Science and Technology Section 1
Practice and master this topic with our carefully crafted questions.
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?
Amplitude modulation was the first type to be used in radio. It works well with HF and morse code.
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RF is radio frequency. IF is intermediate frequency used inside the TV for processing. AF is audio frequency. SAP is second audio program which may have another language or other soundtrack as an option to the main soundtrack.
According to many stories surrounding the origin of the compact disc, 74 minutes was settled on because it would comfortably contain all of Beethoven's 9th symphony on one disc. Although some stories reference a specific Sony higher-up who claimed this as his favorite piece of music, stories differ. All that's known for sure is that Sony insisted on this and won out over Phillips' original 60 minute proposal.
Spontaneous emission is what you see with most "glow in the dark" toys. You excite the toy by exposing it to bright light, then the toy glows in the dark by spontaneously emitting photons as the excited atoms relax back down to their normal state.
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About the same as as the most popular light bulb size.
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.