382.The atoms inside the two materials are arranged in different ways, and this is what gives the two allotropes their completely different properties.
383.Electricity generation is the process of converting non-electrical energy to electricity. It is the first process in the delivery of electricity to consumers, followed by electric transmission and distribution, which is managed by the electric delivery company.
384.In parallel circuits, the loads are connected across the power line to form branches.
385.Once the architecture of the network has been developed and the parameters chosen the training could begin.
386.Metallic aluminum seems not to be acted upon by air or water, or many other chemical agencies.
387.That these questions should have been raised was only to be expected.
388.A body at rest remains at rest unless it is acted upon by an external force.
389.If the body is free, it will fall toward the earth with acceleration. We say, therefore, that it is acted upon by a force, the force of gravity, or weight, of the body.
390.If instead of using a simple wire connected to a galvanometer, we were to use a wire carrying an electric current, the wire will be found to experience a force urging it sidewise across the magnetic flux.
391.Great care should always be exercised never to allow a larger current to flow through an ammeter than it is intended to carry.
392.The kinetic energy has to be used up in overcoming friction, or some resistance, or in doing some form of work before the velocity can be reduced to zero.
393.The asymmetrical cryptography method has been proven to be secure against computationally limited intruders.
394.It was thought at the time that radio waves in the atmosphere traveled in straight lines and that they therefore, would not be useful for over the-horizon communication. That opinion did not discourage Marconi, however, who became the first to demonstrate the transmission of radio waves over long distances.
395.The calculated energies of the neutrons are affected by the errors listed above.
396.It should be noted that the amplification ratio may be changed by changing the grid bias voltage.
397.The two stators are wound in the same direction so as to give a field in the same direction and the rotor has a field which reverses twice per cycle because it is connected to brushes, which are omitted here.
398.The basic principles of induction heating have been understood and applied to manufacturing since the 1920s.
399.The ways of obtaining information on markets and prices from the press and from government publications have already been explained.
400.Electrostatics was originally discovered when the ancient Greeks noticed that small pieces of straw were drawn to the surface of amber after it had been rubbed.
401.The calculated energies of the neutrons are affected by the errors listed above.
402.When the compass is placed closer to one or the other of the two conductors, one above and the other below the compass, the needle will be influenced by the conductor nearest to it.
403.The high-vacuum phototube is defined as one which is «evacuated to such a degree that its electrical characteristics are essentially unaffected by gaseous ionization».
404.Under perfect conditions, a body may be forced to hold its charge for some little time, but the preparations would have to be elaborate.
405.The loads operate independently of each other, and therefore a break in any one branch does not prevent the line voltage from being applied to the remaining branches. The result is that one path (branch) can be open with the load not receiving current without the other loads being affected, as in the newer strings of holiday lights.
406.Using the tank of water relationship, current is the equivalent of the flow of water through the pipe with the flow being the same throughout the pipe.
407.A number of materials are very weakly attracted by a magnetic field, having permeabilities slightly greater than that of free space; these materials are called paramagnetic.
408.The newton is defined as the force which, when applied to a mass of one kilogram, gives it an acceleration of one metre per second squared.
409.Resistance is not affected by frequency with the AC impedance of a resistance being equal to its DC resistance and as a result can not be negative.
410.Depending on the composition of metal or non-metal in the alloy, we have different types of alloys being formed.
411.When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire.
412.As with other hazardous materials being transported, packages of radioactive materials are labelled in accordance with the requirements of national and international regulations.
413.Not only will you find highlights of important technological contributions, you will also learn about the tribulations and excitement that accompany the discoveries of these early masters. Included are nearly 100 rare photographs from museums around the world.
414.J. J. Thomson deflected an electric current flowing through a vacuum, using a strong electric field, and, by seeing in which direction the beam was deflected, proved that it was made up of tiny negative electric charges, or electrons.
415.Remember to use the correct decimal equivalent when dealing with numbers that are preceded with milli (m), micro (m) or kilo (k).
416.While constructing a railway in 1936 near Baghdad, workers uncovered what appeared to be a prehistoric battery, also known as the Parthian Battery.
417.By varying the characteristics of a radio wave—frequency, amplitude, or phase—these waves can be made to communicate information of many types, including audio, video, and data.
418.When considering the truth of quantum electrodynamics in its new form one has first of all to realize the extraordinary success of this theory in giving results in agreement with the experiments.
419.Armed with a selection of cordless power tools and spare batteries, a repairman can often complete a day's work order without having to stop to charge batteries or string an extension cord.
420.One simple way to think about a generator is to imagine it acting like a pump pushing water through a pipe. Only instead of pushing water, a generator uses a magnet to push electrons along.
421.Inside the capacitor, the terminals connect to two metal plates separated by a dielectric (an insulating substance such as ceramic or glass that is highly resistant to electric current) that keeps the plates from touching each other and allows them to hold opposite charges, maintaining an electric field.
422.When many people use a wireless service provider’s network at the same time and its capacity is strained, other customers trying to connect may hear a “busy signal” instead of being able to complete their calls.
423.Having been filtered by the resonant circuit at the front end of a radio receiver the incoming signal is then amplified before undergoing a process called demodulation.
