Which consists of two plates separated by a dielectric and can store a charge?
Answer: B
A capacitor is two plates separated by a dielectric, and stores charge.
Its capacitance \( C = \varepsilon A / d \) grows with plate area and with the permittivity of the dielectric, and falls as the plates are moved apart. The energy stored is \( \tfrac12 CV^2 \).
Please log in or register to report this question.
What was the active medium used in the first working laser ever constructed?
Answer: C
The first working laser used a ruby rod.
Theodore Maiman built it at Hughes Research Laboratories in 1960, pumping a synthetic ruby cylinder with a photographic flash lamp to produce a deep red pulse at 694 nm.
Please log in or register to report this question.
Compact discs, (according to the original CD specifications) hold how many minutes of music?
Answer: A
A compact disc holds 74 minutes of music under the original specification.
The story is that Sony's Norio Ohga insisted the disc hold Beethoven's Ninth Symphony complete, which fixed the diameter at 120 mm. Later discs stretched the format to 80 minutes.
Please log in or register to report this question.
The electromagnetic coils on the neck of the picture tube or tubes which pull the electron beam from side to side and up and down are called a...?
Answer: B
The deflection coils on the neck of a picture tube are called the yoke.
They generate magnetic fields that sweep the electron beam horizontally and vertically, scanning it across the screen line by line to build the picture.
Please log in or register to report this question.
The average power (in watts) used by a 20 to 25 inch home color television is...?
Answer: A
A 20 to 25 inch colour television draws about 70 to 100 watts.
Most of it goes to the electron gun and the deflection circuits. A modern LED set of the same size uses a fraction of that.
Please log in or register to report this question.
After the first photons of light are produced, which process is responsible for amplification of the light?
Answer: B
Light in a laser is amplified by stimulated emission.
A passing photon triggers an excited atom to emit a second photon identical to it in frequency, phase and direction, so one photon becomes two, two become four, and the beam builds up. The acronym stands for light amplification by stimulated emission of radiation.
Please log in or register to report this question.
In which decade did the first transatlantic radio broadcast occur?
Answer: D
The first transatlantic radio broadcast occurred in the 1900s.
Marconi received the letter S in Morse across the Atlantic in December 1901, and the first transatlantic transmission of speech and music followed a few years later.
Please log in or register to report this question.
'.MPG' extension refers usually to what kind of file?
Answer: C
A .MPG file is a movie file.
MPEG, the Moving Picture Experts Group, defines the compression standards used for video. MPEG-1 gave the Video CD, MPEG-2 the DVD and digital broadcasting, and MPEG-4 most modern streaming.
Please log in or register to report this question.
Who created Pretty Good Privacy (PGP)?
Answer: A
Phil Zimmermann created PGP, Pretty Good Privacy, in 1991.
It brought strong public-key encryption to ordinary users. Because encryption was then classed as a munition in the United States, Zimmermann was investigated for three years over its export.
Please log in or register to report this question.
What does AM mean?
Answer: C
AM stands for amplitude modulation.
The amplitude of a carrier wave is varied in step with the signal. It was the first practical method of broadcasting speech and music, and it carries further than FM but is more affected by electrical interference.
Please log in or register to report this question.
