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The Wurtz Coupling is one of the oldest organic reactions, and produces the simple dimer derived from two equivalents of alkyl halide. The intramolecular version of the reaction has also found application in the preparation of strained ring compounds:
Using two different alkyl halides will lead to an approximately statistical mixture of products. A more selective unsymmetric modification is possible if starting materials have different rates of reactivity
Side products:
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An Aldol condensation is an organic reaction in which an enol or an enolate
ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone,
followed by a dehydration to give a conjugated enone
Aldol condensations are important in organic synthesis, providing a good way to form carbon–carbon bonds. The Robinson annulation reaction sequence features an aldol condensation; the Wieland-Miescher ketone product is an important starting material for many organic syntheses. Aldol condensations are also commonly discussed in university level organic chemistry classes as a good bond-forming reaction that demonstrates important reaction mechanisms. In its usual form, it involves the nucleophilic addition of a ketone enolate to an aldehyde to form a β-hydroxy ketone, or "aldol" (aldehyde + alcohol), a structural unit found in many naturally occurring molecules and pharmaceuticals
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hiiiiCompounds having the same molecular formula, but differing in physical
and chemical properties are known as isomers. This phenomenon is known
as isomerism. The isomers can be identified and distinguished from one another
because of difference in their physical and chemical properties.
a measure of the magnetic strength of a magnet or current-carrying coil, expressed as the torque per unit magnetic-flux density produced when the magnet or coil is set with its axis perpendicular to the magnetic field. Symbol m j Also called magnetic moment
A vector quantity associated with the magnetic properties of electric current loops or, more generally, magnets. It is equal to the amount of current flowing through the loop multiplied by the area encompassed by the loop, and its direction is established by the right hand rule for rotations. It can be thought of as a vector pointing from the south to the north of a magnetic dipole, and is then equal to the length of the dipole times the strength of either of its poles. Also called magnetic moment !!!!!
no . that depends on the permeability of medium around.
The property of self-inductance is a particular form of electromagnetic induction. Self inductance is defined as the induction of a voltage in a current-carrying wire when the current in the wire itself is changing. In the case of self-inductance, the magnetic field created by a changing current in the circuit itself induces a voltage in the same circuit. Therefore, the voltage is self-induced !!!!!
battery eliminatorA battery eliminator is a device powered by an electrical source other than a battery, which then converts the source to a suitable DC voltage that may be used by a second device designed to be powered by batteries.A battery eliminator eliminates the need to replace batteries but may remove the advantage of portability. A battery eliminator is also effective in replacing obsolete battery designs
step down transformer
it is simply a transformer that reduces voltage !!!!!
RADAR Radio Detection And RangingRADAR Royal Association for Disability And Rehabilitation (London, England)RADAR Regional Alcohol and Drug Awareness ResourceRADAR Register of Australian Drug and Alcohol Research (Australia)RADAR Rural AIDS and Development Action Research (Programme, South Africa)RADAR Radio Association Defending Airwave RightsRADAR Reflective Agents with Distributed Adaptive ReasoningRADAR Radio's All-Dimension Audience ResearchRADAR Rights, Availabilities, Distribution, Analysis, and ReportingRADAR Risk Assessment and Decision Analysis Research Group (Queen Mary and Westfield College, London, England)RADAR Resource And Data Activity RepositoryRADAR Removing Aggressive Drivers and Road RageRADAR Reseau Afro-Asiatique pour le Developpement de l'Aviculture RuraleRADAR Radical ArkansasRADAR Retrieve Assess Decide Action Review (decision making process) !!!!!
resolving power
magnifying power
The ratio of the tangent of the angle subtended at the eye by an image formed by an
optical system, to the tangent of the angle subtended at the eye by the corresponding
object at a distance for convenient viewing !!!!!
