Electrostatic fields come from a voltage gradient and can exist when charge carriers are stationary.
The potential gradient is in all cases lower in summer than winter, and thus the reduction in c 1 in summer would appear even larger than in Table V.
He found the gradient nearly uniform for heights up to 30 to 40 metres above the ground.
Sometimes, however, a sharp incline occurring on an otherwise easy line is not reckoned as the ruling gradient, trains heavier than could be drawn up it by a single engine being helped by an assistant or " bank " engine; sometimes also " momentum " or " velocity " grades, steeper than the ruling gradient, are permitted for short distances in cases where a train can approach at full speed and thus surmount them by the aid of its momentum.
Some of the earliest balloon observations made the gradient increase with the height, but such a result is now regarded as abnormal.
North of this line, near which the temperature is a little over 80° F., the gradient trends somewhat to the east of north, and the temperature is slightly higher on the western than on the eastern side until, in 4 5° N.
Dvina flows with a very slight gradient through a broad valley, and reaches the White Sea at Archangel.
The gradient or grade of a line is the rate at which it rises or falls, above or below the horizontal, and is expressed by stating either the horizontal distance in which the change of level amounts to r ft., or the amount of change that would occur in some selected distance, such as roo ft., r000 ft.
In America a gradient of r in roo is often known as a r% grade, one of 2 in roo as a 2% grade, and so on; thus a 0-25% grade corresponds to what in England would be known as a gradient of r in 400.
The ruling gradient of a section of railway is the steepest incline in that section, and is so called because it governs or rules the maximum load that can be placed behind an engine working over that portion of line.
In practice the gradient should not exceed i in 221, and even that is too steep, since theoretical conditions cannot always be realized; a wet rail will reduce the adhesion, and the gradients must be such that some paying load can be hauled in all weathers.
The pull recorded on the diagram includes the resistances due to acceleration and to the gradient on which the train is moving.
Thus a gradient of I in 200 is the same as a half per cent.
Hence if a train is travelling up the gradient at a speed of V ft.
Per hour up a gradient of I in 300, the extra horse-power required will be H.P. _280X2240X58.6 =22 300 X 550 3.
If the train is running down a gradient this horse-power is the rate at which gravity is working on the train, so that with the data of the previous section, on the assumption that the train is running down a gradient of I in 300, the horse-power required to maintain the speed would be 354-223=131.
17 at a speed corresponding to the average speed during the acceleration a, G the gradient, g the acceleration due to gravity, and V the velocity of the train in feet per second.
These considerations also indicate what a difficult matter it is to find the exact rate of working against the resistances, because of the difficulty of securing conditions which eliminate the effect both of the gradient and of acceleration.
First, it must be able to exert a tractive force sufficient to start the train under the worst conditions possible on the railway over which it is to operate - for instance, when the train is stopped by signal on a rising gradient where the track is curved and fitted with a guard-rail.
The two last curves in the diagram contrast the diurnal variation at Kew in potential gradient and in barometric pressure for the year as a whole.
In this table, unlike Table IV., amplitudes are all expressed as decimals of the mean value of the potential gradient for the corresponding season.
From observations during twelve balloon ascents, Linke concludes that below the 1500-metre level there are numerous sources of disturbance, the gradient at any given height varying much from day to day and hour to hour; but at greater heights there is much more uniformity.
At most stations a negative potential gradient is exceptional, unless during rain or thunder.
Will give a general idea of the relations of potential gradient to dissipation and ionization.
Table Potential, Dissipation, Ioniz If we regard the potential gradient near the ground as representing a negative charge on the earth, then if the source of supply of that charge is unaffected the gradient will rise and become high when the operations by which discharge is promoted slacken their activity.
South of this anticyclone, from about the latitude of the Cape, we find the region where, on account of the uninterrupted sea surface right round the globe, the planetary circulation is developed to the greatest extent known; the pressure gradient is steep, and the region is swept continuously by strong westerly winds - the " roaring forties."
Taking their origin from a series of lacustrine basins scattered over the plateaus and differing slightly in elevation, the Russian rivers describe immense curves before reaching the sea, and flow with a very gentle gradient, while numerous large tributaries collect their waters from over vast areas.
Brunel laid out the Great Western for a long distance out of London with a ruling gradient of i in 1320.
The Locher rack, employed on the Mount Pilatus railway, where the steepest gradient is nearly I in 2, is double, with vertical teeth on each side, while in the Strub rack, used on the Jungfrau line, the teeth are cut in the head of a rail of the ordinary Vignoles type.
The lines through them should be, if possible, straight and on the level; the British Board of Trade forbids them being placed on a gradient steeper than i in 260, unless it is unavoidable.
If W I is the weight of the train in pounds, the rate of working against the gradient expressed in horse-power units is H.P.=W,V/550 G.
The bridle road up the mountain leaves Glen Nevis at Achintee; it has a gradient nowhere exceeding 1 in 5, and the ascent is commonly effected in two to three hours.
At a distance from the central core the radiating ridges become less abrupt and descend with a gentle gradient, finally passing somewhat abruptly, at a height of some 7000 ft., into the level plateau.
Sometimes, as on the Central London railway, the acceleration of gravity is also utilized; the different stations stand, as it were, on the top of a hill, so that outgoing trains are aided at the start by having a slope to run down, while incoming ones are checked by the rising gradient they encounter.
9.5 in.); maximum gradient, I in 50; length of sleepers, 1.70 m.
Secondly, it must be able to maintain the train at a given speed against the total resistances of the level or up a gradient of given inclination.