How Everything Works   Page 75 of 160 (1595 Questions and Answers) Printer Friendly Version

741. Is it true that Tesla invented a way to send electrical power without the use of power lines? If so, how? - BS
Yes. Tesla found that the alternating electromagnetic fields around a large high frequency transformer could propel currents through wires or lamps that were located at a moderate distance from the transformer. But this technique of using the alternating fields near a transformer to provide power aren't very practical—there is too much power wasted through radiation or in heating things that aren't meant to be heated.

742. What is white noise? - AT
Acoustic "white noise" is a collection of random sounds that together have the same volume at every frequency or pitch. It's defined more accurately as having the same amount of power in each unit of its bandwidth, so that the acoustic power between 20 and 21 cycles per second is the same as the acoustic power between 500 and 501 cycles per second.

743. How does a TV or VCR remote control work? Is it infrared light or a laser? How does the TV or VCR know what to do with the light it receives from the remote? — FC, Lafayette, CA
The remote unit communicates with the TV or VCR via infrared light, which it produces with one or more light emitting diodes (LED). The most remarkable feature of this communication is that the TV or VCR is able to distinguish the tiny amount of light emitted by the LED from all the background light in the room. This selectivity is made possible by blinking the LED rapidly at one of two different frequencies. Since it's unlikely that any other source of light in the room will blink several hundred thousand times per second and at just the right frequency, the TV or VCR can tell that it's observing light from the remote. The remote sends information to the TV or VCR by switching back and forth between the two different frequencies. For example, it may use the higher frequency to send a "1" bit and the lower frequency to send a "0" bit. The remote sends a long string of these 1's and 0's, and the TV or VCR detects and analyzes this string of bits to determine (1) whether it's directed toward the TV or VCR (an address component in the information) and (2) what it should do as the result of this transmission (a data component in the information). Assuming that the string of bits was intended for the TV or VCR, its digital controller (a simple computer) takes whatever action the data component of the transmission requested.

744. How was Newton able to prove inertia with gravity and friction still being present? Why didn't people think he was crazy? Did he have some type of vacuum or something? - JP
Actually, it was Galileo who first realized that objects have this tendency to continue moving at a steady rate in a straight-line path—what we call "inertia." He deduced this fact by studying the motions of balls on ramps. He noted that a ball rolling down a slight incline steadily picked up speed while a ball rolling up a slight incline steadily lost speed. From these observations he realized that a ball rolling along a level surface would roll at a steady speed indefinitely, where it not for friction and air resistance. He was aware that friction, air resistance, and gravity were disturbing the natural motions of objects and had figured out a way to see beyond them. But it wasn't until Newton took up this sort of study that the idea of forces and their effects was properly developed. Overall, it took almost two thousand years, from Aristotle to Newton, for the incorrect idea that objects tend to remain stationary when free of forces to be replaced with the correct idea that objects tend to continue at constant velocity when free of forces.

745. When friction is made by two atoms rubbing — it makes heat. But how and why? — GN, Marine City, MI
When two surfaces slide across one another, some of the mechanical energy in those surfaces is converted to thermal energy (or heat). That's because the surfaces are microscopically rough and their atoms collide as the surfaces slide pass one another. Each time a collision occurs, the atoms that collide begin to vibrate more vigorously than before. In this process, the surfaces lose some of their overall mechanical energy but the atoms gain some randomly distributed local vibrational energy—more thermal energy. Those surface atoms become hotter. As the sliding continues, large regions of the surfaces become hotter and the surfaces lose much of their energy. If you don't push them to keep them sliding across one another, they'll come to a stop as all their mechanical energy is converted into thermal energy.

746. Where does the wax from a burning candle go? Also, why do beeswax candles burn virtually completely, leaving no wax behind at all? — SC, Rhode Island
The wax molecules in the candle react with oxygen in the candle flame and are converted into water molecules and carbon dioxide molecules. That reaction is associated with combustion and it releases energy so that the candle produces light and heat. The molecules formed by this combustion drift off into the air.