A thermometer "in a vacuum" will be in thermal equilibrium with theelectromagnetic radiation field surrounding it. You cannot get away from thiseven if the thermometer is in outer space. It will equilibrate with theradiation field to which it is exposed (not just visible but from thelongest wavelength microwave through X-rays and gamma rays. This mode ofenergy exchange occurs even in a "perfect vacuum" since it requires nomedium to transport the energy. So the thermometer will record the averageenergy field. Of course you have to generalize what you mean by the"thermometer". A typical mercury in glass type may not be appropriate forthe measurement.temperature is a property of matter (it is related to how much energy isstored in the mater in the form of motion -- vibrations) and hence doesnot apply to a vacuum.Heat can be transferred by conduction, convection, or radiation. Byputting the thermometer in a (perfect) vacuum you have removed theopportunities for conduction and convection. Radiation is the only pathfor energy transfer and hence temperature change. If the surroundingsof the vacuum container are cooler than the thermometer it will looseenergy to its surroundings by radiation -- though very slowly !!!!!
The straightforward principle behind the Van der Graaf generator is as follows. Electric charges of the same type (either positive or negative) are put onto a moving belt, carried upwards by the belt into a hollow copper dome, and left there. This is a continuous process, the belt collecting charge at the bottom and depositing for storage at the top. As the amount of charge on the dome builds up, its voltage increases.Suppose the dome is to be negatively charged. At the lower end of the machine is an electric generator capable of making a direct current of electricity at a relatively low voltage – about 20,000 volts. To the negative terminal of this generator are attached a number of sharp metal spikes, which of course become negatively charged. They are fixed a short distance away from the moving belt.The charges on the spikes are so densely packed that they are pushed off by fresh charges arriving from the generator. These jettisoned charges are carried by moving air molecules towards the belt which is in effect "sprayed" with negative charges.The belt is made from an insulating material – rubber, silk, or linen – so that the charges stay fixed on the belt as it moves upwards.At the top of the Van der Graaff generator is another set of metal spikes, attached to the inside of the dome. The negative charges on the moving belt repel negative charges (which previously formed the outer parts of metal atoms in the spikes) to the dome. The positive charges left on the spikes are "sprayed" onto the belt where they neutralize the negative charges brought up by the belt. The negative charges repelled from the spikes to the dome fly to the outside of the dome. There is no charge on the inside surface of the dome, so there is nothing to prevent further negative charges coming to it from the spikes.Van der Graaff generator chargeLeft: charging negatively. Right, charging positivelyWhen the voltage difference between the dome and the Earth is a few million volts, it becomes very difficult for the dome to hold its charge. Charges, closely crowded together on the outer surface, repel each other and start to leak away into the surrounding air, or else flow, in a gigantic spark, to Earth. To prevent this, the dome is highly polished so that there are no bumps where denser patches of charge can accumulate. The entire generator is placed in a steel enclosure filled with gas (sulfur hexafluoride or nitrogen) at high pressure. It is more difficult for the charge to leak through high-pressure gas than through ordinary air.The Van der Graaff machine is used to accelerate streams of particles, so that they move quickly enough to produce interesting effects when they hit target atoms. The particles are initially stationary at the top of a long tube reaching from the top of the tube to the ground. When the dome is connected to the top of the tube, an enormous voltage accelerates the electrically charged particles towards the bottom of the tube. Usually the machine accelerates streams of positively charged particles, and the dome must be positively charged to repel the positive charges. To charge the dome positively, the lower spikes are attached to the positive terminal of the 20,000-volt generator.
# the rate of flow of energy or particles across a given surface# a flow or discharge# a substance added to molten metals to bond with impurities that can then be readily removed# excessive discharge of liquid from a cavity or organ (as in watery diarrhea)# a state of uncertainty about what should be done (usually following some important event) preceding the establishment of a new direction of action; "the flux following the death of the emperor"# flow: move or progress freely as if in a stream; "The crowd flowed out of the stadium"# magnetic field: the lines of force surrounding a permanent magnet or a moving charged particle !!!!!
