Pushing a button can send current into an electromagnet to magnetize an iron core and attract an iron clapper {doorbell}|. Clapper movement breaks electric circuit, attraction ceases, and spring pulls clapper back to resting position. For continuous button press, circuit completes again. Clapper goes back and forth, striking bells. For doorbell chimes, iron core attaches to spring. Clapper hits one metal tube when pressing doorbell button and springs back to hit other tube upon releasing button.
Electric razors {electric razor}| have a thin perforated plate over rotating or oscillating blades, to scissor off hair that enters plate [1910].
Platforms {elevator, lift}| can raise and lower. Elevator cars ride in vertical guide rails.
hydraulic
Hydraulic elevators have small cages or closets at piston top, resting in cylinders filled with oil. Pump applies pressure to fluid to raise elevator and reduces pressure to lower elevator. Hydraulic elevators have speed of one floor per second.
electric
Electric elevators [1887] use an electric induction motor at top to pull cables through a pulley {sheave}. Elevator car hangs on one pulley side, and a large counterweight hangs from other side. Elevators have a brake. Switches just before floors tell electric motor to slow. Switches at floors tell motor to stop. Electric elevators allowed skyscrapers.
In moving stairs {escalator}|, separate stairs ride on two bottom wheels in a track and two top wheels in another track. The parallel tracks slope to keep stair level. At ends, a comb scoops out anything on stairs. Electric motor at stair tops connects by chain to chairs. Rubber belts loop over handrails.
Garage opening {garage opener}| can use a radio transmitter. Garage door has a radio receiver and an electric motor.
Holders {garbage disposal}|, with sharp-edged slats around lower edge, can use an impeller to crush garbage against slats. Garbage bits drain away in running cold water. Paper does not crush well. Do not grind paper, metal, and glass.
Iron trains can ride on magnetic fields on iron tracks, using repulsion from below or attraction from above {magneplane}|.
Machines {sewing machine}| can sew.
needle and thread
Sewing-machine needles have an eye three millimeters from point. Thread comes from spool, through tension control knob, through needle eye. Second thread comes from different spool {bobbin}, underneath needle and material.
process
Needle enters material and goes through to bobbin. Hook snags thread and loops thread around bobbin, to make lock stitch. As needle rises, lever {thread take-up lever} pulls thread tight. The lever also pulls a length of thread from spool. After needle leaves material, a rough plate rises from below, squeezes material between plate and needle guide plate above, and pushes material forward one stitch length.
On printing devices {plotter}|, paper can scroll past a pen vibrating from electric-current waves. Time axis is along scrolling direction, and amplitude axis is across paper.
Two metal strips, usually copper and chromium, can align side-by-side {thermostat}|. Temperature increase expands metals at different rates, and strip curls, moving a dial.
Telegraph systems {ticker}| can punch tape, or make similar electronic displays, to indicate stock prices and trades.
Devices {changer} {turntable}| {record player} can play one record at a time or automatically play a stack of records.
speeds
Records can turn at 16 2/3, 33 1/3, 45, or 78 revolutions per minute (rpm), to match speed at which master disc was cut.
needle
Needle holder {cartridge, record} is at one arm end, and needle rests in record groove. Pivot is on other arm {tonearm} end, for balance. Needles can be steel, sapphire, or diamond. Needle vibrates in groove and generates an electric signal.
Crystal or ceramic cartridges make electric signals by piezoelectric effect. Magnetic cartridges make electric signals by a magnet moving in a wire coil.
amplification
Wires carry signal to a device {preamplifier}, which reconverts signal to proper high and low frequency strength {equalization}, not needed for ceramic cartridges. Preamplifier has knobs to control loudness {volume control}, high frequencies {treble control}, low frequencies {bass control}, and loudness between two stereo speakers {balance, speaker}.
speaker
Amplifiers increase signal power and send signals to a solenoid connected to a paper cone {speaker, audio} {loudspeaker}. Speakers are typically the least-accurate music-system part, so they are the most-important part.
sound
Electrical-signal shape can change {sound, distortion}. High fidelity limits total distortion to less than 15%.
