Conduction sentence example
Here we have an instance of the conduction of heat.
His most important work was concerned with the conduction of heat and with spectroscopy.
This will be composed of a conduction and a convection current, the latter due to rising or falling air currents carrying ions.
This method of communication by magnetic induction through space establishes, therefore, a second method of wireless telegraphy which is quite independent of and different from that due to conduction through earth or water.
The special properties of these solutions are dealt with under Electrolysis and Electric conduction, § In Liquids.Advertisement
The mathematical theory of conduction of heat was developed early in the 19th century by Fourier and other workers, and was brought to so high a pitch of excellence that little has remained for later writers to add to this department of the subject.
The heat per second gained by conduction by an element dx of the bar, of conductivity k and cross section q, at a point where the gradient is dB/dx, may be written gk(d 2 6/dx 2)dx.
The fact that conduction occurred preponderantly in certain directions was explained by appeal to a hypothetical resistance to conduction which, for reasons unascertained, lay less in some directions than in others.
The phenomena attendant on the passage of electricity through solids, through liquids and through gases, are described in the article Electric conduction, and also Electrolysis, and the propagation of electrical vibrations in Electric Waves.
Preece, who took up the subject about the same time as Prof. Trowbridge, obtained improved practical results by combining together methods of induction and conduction.Advertisement
In all cases, while the internal threads which bear the cortical branches consist of elongated cells with few chromatophores, and no doubt serve mainly for conduction of food substances, the superficial cells of the branches themselves are packed with chromatophores and form the chief assimilating tissue of the plant.
In the stalk of the sporogonium there is a similar strand, which is of course not in direct connection with, but continues the conduction of water from, the strand of the gametophytic axis.
Among other subjects at which he subsequently worked were the absorption of gases in blood (1837-1845), the expansion of gases by heat (1841-1844), the vapour pressures of water and various solutions (1844-1854), thermo-electricity (1851), electrolysis (1856), induction of currents (1858-1861), conduction of heat in gases (1860), and polarization of heat (1866-1868).
That is to say, instead of using Boyle's law, which supposes that the pressure changes so exceedingly slowly that conduction keeps the temperature constant, we must use the adiabatic relation p = kpy, whence d p /d p = y k p Y 1= yp/p, and U = (yp/p) [Laplace's formula].
Graham showed that the diffusion was approximately proportional to the difference in concentration, and on these lines a theory of diffusion was founded on the lines of Fourier's treatment of the conduction of heat.Advertisement
In measuring conduction of heat in fluids, it is possible to some extent to eliminate the effects of molar convection or mixing, but it would not be possible to distinguish between diffusion, or internal radiation, and conduction.
Weber's hypothesis of electric atoms, capable of diffusing through metallic bodies and conductors of electricity, but capable of vibration only in non-conductors, it is possible that the ultimate mechanism of conduction may be reduced in all cases to that of diffusion in metallic bodies or internal radiation in dielectrics.
Both in muscle and in nerve this spread is termed conduction.
One of the earliest was devoted to electrical conduction in a thin plate, and especially in a circular one, and it also contained a theorem which enables the distribution of currents in a network of conductors to be ascertained.
This gives a convection current of 2.7 X108 electrostatic units, or about 1/27 of the conduction current.Advertisement
The process of electric conduction in metals consists in the movement of detached electrons, and many other phenomena, both electrical and thermal, can be more or less completely explained by their agency.
A group of bodies may, however, be yet discovered between alloys and electrolytes in which evidence may be found of some gradual change from wholly metallic to electrolytic conduction.
In fact, for a considerable period, the term " theory of heat " was practically synonymous with the mathematical treatment of a conduction.
This continuum was held to render possible conduction in all directions throughout the grey matter of the whole nervous system.
Although the cell body or perikaryon of the neuron, with its contained nucleus, is essential for the maintenance of the life of the cell branches, it has become recognized that the actual process and function of "conduction" in many neurons can, and does, go on without the cell body being directly concerned in the conduction.Advertisement
Another discussed conduction in curved sheets; a third the distribution of electricity in two influencing spheres; a fourth the deter mination of the constant on which depends the intensity of induced currents; while others were devoted to Ohm's law, the motion of electricity in submarine cables, induced magnetism, &c. In other papers, again, various miscellaneous topics were treated - the thermal conductivity of iron, crystalline reflection and refraction, certain propositions in the thermodynamics of solution and vaporization, &c. An important part of his work was contained in his Vorlesungen fiber mathematische Physik (1876), in which the principles of dynamics, as well as various special problems, were treated in a somewhat novel and original manner.
