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?

1
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?

1. 3.3 A
2. 4.0 A
3. 9.2 A
4. 36.0 A

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2
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?

1. 480.0 V
2. 60.0 V
3. 15.0 V
4. 10.0 V

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3
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?

1. 1200 W
2. 1108 W
3. 1022 W
4. 598 W

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4
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?

1. 0.75 A
2. 1.33 A
3. 12.0 A
4. 48.0 A

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5
In an ac series circuit, the current in a pure
resistor differs in phase with the applied
voltage by what angle?

1. zero
2. 45
3. 90
4. 180

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6
In an ac series circuit, the voltage in the
inductor differs in phase with the voltage in the
capacitor by what angle?

1. zero
2. 45
3. 90
4. 180

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7
The capacitive reactance in an ac series circuit
will change by what factor when the frequency is
tripled?

1. 1/3
2. 1/9
3. 3
4. 9

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8
An ac series circuit with a peak current of 20 A
will have what effective (rms) current?

1. 28.2 A
2. 7.1 A
3. 14.1 A
4. 20.0 A

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9
In the inductor of a 60 cycle ac series circuit,
the peak voltage precedes the peak current in
each cycle by what time intervals?

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

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10
An ac series circuit with 12 ohms resistance, 15
ohms inductive reactance and 10 ohms capacitive
reactance has how many ohms of impedance?

1. 37.0 W
2. 27.7 W
3. 21.9 W
4. 13.0 W

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11
An ac series circuit with 12 ohms resistance, 15
ohms inductive reactance and 10 ohms capacitive
reactance has what phase angle?

1. 22.6
2. 18.4
3. 87.0
4. 67.4

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12
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 4p x 10-7 T-m/A)

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

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13
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?

1. 16
2. 7
3. 23
4. 4

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14
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 4p x 10-7
T-m/A)

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

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15
Find the frequency of x-rays of wavelength 10-10
m.

1. 3 x 1018 Hz
2. 3 x 1010 MHz
3. 6 x 109 Hz
4. 3 x 108 HZ

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16
What is the maximum value of the electric field E
at 1 meter from a 100-watt lightbulb radiating in
all directions? (µ0 4p x 10-7 T-m/A)

1. 1000 V/m
2. 2000 V/m
3. 4000 V/m
4. 6000 V/m

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17
What is the wavelength of 100 MHz television
EM-waves?

1. 0.3 cm
2. 3 m
3. 9 km
4. 10 m

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18
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.

1. 0.014 J
2. 0.4 J
3. 0.175 mJ
4. 1 J

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19
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?

1. 7 x 1027 W
2. 2 x 1030 W
3. 6.6 x 1026 W
4. 3.7 x 1026 W

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20
Maxwell guessed that visible light was an
electromagnetic wave because of its?

1. frequency.
2. wavelength.
3. speed.
4. energy.

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21
As an electromagnetic wave travels through free
space, its speed can be increased by?

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.

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22
An object that is giving off only infrared
electromagnetic waves is giving off heat through?

1. convection.
2. conduction.
3. radiation.
4. visible light.

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23
A camera that takes infrared photographs in the
dark takes these pictures by?

1. using film sensitive to invisible radiation.
2. amplifying the electromagnetic radiation.
3. illuminating the object with infrared light.
4. using infrared filters.

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24
The electromagnetic radiation that causes tanning?

1. can produce cancer.
2. rarely passes through glass windows.
3. is absorbed by ozone.
4. all of the choices

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25
Maxwell developed his theory of electromagnetism
by combining previous discoveries. He added his
own original hypothesis that?

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.

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26
Of the various types of electromagnetic
radiation, which is the most penetrating through
all forms of matter?

1. infrared
2. gamma
3. visible light
4. ultraviolet

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27
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)

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

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28
Temperature variation of different parts of a
person's body can be detected by analyzing the
emission pattern of which type of electromagnetic
radiation?

1. microwave
2. infrared
3. ultraviolet
4. X-rays

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29
Microwave ovens emit a frequency intended to be
in resonance with which of the following?

1. frequency of water molecule
2. size of oven compartment
3. frequency of metal lining of oven
4. frequency of food molecules

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30
The phenomenon used by police radar is which of
the following?

1. absorption
2. resonance
3. reflection
4. refraction

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31
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)

1. 6.3 x 102 Hz
2. 9 x 102 Hz
3. 7 x 1014 Hz
4. 10 x 1014 Hz

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32
How is the direction of propagation of an
electromagnetic wave oriented relative to the
associated E and B fields?

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

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33
Microwave radiation is useful in which of the
following?

1. sending phone messages
2. cooking food
3. aircraft navigation
4. All of the choices are valid choices

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34
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)

1. 1.8 x 108 Hz
2. 8.5 x 108 Hz
3. 1.1 x 1011 Hz
4. 7.7 x 1014 Hz

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35
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?

1. 551 kHz
2. 750 kHz
3. 1061 kHz
4. 1520 kHz

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36
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?

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

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37
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
4p x 10-7 T x m/A and c 3 x 108 m/s)

1. 1.0 x 10-7 T
2. 8.4 x 10-3 T
3. 1.2 T
4. 30 T

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38
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)

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

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39
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 4p x 10-7 T x m/A, electric
permittivity 8.85 x 10-12 C2 /N-m2 and c 3 x
108 m/s)

1. 12.4 T
2. 2.70 T
3. 3.00 T
4. 1.30 T

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40
A radio wave signal which transmits at a
frequency of 7.2 MHz has what wavelength? (c 3
x 108 m/s)

1. 41.7 m
2. 4.2 m
3. 28.8 m
4. 2.4 x 10-2 m

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41
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 4p x 10-7 T x
m/A,electric permittivity 8.85 x 10-12 C2 /N-m2
and c 3 x 108 m/s)

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

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42
Which one of the following scientists first built
and operated devices that could emit and detect
man-made electromagnetic radiation?