Sound-frequency range has a loudness range {frequency response}. Loudness is in decibels. A three-decibel difference doubles loudness. Humans can detect a one- decibel difference.
Adding machines {adding machine}| can be for adding, subtracting, multiplying, dividing, and other algorithms. Adding machines have gears, which engage in sequences depending on selected numbers and functions.
Old calculating devices used mechanical gears and shafts to solve differential equations {differential analyzer}| [1830].
induction coil {spark coil}|.
Spark traverses air or dielectric {spark gap}| between two conductors.
To spark sparkplugs {magneto}|, a rotating magnet generates voltage.
Spinning cylinders {centrifuge}| can hold tubes with fluid, so denser parts sink to tube bottom.
Centrifuges {ultracentrifuge}| can spin at 100,000 rpm.
Dish washing machines {dishwasher}| can use spinning hot-water jets to splash dish racks.
Machines {washing machine}| can have a tub within a tub. Water enters outer tub until timer switches water off, or float-control rises enough, to close inlet valve. Motor attaches to finned central piece {agitator, washer}. Agitator turns back and forth, using a linkage. Electric timer controls wash-rinse-spin cycle, which uses a camshaft and cams to depress switches. A pump drains water from tub.
Fans {propeller-type fan} can cut air at an angle and push a spiral air wedge straight in front of fan blade. Propeller fans {fan} can move back and forth, using a crank linked to motor. Fans {centrifugal fan} can use a paddle wheel {impeller} in a casing, pull air in at center, and push air out straight.
To compress {compressor, air}| {air compressor}, a pump fans air into a sealed tank, thus building pressure. Sealing pump and fan prevents leaking air.
To dry clothes {dryer}|, a large drum turns on side using an electric motor, while a fan blows heat from gas flame or electric coils through drum holes. Air goes out exhaust flue, through filter to catch lint. For exhaust that must stay inside building, cold water pipes receive exhaust, and water and lint condense on pipes and drain away together.
To dry hair {hair dryer}|, an electric motor runs a fan that blows air over heater-coil Nichrome wire.
To sweep {vacuum cleaner}|, a fan causes vacuum, which sucks up dust into a filter.
Small propellers can suck liquid down, drawing air and food into turning blades {blender}|. Sealed propeller shaft prevents leaking.
Household machines {mixer, machine}| {electric mixer} can use two beaters turned by an electric motor. Beaters cross each other's path, without touching, and suck air into turning liquid.
Machines {alternator}|, opposite of generators, can create direct current.
generator {dynamo}|.
Metal rings {slip ring}| can have alternating conducting and insulating regions and transfer electricity to or from rotor in alternators and motors.
Moving-belt friction can create static electricity of more than one hundred thousand volts {van de Graaf generator}|.
In cooling devices {air conditioner}|, a pump {compressor, air conditioner} compresses hot Freon or other easily liquefied gas. As fan blows air from outside, or water, goes, over small tubes, gas cools, and so liquefies. Then liquid goes through a tiny opening {constriction}, causing gas to expand and thus cool. Cool gas passes through tubing coils, through which fan blows room air. Room air heat passes to cool gas, which then compresses to start cycle again. Air conditioners have ratings, in British Thermal Units (BTU), of how much heat they can remove from air.
Refrigerators {freezer}| can be colder.
Cooling devices {refrigerator}| can remove heat from inside a box. Refrigerators use a gas, such as Freon, which easily liquefies with pressure. The liquefied gas in tubes inside box absorbs heat and expands. Machines {compressor, refrigerator} can compress hot gas back to liquid and send liquid through tubes outside box. A blower blows air over tubes to remove heat.
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Description of Outline of Knowledge Database
Date Modified: 2022.0225