These subjects are discussed in the articles Density; Thermometry; Calorimetry; Diffusion; Conduction Of Heat; and Condensation Of Gases.
Beneath these layers are masses of salter water, through which a thermal wave of small amplitude is slowly propagated to the bottom by conduction.
This is in fair agreement with the computed temperature due to the sun's radiation upon a perpendicular absorbing surface when no temperature is lost through conduction to the interior.
Fourier for the propagation of heat; and if, in Fourier's solution of any problem of heat-conduction, we change the word "temperature" to "potential" and write "electric current" instead of "flux of heat," we have the solution of a corresponding problem of electric conduction.Advertisement
He also determined the effect of change of temperature distribution on the rate of generation of heat by the current; and on the external loss of heat by radiation, convection and conduction.
In Thomson's theory it is expressly assumed that the reversible thermal effects may be considered separately without reference to conduction.
It is assumed that a flow of heat Q, due to conduction, tends to carry with it a proportional electric current C = aQ.
It is difficult to see how this complication can be avoided, unless the first postulate is abandoned, and the heat-flow due to conduction is assumed to be independent of the thermoelectric phenomena.
It simplifies the theory, and gives a possible relation between the constants, but it does not appear to remove the complication above referred to, which seems to be inseparable from any conduction theory.Advertisement
Neglecting" conduction, all the expressions which he gives are equivalent to the equations of Thomson.
Taking conduction into account in the application of the second law of thermodynamics, he proposes to substitute the inequality, Td/dET - P
Others have considered conduction in a metal to be analogous to electrolytic conduction, and the observed effects to be due to " migration of the ions."
Thomson's calculations on the conduction of heat showed that at some time between twenty millions and four hundred millions, probably about one hundred millions, of years ago, the physical conditions of the earth must have been entirely different from those which now obtain.
Given a certain allowable heat transmission, the principal points to be considered in connexion with insulation are, first cost, durability, weight and space occupied, the two last named being specially important factors on board ship. No exact rules can be laid down, as the conditions vary so greatly; and though experiments have been made to determine the actual heat conduction of various materials per unit of surface, thickness and temperature difference, the experience of actual practice is at present the only accepted guide.Advertisement
Digoxin also acts indirectly by increasing parasympathetic activity via the vagus nerve, further slowing atrioventricular node conduction.
Material contact would allow conduction, thus eliminating the reflective insulation effect.
Recent technological advances have refined the ability of pacemakers to mimic physiological cardiac conduction.
H Understand how bonding in metals can be used to explain electrical conduction.
Asked how nerve conduction studies work at which point bell went thank goodness.Advertisement
This same extended network also supports proton conduction, a flow of positive electricity that occurs much faster than the diffusion of ions.
In order for the channel to respond to the appropriate ligand they have specific regulatory domains attached to the ion conduction pathway.
Local anesthetic agents may be administered intradermally or subcutaneously to block impulse conduction in local nerve fibers.
Who is a bone conduction hearing aid suitable for?
Measurements of such order are usually made by diffraction techniques, which detect the ionic cores and the spins of the conduction electrons.Advertisement
A typical example would be heat conduction through a bolted flange.
However, the term also covers nerve conduction studies - testing the electrical function of nerve conduction studies - testing the electrical function of nerves in the limbs.
Similar nerve conduction results Studies show a " mild background demyelinating neuropathy " .
These are effective in reducing phonon conduction, i.e. heat transfer by lattice vibrations.
He was subsequently continuously engaged in extending the applications of the doctrine of electrolytic conduction in relation not only to the problems of chemical action but also, on the supposition that in certain conditions the air conducts electrolytically, to the phenomena of atmospheric electricity.
Y p chimney and by conduction into the brickwork backing of the stove is considerable.
In ordinary cases conduction and convection suffice to dissipate the heat generated by the brake, but when a great deal of lowering has to be rapidly performed, or heavy loads have to be lowered to a great depth, special arrangements have to be provided.
The electromotive force of the coil is, however, great enough to create in these air gaps displacement currents which are of magnitude sufficient to be equivalent to the conduction current required to actuate a telephone.
