Electronics and the Letter "F" Quiz

Answer: Frequency

In 1960, the term "hertz", abbreviated Hz, was adopted officially for use, replacing "cycles per second". It is named after German physicist Heinrich Rudolf Hertz (1857-1894). Quite often, kilohertz (1000 Hz), megahertz (1000 kHz) and gigahertz (1000 MHz) are used to describe a frequency.

Answer: Farad

The unit is named after Michael Faraday (1791-1867), a British scientist famous for his work in electromagnetism. A farad is a rather large value for ordinary use and quite often capacitors are much smaller and measured in micro- (one millionth) or pico- (one millionth of one millionth) farads.

Answer: Field

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.

Answer: Force

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?

Answer: Figure

"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.

Answer: Factor

Shape factor is a unitless number and the lower the number the better performance. A perfect, so-called "brick wall", filter would have a shape factor of one.

Why is selectivity important? How bad would it be if your favorite FM station was being obliterated by one on a neighboring channel? Poor selectivity in your radio might be the culprit. Selectivity is often determined by the characteristics of the radio's filters.

Answer: Fundamental

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.

Answer: Flash

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.

Answer: 0xFFFF

Hexadecimal numbers use the characters 0-9 and A-F, where A = ten, B = eleven and so on. Each column is a power of 16 greater than the column to its right, with the rightmost column the one's column.

The 0x at the start of the number indicates the number is in hexadecimal. This may seem obvious when the number has letters in it (such 0xFFFF) but a number like 32 decimal is represented as 20 hexadecimal so 0x20 is proper.

Answer: Fourier

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.