# Technology general knowledge question

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

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.
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

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.
18.

What is the relationship between resistivity r and conductivity s?
A.     R = s2
B.     R = s
C.     R > s
D.     R = 1/s

Explanation:

No answer description available for this question. Let us discuss.
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

Explanation:

The squirrel cage motor is the only one without any connection to the armature.
20.

A given signal’s second harmonic is twice the given signal’s __________ frequency…?
A.     Fourier    B.     Foundation
C.     Fundamental    D.     Field

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.