In an intrinsic semiconductor, the number of free electrons
A. Equals the number of holes
B. Is less than the number of holes
C. Is greater than the number of holes
D. Impossible to say
E. None of the above
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A device that converts mechanical into electrical energy is?
A. solar cell
B. thermocouple
C. chemical cell
D. generator
E. None of the above
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Which one of the following kinds of materials has the lowest permeability?
A. A diamagnetic material
B. A paramagnetic material
C. A feiTomagnetic material
D. All of the above
E. None of the above
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The total impedance of a parallel RLC circuit:
A. always increases as the applied frequency increases
B. is equal to the sum of the values of resistance, inductive reactance and capacitive reactance
C. always decreases as the applied frequency increases
D. is maximum at the resonant frequency
E. None of the above
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The rise time of a pulse waveform is the time required for the voltage to rise:
A. from zero to its rms value
B. from zero to its peak value
C. from 10% of the peak value to 70.7% of the peak value
D. from 10% of the peak value to 90% of the peak value
E. None of the above
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For a pure capacitor:
A. ac current and voltage are exactly in phase
B. ac current leads the voltage by 90 degree
C. ac current is converted to dc voltage
D. ac current lags the voltage by 90 degree
E. None of the above
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The component that forms the electrical connection between the rotating coil of wire in a motor and the external source of electrical energy is called the:
A. rotor
B. armature
C. battery
D. commutator
E. None of the above
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In a pure inductor:
A. ac current leads the voltage by 90 degree
B. ac current and voltage are exactly in phase
C. ac current lags the voltage by 90 degree
D. ac current is converted to dc voltage
E. None of the above
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Waveforms are graphs that show:
A. frequency on the vertical axis and amplitude on the horizontal axis
B. amplitude on the vertical axis and frequency on the horizontal axis
C. amplitude on the vertical axis and the passage of time on the horizontal axis
D. the passage of time on the vertical axis and amplitude on the horizontal axis
E. None of the above
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When the collector current increases, what does the current gain do?
A. decreases
B. stays the same
C. increases
D. any of the above
E. None of the above
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How many types of flow are there in a semiconductor?
A. 0
B. 1
C. 2
D. 3
E. None of the above
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Which one of the following devices is most often used for measuring opposition to current flow in a circuit?
A. Ammeter
B. Voltmeter
C. Ohmmeter
D. Wattmeter
E. None of the above
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What form of energy is used to maintain an imbalance of charges between the terminals of a battery?
A. Electronical energy
B. Mechanical energy
C. Chemical energy
D. Solar energy
E. None of the above
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Which one of the following statements best applies to a parallel RLC circuit?
A. The voltage waveform for each component always has the same amplitude and phase as the applied voltage
B. The sum of the current is always less than the applied current
C. The current waveform for each component always has the same amplitude and phase as the applied current
D. All of the above
E. None of the above
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The equivalent of 1 micro A is:
A. 10000A
B. 1000 A
C. one-millionth of an ampere
D. one million amperes
E. None of the above
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Which one of the following statements best describes magnetic hysteresis?
A. Hysteresis is the amount of magnetic flux that is not confined to the core material of an electromagnet
B. Hysteresis is most apparent when a steady amount of current is lowing through the coil of an electromagnet
C. Hysteresis is most apparent when the current through the coil of an electromagnet changes frequently
D. Hysteresis is most apparent when the core material is saturated
E. None of the above
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Which one of the following phrases best describes residual magnetism?
A. Magnetism that remains in the core of an electromagnet after the current through the coil is turned off
B. The force of attraction between the poles of a permanent and temporary magnetic field
C. The amount of magnetic flux that is not confined to the core material of an electromagnet
D. The circular magnetic field that surrounds a conductor carrying a current
E. None of the above
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A transformer has a primary voltage of 120 V rms and a secondary voltage of 25 V rms. If the secondary current is 1A rms, what is the primary current?
A. 7.8 mA
B. 208 mA
C. 200 mA
D. 300 mA
E. None of the above
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Household light bulbs have a given power rating, and they operate at 120 V. Which one of the following equations most directly provides the current rating of these light bulbs?
A. P = I2 R
B. P = IE
C. P = E2 /R
D. I = P/E
E. None of the above
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Which one of the following phrases most accurately describes a purely inductive circuit?
A. Resistances provide the only opposition to current flow
B. Inductive reactance provides the only opposition to current flow
C. Combinations of resistance and inductive reactance provide any opposition to current flow
D. The ac voltage lags the current by 90 degree
E. None of the above
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