The top and bottom rows of the xylem rays are often developed as irregularly-thickened radially-elongated tracheids which serve for the radial conduction of water, and communicate with the ordinary tracheids of the secondary xylem by large bordered pits.
This conclusion is supported also by the evidence supplied by the phenomena of electrolytic conduction (see Conduction, Electric, § Ii.).
If we eliminate the reverse electromotive forces of polarization at the two electrodes, the conduction of electricity through electrolytes is found to conform to Ohm's law; that is, once the polarization is overcome, the current is proportional to the electromotive force applied to the bulk of the liquid.
This conclusion is confirmed by the results of the direct visual determination of ionic velocities (see Conduction, Electric, § Ii.), which, in cases where the transport number remains constant, agree with the values calculated from those numbers.
Thomson has shown (see CONDUCTION, ELECTRIC, § III.) that the negative ions in certain cases of gaseous conduction are much more mobile than the corresponding positive ions, and possess a mass of about the one-thousandth part of that of a hydrogen atom.
Conductivity.-Conductivity, whether thermic or electric, is very differently developed in different metals; and, as an exact knowledge of these conductivities is of great importance, much attention has been given to their numerical determination (see Electric conduction; and Conduction Of Heat).
In ordinary reverberatory and other heating furnaces the burning fuel is without the mass, so that the vessel containing the charge, and other parts of the plant, are raised to a higher temperature than would otherwise be necessary, in order to compensate for losses by radiation, convection and conduction.
If heat passes " of itself " from a higher to a lower temperature by conduction, convection or radiation, the transfer cannot be reversed without an expenditure of work.
Here we have an instance of the conduction of heat.'
That, however, complete conduction should arrive with alternations only ten times slower than light was an unexpected and remarkable fact, which verifies the presumption that the process of conduction is one in which the dynamic activities of the molecules do not come into play.
In the case of electrolytes we can go further, and calculate the diffusion constant itself from the theory of electrolytic dissociation (see Electric conduction, § In Liquids).
The heat generated by the current C at a point x where the temperature-excess is 0 is equal per unit length and time (t) to that lost by conduction -d(gkdo/dx)/dx, and by radiation hpo (emissivity h, perimeter p), together with that employed in raising the temperature gcdo/dt, and absorbed by the Thomson effect sCdo/dx.
At higher pressures the effect of conduction was masked by convection currents.
A continuous flow calorimeter has been used by the writer for measuring quantities of heat conveyed by conduction (see Conduction Of Heat), and also for determining the variation of the specific heat of water.
Thermal Hydraulics & Nuclear Engineering (25 lectures) Heat transfer by conduction, application to fuel elements.
Consider breakability, how likely it is to scratch while you cook, reactivity, and heat conduction.
Stainless steel is better than aluminum in some respects, but heat conduction isn't one of them.
One way around the heat conduction issue is to choose a pot or pan with an aluminum layer between two layers of stainless steel, either just on the bottom or all the way up the sides.
If this doesn't sway you, you'll reap the benefits of great heat conduction and a low price.
For passive design, this involves the natural methods of conduction, convention and radiation, which you may recall from science class.
Specialized testing of the nerves, called nerve conduction testing (NCV), can be performed to determine if CMT1 or CMT2 is present.
A nerve conduction velocity test should be performed to measure how fast impulses travel through the nerves.
Nerve conduction testing may be combined with electromyography (EMG), an electrical test of the muscles.
Nerve conduction studies and an electromyogram (EMG) are usually performed together to provide a comprehensive assessment of nerve and muscle function.
In the nerve conduction study, small electrodes are placed on the skin over the muscles to be examined.
The scar tissue puts pressure on the nerve and interferes with nerve signal conduction to the muscles.
It uses state-of-the-art technology that combines three cooking methods - the conventional oven element (conduction), convection cooking and infrared cooking.
If the battery leaks inside and dries, you'll have to clean out the grey gunk to be assured of clean conduction.
Telephonic speech between these two circuits was found possible and good, the communication between the circuits taking place partly by induction, and no doubt partly by conduction.
P. Granville put into practice between Alum Bay in the Isle of Wight and the Needles lighthouse a method which depends upon conduction through sea water.
The tissue developed to meet the demands for conduction in such cases always shows some of the characters described.
