Question: What does AC and DC stand for in the electrical field?
Correct Answer Electricity is voltage and current. Voltage is electrical pressure, and current is the flow of charged particles. The difference between alternating current (AC) and direct current (DC) is that the electrons in an AC circuit regularly reverse their direction. In a DC circuit electrons always flow in the same direction.
Question: The FFT, a mathematical process, is used extensively in digital signal processing (DSP). For what word does the second "F" in FFT stand?
Correct Answer FFT stands for Fast Fourier Transform, so the second 'F' stands for "Fourier". Joseph Fourier's (1768-1830) theorem states that any periodic signal with a frequency "f" can be expressed as a (weighted) sum of the sinusoids of frequency "f" and f's harmonics. Yes, even a square wave can be described accurately by a sum of sine waves - if you have enough of them. Square waves can be constructed by summing a sinusoid at the fundamental frequency, f, plus sinusoids at all of f's odd harmonics - 3f, 5f, etc.
Question: Which is a type of Electrically-Erasable Programmable Read-Only Memory?
Correct Answer It's commonly used for MP3 players, computer BIOS code and "thumb" drives. Originally developed in Japan by Toshiba, it has become quite popular for products requiring non-volatile erasable memory. Flash devices have a limited number of erase cycles (typically 10,000 to 1,000,000 cycles) so they're not as good a choice for applications in which the data changes constantly. However, since it has no moving parts (unlike a hard disk) it is an excellent choice for storing the operating code for small personal electronics like PDAs, cell phones, digital cameras, and the data in items like MP3 players.
Question: A given signal's second harmonic is twice the given signal's __________ frequency...?
Correct Answer 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.
Question: Voltage is sometimes referred to as EMF, or Electromotive...?
Correct Answer The term EMF, or Electromotive Force, its use now in decline, is attributed to Italian physicist Alessandro Volta (1745-1827). Today we generally use the term "voltage" - can you guess why we call it that?
Question: "FET" is a type of transistor, Its full name is ________ Effect Transistor...?
Correct Answer The terminals of FETs are called gate, drain and source. You might be more familiar with bipolar junction transistors (BJTs), which have terminals called base, collector and emitter. FETs were conceptualized first, but BJTs were easier to produce and so developed sooner.
Question: When measuring the characteristics of a small-signal amplifier, say for a radio receiver, one might be concerned with its "Noise..."?
Correct Answer "Noise figure" is one critical parameter for determining the "quality" of a low-noise, small-signal, amplifier, and perhaps more importantly, the sensitivity of the overall receiver system. It is especially important for VHF (very high frequency) - and higher frequency - designs where most of the undesired "noise" (noise that masks or overpowers the desired signals) is generated internal to the electronics itself. In HF (high frequency) applications, atmospheric noise plays a much larger role in determining overall useful sensitivity, so a circuit's "noise figure" is less important.