1. Hertz
2. Ampere
3. Maxwell
4. Lenz

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43
Which condition of motion must be met with regard
to a charged particle if it is in the process of
emitting electromagnetic radiation?

1. moves at constant velocity
2. accelerates
3. moves at the speed of light
4. moves parallel to a uniform magnetic field

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44
The electric field, E, in an electromagnetic wave
is oriented in what direction with respect to its
associated magnetic field, B?

1. E parallel to B
2. E anti-parallel to B
3. E perpendicular to B
4. E at a 45 angle to B

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45
Which one of the following scientists made the
theoretical prediction that electromagnetic waves
travel through a vacuum at the speed of light?

1. Hertz
2. Faraday
3. Maxwell
4. Lenz

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46
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)

1. 9.0 x 104 m
2. 4.5 x 104 m
3. 6.0 x 104 m
4. 1.0 x 104 m

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47
In order to keep its food hot, a restaurant will
place it under which type of lamp?

1. infrared
2. visible light
3. ultraviolet
4. X-ray

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48
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 4p x 10-7 T x m/A and c 3 x 108
m/s)

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

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49
Glass panes are opaque to a certain type of
radiation which passes through quartz. What type
of radiation is it?

1. microwave
2. gamma
3. X-ray
4. ultraviolet

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50
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?

1. 62
2. 31
3. 5.2
4. 0.6

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51
An electromagnetic wave is made up of which of
the following oscillating quantities?

1. electrons only
2. electric fields only
3. magnetic fields only
4. electric and magnetic fields

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52
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.

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

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53
In order of increasing frequency, which of the
following is correct?

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

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54
Find the resonant frequency for a series RLC
circuit where R 10W, C 5 µF, and L 2 mH.

1. 998 Hz
2. 1.592 kHz
3. 2.45 kHz
4. 11.3 kHz

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55
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?

1. 100 W
2. 500 W
3. 1000 W
4. 2 W

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56
What is the average power dissipation in a series
RC circuit if R 5 kW, C 2 µF, and V 170
cos 300 t?

1. 0.93 W
2. 2.74 W
3. 28.2 W
4. 157 W

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57
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?

1. 6
2. 70
3. 920
4. 9200

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58
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?

1. 4
2. 2
3. 1/2
4. 1/4

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59
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?

1. 1.0 A
2. 1.8 A
3. 24 A
4. 1000 A

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60
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?

1. 0.09
2. 1.8
3. 32
4. 69

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61
In an ac circuit, the ratio of average current to
maximum current is?

1. zero
2. 0.5
3. 0.707
4. 1.0

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62
The current in an inductor connected to an ac
voltage source lags the voltage. This lag is
caused by?

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

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63
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?

1. 88 watts
2. 132 watts
3. 238 watts
4. 323 watts

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64
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?

1. 0.8 microfarads
2. 1.6 microfarads
3. 2.4 microfarads
4. 3.4 microfarads

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65
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?

1. 25 V
2. 63 V
3. 90 V
4. 125 V

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66
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?

1. 48 V
2. 88 V
3. 95 V
4. 285 V

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67
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?

1. 22
2. 28
3. 37
4. 43

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68
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?

1. 4.3 A
2. 6.0 A
3. 10.3 A
4. 17.1 A

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69
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?

1. 2.82 A
2. 4.0 A
3. 5.64 A
4. 2.0 A

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70
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?

1. 200 W
2. 400 W
3. 566 W
4. 800 W

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71
The power factor in an ac series circuit is equal
to which of the following ratios?

1. resistance to inductive reactance
2. capacitive reactance to inductive reactance
3. inductive reactance to capacitive reactance
4. resistance to impedance

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72
In an ac series circuit the capacitive reactance
is 200 ohms and frequency is 100 Hz. What is the
capacitance?

1. 3.2 microfarads
2. 6.28 microfarads
3. 8.0 microfarads
4. 50.0 microfarads

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73
In an ac series circuit the inductive reactance
is 50 ohms and the frequency is 100 Hz. What is
the inductance in the circuit?

1. 80 mH
2. 240 mH
3. 500 mH
4. 740 mH

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74
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?

1. 159 Hz
2. 318 Hz
3. 637 Hz
4. 530 Hz

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75
Consider an ac series circuit containing a coil,
capacitor and resistance. Tripling the frequency
will change the inductive reactance by what
factor?

1. 1/3
2. 1.0
3. 1.73
4. 3.0

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76
Consider an ac series circuit containing a coil,
capacitor and resistance. Tripling the frequency
will change the capacitive reactance by what
factor?

1. 1/3
2. 1.0
3. 1.73
4. 3.0

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77
Consider an ac series circuit containing a coil,
capacitor and resistance. Tripling the frequency
will change the circuit's impedance by what
factor?

1. 1/3
2. 1.0
3. 3.0
4. Information is insufficient to determine answer

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78
The rate of heat dissipation in an ac circuit
with resistance, R, and effective current, I, is
given by which of the following?

1. 0.5 x I2 R
2. I2 R
3. 2.0 x I2 R
4. 4.0 x I2 R

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79
Resonance occurs in an ac series circuit when
which of the following conditions is met?

1. resistance equals capacitive reactance
2. resistance equals inductive reactance
3. capacitive reactance equals inductive reactance
4. capacitive reactance equals zero

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80
The power dissipated in an ac series circuit
increases as the phase angle approaches what
value?

1. zero
2. 45
3. 90
4. 180

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