Normal candle wax (paraffin wax) consists of relatively large hydrocarbon molecules. Each molecule in paraffin is a chain of between 30 and 50 carbon atoms that are surrounded by hydrogen atoms. Because its molecules are fairly long and they stick together reasonably well, paraffin is a firm, crystalline solid. If the chains were shorter, say 20 to 30 carbon atoms long, the material would be softer—it would be a liquid-like wax known as petroleum jelly. If the chains were much longer, say 2000 to 3000 carbon atoms long, the material would be firmer—it would be a solid known as polyethylene. Still shorter chains are used in machine oil, diesel fuel, unrefined gasoline, and finally petroleum gases such as propane and methane. The shorter the chain, the softer, thinner, and more volatile the hydrocarbon is at any given temperature. All of these hydrocarbon molecules can burn completely, leaving only water molecules and carbon dioxide. In a candle, the heat of the flame vaporizes the wax molecules—they become a gas—and they then burn completely in the flame itself. As long as the wax doesn't drip away from the flame, the flame will consume it all completely and leave no ash or wax. Although the structure of the molecules in beeswax is slightly different from that in paraffin, beeswax also vaporizes from the heat of the flame and then burns completely.

747. What is an electric field and how does it affect us? — MT, Brampton, Ontario
Electrically charged particles exert forces on one another. For example, a negatively charged particle attracts a nearby positively charged particle and repels another negatively charged one. These attractions and repulsions are mediated by electric fields that are created by those charges. By this statement, I mean that the negatively charged particle creates an electric field around itself and this electric field is what ultimately exerts forces on the other two charges—attracting the nearby positively charged particle and repelling the negatively charged one. Whenever an electrically charged particle finds itself in an electric field, it experiences a force. The direction of that force depends on its electric charge (either positive or negative) and on the direction of the electric field (which may have somewhat different directions at different points in space). The strength of that force depends on the amount of electric charge on the particle and on the strength of the electric field (which can vary from nothing at all to extremely strong).

But while electric fields always exist around charged objects and exert forces on any other charged objects that enter them, electric fields can also exist far away from charges. Electromagnetic waves contain electric and magnetic fields (the magnetic equivalents of electric fields) and these two fields sustain one another as the wave travels. Although electromagnetic waves are created and destroyed with the help of charged particles, they can travel alone and without any nearby charged particles to assist them.

While electric fields exert forces on the charged particles in our bodies, the response of those charges isn't likely to injure us. When you are exposed to an electric field, there is a subtle rearrangement of electric charges on the surface of your body that then creates its own electric field. The result is that there is essentially no electric field inside you. Only when you are exposed to extremely strong electric fields, and spark and currents begin to flow through you, is there any significant effect to you.

748. How are the paints made that artists (like Rembrandt and Monet) used in the past? — SB, Oedenrode, The Nederlands
These paints consisted principally of a pigment and a drying oil binder. The pigment was usually a colored powder that didn't dissolve in the oil. Historically, these pigments were materials collected from nature. The drying oil binder was usually linseed oil, obtained from the seed of the flax plant and a byproduct of the linen industry. Like most organic oils, linseed oil is a triglyceride—it consists of a glycerin molecule with three fatty acid chains attached to it. But while in typical animal or tropical plant oils the carbon atom chains of the fatty acids are completely decorated with hydrogen atoms (saturated fats) or almost completely decorated (monounsaturated fats), the carbon atom chains in linseed oil are missing a significant number of hydrogen atoms (polyunsaturated fats). The polyunsaturated character of linseed oil makes it vulnerable to a chemical reaction in which the chains stick permanently to one another—a reaction call polymerization. With time and exposure to air, the molecules in linseed oil bind together forever to form a real plastic! This "drying" process takes weeks, months, or years, depending on the chemicals present in the paint. It can be accelerated by the addition of catalysts—chemicals that assist the polymerization process but that don't become part of the final molecular structure of the plastic.

749. How do rotary telephones work? — JG, DeSoto, Kansas
As your finger turns the dial of the telephone, you wind a spring and store energy in that spring. When you remove your finger, the spring unwinds and its stored energy drives the dialing mechanism. This mechanism consists of a cogged wheel and a switch, as well as a centrifugal governor. As the dial unwinds, the cogged wheel turns and it's cogs close and open a switch one time for each number on the dial. For example, if you dial a "6", the switch closes briefly 6 times. For a "0", the switch closes 10 times. Each time the switch closes during this action, it "hangs up" the telephone briefly. The switching system at the telephone company recognizes these brief hang-ups as signals for establishing the connection. The centrifugal governor controls the rate at which the dial unwinds and makes sure that the pulses coming from the telephone occur at a uniform rate.

750. Warner Brothers has been misleading children! The coyote and the anvil hit the ground at the same time!
You're exactly right. Occasionally one of those cartoons shows the coyote falling with the anvil directly above his head and the distance between them remaining constant, which is what should happen (ignoring air resistance). But more often, the coyote falls much faster than the anvil, hits the ground first, and is then pounded by the anvil. It sure would be neat to live in a cartoon—the laws of physics just wouldn't apply.

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