16.
What frequency range is the High Frequency band?
A. 100 kHz
B. 1 GHz
C. 30 to 300 MHz
D. 3 to 30 MHz
Answer & Explanation
Answer: Option D
Explanation:
The HF band is based on frequencies 3 to 30 Mhz. AM radio stations are in the HF band but normally are stated in kilohertz.
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17.
The first step to getting output from a laser is to excite an active medium. What is this process called?
A. Pumping B. Exciting
C. Priming D. Raising
Answer & Explanation
Answer: Option A
Explanation:
A collection of atoms or molecules that can be excited to a higher energy state is called an active medium. Before lasing can occur, the active media is “pumped”. The process of raising the atoms in the active media from a lower energy state to a higher state is like pumping water up from a well.
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18.
What is the relationship between resistivity r and conductivity s?
A. R = s2
B. R = s
C. R > s
D. R = 1/s
Answer & Explanation
Answer: Option D
Explanation:
No answer description available for this question. Let us discuss.
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19.
Which motor is NOT suitable for use as a DC machine?
A. Permanent magnet motor
B. Series motor
C. Squirrel cage motor
D. Synchronous motor
Answer & Explanation
Answer: Option C
Explanation:
The squirrel cage motor is the only one without any connection to the armature.
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20.
A given signal’s second harmonic is twice the given signal’s __________ frequency…?
A. Fourier B. Foundation
C. Fundamental D. Field
Answer & Explanation
Answer: Option C
Explanation:
A given signal’s second harmonic is twice the given signal’s fundamental frequency. Harmonics are generated when there are non-linearities in an amplifier (there are always non-linearities). The worse the non-linearities, the more harmonics. A signal at 27.5 MHz (approximate frequency for US citizen’s band) would have a second harmonic at 55.0 MHz (on US channel 2!). Can you see why there might be problems? A CB operator might do well to place a low-pass filter on his radio.