424.While demonstrating to students the heating of a platinum wire with electricity from a voltaic pile at the University of Copenhagen, Danish physicist Hans Christian Oersted notices that a nearby magnetized compass needle moves each time the electrical current is turned on.
425.In 1895, while conducting research with his step-up transformer, Nikola Tesla had his first indications that time and space could be influenced by using highly charged, rotating magnetic fields.
426.Instead of having a single loop, generators used to supply electricity to homes and businesses have multiple magnets and loops consisting of wires wound around an iron core, similar to an electromagnet. The more loops of wire passing through the magnetic field, the higher the voltage that is created.
427.The principal job of a resistor within an electrical or electronic circuit is to "resist" (hence the name resistor), regulate or to set the flow of electrons (current) through them by using the type of conductive material from which they are composed.
428.The method can be used to trace metallic pipelines, so naturally when operating in a district where buried pipelines are likely to be found, the operator must be on the watch for them.
429.In order to create electric current with enough power to do useful jobs like light and heat our homes and power trains, the magnet inside the generator must rotate at high speed - and this requires an input of energy.
430.In order for your home or a store to use the electricity, it has to be at a lower voltage than on the long-distance lines.
431.To illustrate the importance of understanding the physics of a process in order to develop useful models for it, we can look at two examples where the physics is not yet understood, and thus for which models capable of predicting performance do not exist: high-temperature superconductivity and cold fusion.
432.Electrons are the smallest and lightest of the fundamental particles. They are said to have a negative charge, meaning that they are surrounded by some kind of an invisible field of force that will react in an electrically negative manner with other matter.
433.As there is no direct path (DC path) from the primary coil to the secondary coil, energy is coupled from the primary to the secondary through the magnetic field and the secondary is said to be electrically isolated from the primary.
434.The underlying strategy of our process is to match the optical constants while considering the effects of scattering under different wavelengths.
435.These types of AC circuits are not very efficient, but this attribute is actually well suited to information circuits, since their purpose is to transmit data, rather than electrical power.
436.The purpose of minimizing numerical calculations in both sections of the examinations and providing equations with the free-response section is to place greater emphasis on the understanding and application of fundamental physical principles and concepts.
437.To enhance the generation of electricity from renewable sources and combined heat and power plants, the network operator is generally required to offer a connection to the grid, unless providing access is technically impossible or economically unreasonable.
438.Radio waves are often believed to travel in a straight line like a stone tossed into a still lake.
439.Since living tissues were known to be conductors it was impossible to imagine how an imbalance of charge could exist within an animal and therefore animals could not use electricity for nerve conduction - or to deliver shocks.
440.The sunken ship, thought to have been carrying plunder, from Roman-conquered Greece to Rome, is believed to have sailed from Rhodes
441.Many of the early cell phones were considered to be “car phones,” as they were too large and cumbersome to carry around in a pocket or purse.
442.The assumption that there are forces between electrified and magnetized bodies was found to account for many observations
443.AC electricity was proven to be better for supplying electricity than DC, primarily because the voltages can be transformed.
444.Back in the 19th century, charlatan inventors would pop up from time to time showing off miracle machines that seemed to be able to drive themselves forever. Inventions like this are called perpetual motion machines: they seem to be able to move forever without anyone adding any more energy.
445.Among the many physician specialties, urologists seem to be one group that is very likely to be using a smartphone. That was one of the conclusions that could be drawn from a survey published last year by Bulletin Healthcare, which found that only physician assistants, emergency room physicians, and cardiologists were more likely to use their mobile devices to keep up with industry news. Bulletin estimated that about 31 percent of urologists were likely to use their mobiles for this purpose.
446.This meant that additional components were often required to tune the circuit to the output characteristics required for the tube used.
447.Digital signal processors are designed to be used for audio signal processing, audio and video compression, speech processing and recognition, digital image processing, digital communications, biomedicine, seismology and radar applications.
448.The procedures employed are designed to ensure the protection of the public and the environment both routinely and when accidents occur.
449.How electrical stimulation works is not precisely understood, though it is thought to block the transmission of pain signals along nerves. Electrical stimulation is also thought to provoke the release of endorphins -- the body's natural painkillers.
450.Metals are now known to be primarily elements characterized by atoms in which the outermost orbital shell has very few electrons with corresponding values of energy.
451.This is important because an attacker may try to deceive other secondary users by transmitting from the vicinity of the TV tower, and here the level of the energy of the transmitter will be used in conjunction with the location.
452.To avoid the inevitable confusion resulting from trying to keep track of charge polarity, all discussions of electric charge movement will be described from the perspective of positive charges.
453.The tables giving the installation methods also refer to specific tables to be used to determine the correction factors connected with the group of circuits and conduits.
454.Production is supported by a sophisticated computerized system that provides the ability to satisfy unusual customer requirements by scheduling raw materials, controlling production and speeding deliveries while keeping costs low and maintaining the highest levels of service and quality.
455.To control the arm motion, only the location of the centre of gravity of an object to be grasped would be necessary.
456.The next principle to think about is the number of motions you make throughout a day, whether with your fingers, your wrists, your arms, or your back.
Дата: 2018-11-18, просмотров: 288.