The internal tissue of the body of the solid higher Fungi, particularly the elongated stalks (stipes) of the fructifications of the Agarics, consists of hyphae running in a longitudinal direction, which no doubt serve for the conduction of organic food substances, just as do the trumpet-hyphae, similar in appearance, though not in origin, of the higher Brown Seaweeds.
The evidence in favour of dissociation in the case of solutions does not apply to fused salts, and it is possible that, in their case, a series of molecular interchanges, somewhat like Grotthus's chain, may represent the mechanism of conduction.
Our views of the nature of the ions of electrolytes have been extended by the application of the ideas of the relations between matter and electricity obtained by the study of electric conduction through gases.
It is, however, probable that conduction is to some extent a factor in the process.
Conduction, however, is generally understood to include diffusion of heat in fluids due to the agitation of the ultimate molecules, which is really molecular convection.
This agreement was a very satisfactory test of the accuracy of the fundamental law of conduction, as the gradients and periods varied so widely in the two cases.
The synapse appears to be a weak spot in the chain of conduction, or rather to be a place which breaks down with comparative ease under stress, e.g.
Heartbeat abnormalities such as tachycardia (rapid heart rate) and heart block (impaired conduction of the heart's cardiac impulses) are common occurrences.
Laboratory tests include electromyography (a measurement of the electrical activity of muscle cells) and nerve conduction velocity tests, which measure the speed that nerves transmit impulses.
Nerve conduction velocity tests, electromyography, and imaging studies of the affected area may be employed.
Both air conduction and bone conduction of sounds are evaluated by audiometry.
Air conduction establishes the extent of sound transmission through the bones of the middle ear.
The results of a bone conduction test determine how soft a sound an individual can hear over several frequencies or pitches.
Bone conduction audiometry determines the extent to which there is neurosensory hearing loss.
Since those with hearing losses often cannot hear sounds at normal decibel levels, intensities as high as 115 dB are used to assess the extent of air conduction loss and as high as 70 dB for bone conduction loss.
The difference between bone conduction loss and neurosensory hearing loss is called the air-bone gap.
The patient wears headphones when air conduction is tested and a vibrating earpiece behind the ear next to the mastoid bone or along the forehead when bone conduction is tested.
The clinician usually uses a special instrument called a tuning fork and tests for air conduction and structural problems which can occur inside the ear.
In some cases, nerve conduction studies with electromyography of the affected muscles may be performed to evaluate an underlying neuromuscular disorder.
A water-soluble gel is placed on the underside of the transducer to permit the conduction of fetal heart sounds.
In some cases, nerve conduction studies with electromyography of the affected muscles may be performed to evaluate the child's muscular activity and provide a comprehensive assessment of nerve and muscle function.
Inside the battery, the paste is wet and used for conduction.
Wood thus altered is known as heart-wood, or duramen, as distinguished from the young sap-wood, or alburnum, which, forming a cylinder next the cambium, remains alive and carries on the active functions of the xylem, particularly the conduction of water.
The object of all heating apparatus is the transference of heat from the fire to the various parts of the building it is intended to warm, and this transfer may be effected by radiation, by conduction or by convection.
Up to 1895 or 1896 the suggestions for wireless telegraphy which had been publicly announced or tried can thus be classified under three or four divisions, based respectively upon electrical conduction through the soil or sea, magnetic induction through space, combinations of the two foregoing, and lastly, electrostatic induction.
The presence of these threads between all the cells of tfie plant shows that the plant body must be regarded as a connected whole; the threads themselves probably play an important part in the growth of the cell-wall, the conduction of food and water, the process of secretion and the transmission of impulses.
The details of the calculation are given in the article Electric conduction, § where also will be found an account of the methods which have been used to measure the velocities of many ions by direct visual observation.
Some of the more important papers on the subject have been reprinted for Harper's Series of Scientific Memoirs in Electrolytic Conduction (1899) and the Modern Theory of Solution (1899).
In starting the furnace, the bottom is prepared by ramming it with charcoal-powder that has been soaked in milk of lime and dried, so that each particle is coated with a film of lime, which serves to reduce the loss of current by conduction through the lining when the furnace becomes hot.
The conduction through the amputated cell branches continues unimpaired for many hours.
