?
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1. 22°
2. 28°
3. 37°
4. 43°
An ac series circuit contains a resistor of 20 ohms, a capacitor of 0.75 microfarads and an inductor of 120 mH. If an effective (rms) voltage of 120 V is applied, what is the effective (rms) current when the circuit is in resonance?
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1. 4.3 A
2. 6.0 A
3. 10.3 A
4. 17.1 A
An ac voltage source, with a peak output of 200 V, is connected to a 50 ohm resistor. What is the effective, (or rms), current in the circuit?
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1. 2.82 A
2. 4.0 A
3. 5.64 A
4. 2.0 A
An ac voltage source, with a peak output of 200 V, is connected to a 50 ohm resistor. What is the rate of heating power in the resistor?
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1. 200 W
2. 400 W
3. 566 W
4. 800 W
The power factor in an ac series circuit is equal to which of the following ratios?
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1. resistance to inductive reactance
2. capacitive reactance to inductive reactance
3. inductive reactance to capacitive reactance
4. resistance to impedance
In an ac series circuit the capacitive reactance is 200 ohms and frequency is 100 Hz. What is the capacitance?
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1. 3.2 microfarads
2. 6.28 microfarads
3. 8.0 microfarads
4. 50.0 microfarads
In an ac series circuit the inductive reactance is 50 ohms and the frequency is 100 Hz. What is the inductance in the circuit?
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1. 80 mH
2. 240 mH
3. 500 mH
4. 740 mH
An ac series circuit contains a resistor of 20 ohms, a capacitor of 0.75 microfarads and an inductor of 120 mH. What frequency should be used to create a resonance condition in the circuit?
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1. 159 Hz
2. 318 Hz
3. 637 Hz
4. 530 Hz
Consider an ac series circuit containing a coil, capacitor and resistance. Tripling the frequency will change the inductive reactance by what factor?
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1. 1/3
2. 1.0
3. 1.73
4. 3.0
Consider an ac series circuit containing a coil, capacitor and resistance. Tripling the frequency will change the capacitive reactance by what factor?
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1. 1/3
2. 1.0
3. 1.73
4. 3.0
Consider an ac series circuit containing a coil, capacitor and resistance. Tripling the frequency will change the circuit's impedance by what factor?
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1. 1/3
2. 1.0
3. 3.0
4. Information is insufficient to determine answer
The rate of heat dissipation in an ac circuit with resistance, R, and effective current, I, is given by which of the following?
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1. 0.5 x I2 R
2. I2 R
3. 2.0 x I2 R
4. 4.0 x I2 R
Resonance occurs in an ac series circuit when which of the following conditions is met?
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1. resistance equals capacitive reactance
2. resistance equals inductive reactance
3. capacitive reactance equals inductive reactance
4. capacitive reactance equals zero
The power dissipated in an ac series circuit increases as the phase angle approaches what value?
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1. zero
2. 45°
3. 90°
4. 180°
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