The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0. Phase is a frequency domain or Fourier transform domain concept, and as such, can be readily understood in terms of simple harmonic motion. The same concept applies to wave motion, viewed either at a point in space over an interval of time or across an interval of space at a moment in time. Simple harmonic motion is a displacement that varies cyclically, as depicted to the right.It is described by the formula:where A is the amplitude of oscillation, f is the frequency, t is the elapsed time, and θ is the phase of the oscillation. The phase determines or is determined by the initial displacement at time t = 0. A motion with frequency f has period !!!!
The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe. The big bang theory is an effort to explain what happened during and after that moment.According to the standard theory, our universe sprang into existence as "singularity" around 13.7 billion years ago. What is a "singularity" and where does it come from? Well, to be honest, we don't know for sure. Singularities are zones which defy our current understanding of physics. They are thought to exist at the core of "black holes." Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density (a mathematical concept which truly boggles the mind). These zones of infinite density are called "singularities." Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense, something - a singularity. Where did it come from? We don't know. Why did it appear? We don't know.After its initial appearance, it apparently inflated (the "Big Bang"), expanded and cooled, going from very, very small and very, very hot, to the size and temperature of our current universe. It continues to expand and cool to this day and we are inside of it: incredible creatures living on a unique planet, circling a beautiful star clustered together with several hundred billion other stars in a galaxy soaring through the cosmos, all of which is inside of an expanding universe that began as an infinitesimal singularity which appeared out of nowhere for reasons unknown. This is the Big Bang theory !!!!!
Newton showed that, for spherical objects, you can make the simplifying assumption that all of the object's mass is concentrated at the center of the sphere. The following equation expresses the gravitational attraction that two spherical objects have on one another:
F = G * M1 * M2 / R2
R is the distance separating the two objects.
G is a constant that is 6.67259x10-11m3/s2 kg.
M1 and M2 are the two masses that are attracting each other.
F is the force of attraction between them.
Assume that Earth is one of the masses (M1) and a 1-kg sphere is the other (M2). The force between them is 9.8 kg*m/s2 -- we can calculate this force by dropping the 1-kg sphere and measuring the acceleration that the Earth's gravitational field applies to it (9.8 m/s2).
The radius of the Earth is 6,400,000 meters (6,999,125 yards). If you plug all of these values in and solve for M1, you find that the mass of the Earth is 6,000,000,000,000,000,000,000,000 kilograms (6E+24 kilograms / 1.3E+25 pounds) !!!!!
this should be "stereoscopic vision"
dat refers to the ability that humans have to see the same scene with
both eyes in slightly different ways. It results in our ability to visually
perceive depth and distances !!!!!
'Time Travel paradox' which goes something like this :Suppose a person travels to a time before she was born and breaks a causal chain that led to the traveler's birth. This problem has been commonly explored by asking 'What if you killed your own grandmother before she first conceived?' (Curiously the problem is never expressed in terms of killing your own mother). The apparent paradox is then of a logical sort: P entails NOT P and NOT P entails P. If you kill your grandmother then you would not be born, which in turn would bring it about that you not travel into the past, thus you would not kill your grandmother, thus you would be born causing you to again travel into the past to kill your grandmother !!!!!
Elasticity is the amount of stretch that an object contains. It is property by virtue of which matter keeps its shape from deforming into another.When an external force is applied to an object the size and shape of the object may change, for example, an appropriate force is applied to a spring can elongate it. If the force ceases to act the object may restore to its original size and shape. An object is said to be elastic if it restores its original size and shape. This property of an object is known as elasticity !!!!!
The multiverse (or meta-universe, metaverse) is the hypothetical set of multiple possible universes (including our universe) that together comprise everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. The term was coined in 1895 by the American philosopher and psychologist William James. The different universes within the multiverse are sometimes called parallel universes !!!!!