The surface of the calorimeter and the enclosure should be permanently blackened so as to increase the loss of heat by radiation as much as possible, as compared with the losses by convection and conduction, which are less regular.
The method of induction between insulated primary and secondary circuits laid out flat on the surface of the earth proves to be of limited application, and in his later experiments Preece returned to a method which unites both conduction and induction as the means of affecting one circuit by a current in another.
Besides absorption, assimilation, conduction and protection there is another very important function for which provision has to be made in any plant-body of considerable size, especially when raised into the air, that of support.
These bundle sheaths are important in the conduction of carbohydrates away from the assimilating cells to other parts of the plant.
While it seems clear that the conduction in this case is carried on by ions similar to those of solutions, since Faraday's laws apply equally to both, it does not follow necessarily that semi-permanent dissociation is the only way to explain the phenomena.
Towards the end of his life he was occupied with experimental inquiries into the laws of the conduction of heat in bars, and his last piece of work was to show that the thermal conductivity of iron diminishes with increase of temperature.
He developed a great research laboratory of experimental physics, attracting numerous workers from many countries and colonies; advances were made in the investigation of the conduction of electricity through gases, in the determination of the charge and mass of the electron and in the development of analysis by means of positive rays.
Wilson considers that convection currents in the upper atmosphere would be quite inadequate, but conduction may, he thinks, be sufficient alone.
Dust particles interfere with conduction near the ground, so the relative conductivity in the upper layers may be much greater than that calculated.
Taking into account the heat absorbed by the box and the metal, Rumford calculated that the heat developed was sufficient to raise 26.58 lb of water from the freezing to the boiling point, and in this calculation the heat lost by radiation and conduction was neglected.
He also repeated the suggestion which Lindsay had already made that it might be possible to signal in this manner by conduction currents through the Atlantic Ocean from the United States to Europe.
On the view of the process of conduction described above, the amount of electricity conveyed per second is measured by the product of the number of ions, known from the concentration of the solution, the charge carried by each of them, and the velocity with which, on the average, they move through the liquid.
If heat passes "of itself" from a higher to a lower temperature by conduction, convection or radiation, the transfer cannot be reversed without an expenditure of work.
In this manner Trowbridge showed that signalling might be carried on over considerable distances by electric conduction through the earth or water between places not metallically connected.
On the question of how far the effects are due to conduction between the earth plates, and how far to true electromagnetic induction, authorities differ, some being of opinion that the two effects are in operation together.
Simple pits (p.) enable conduction to take place readily from one to another.
They are accompanied by intercellular channels serving for the conduction of oxygen to, and carbon dioxide from, the living cells in the interior of the wood, which would otherwise be cut off from the means of respiration.
Following on this he made an interesting experiment, using Morse's method, to connect the Isle of Wight telegraphically with the mainland, by conduction across the Solent in two places, during a temporary failure of the submarine cable in 1882 in that channel.
The increasing development of the wood as the tree grows older is largely due to the demands for the conduction of water and mineral matters dissolved in it, which are made by the increased number of leaves which from year to year it bears, and which must each be put into communication with the central mass by the formation of new vascular bundles.
The conduction of such stimulation to parts removed some distance from the sense organ suggests paths of transmission comparable to those which transmit nervous impulses in animals.
Kohlrausch formulated a theory of electrolytic conduction based on the idea that, under the action of the electric forces, the oppositely charged ions moved in opposite directions through the liquid, carrying their charges with them.
Liquid metal coming in contact with such a surface forms a crust of solidified metal over it, and this crust thickens up to a certain point, namely, until the heat from within the furnace just overbalances that lost by conduction through the solidified crust and the cathode material to the flowing water.
Wilson supposes that by the fall to the ground of a preponderance of negatively charged rain the air above the shower has a higher positive potential than elsewhere at the same level, thus leading to large conduction currents laterally in the highly conducting upper layers.
The interpretation of the phenomena of gaseous conduction was rendered possible by the knowledge previously acquired of conduction through liquids; the newer subject is now reaching a position whence it can repay its debt to the older.
He held his prefecture for fourteen years; and it was during this period that he carried on his elaborate and fruitful investigations on the conduction of heat.
When a liquid undergoing evaporation is contained in a closed vessel, a molecule which has left the liquid will, after a certain 1 Other processes also help in the conduction of heat, especially in substances which are conductors of electricity.