72 Sentences With "equipotential" | Random Sentence Generator

Or if you like technical terms, below the common equipotential surface.

You can see that moving parallel to these conducting plates is mostly moving along an equipotential line.

The first study provides the most detailed topographical map of Titan to date, while the second study piggybacks off this research, showing that Titan's largest seas and lakes have a common equipotential surface, meaning they form a common sea level.

The del operator illustrates the relationship between a vector field and its associated scalar potential field. An equipotential region might be referred as being 'of equipotential' or simply be called 'an equipotential'. An equipotential region of a scalar potential in three-dimensional space is often an equipotential surface, but it can also be a three-dimensional region in space. The gradient of the scalar potential (and hence also its opposite, as in the case of a vector field with an associated potential field) is everywhere perpendicular to the equipotential surface, and zero inside a three-dimensional equipotential region.

Gravity is perpendicular to the equipotential surfaces of the gravity potential, and in electrostatics and in the case of steady currents the electric field (and hence the electric current, if any) is perpendicular to the equipotential surfaces of the electric potential (voltage). In gravity, a hollow sphere has a three-dimensional equipotential region inside, with no gravity (see shell theorem). In electrostatics a conductor is a three- dimensional equipotential region. In the case of a hollow conductor (Faraday cage), the equipotential region includes the space inside.

An isopotential map is a measure of electrostatic potential in space, often depicted in two dimensions with the electrostatic charges inducing that electric potential. The term equipotential line or isopotential line refers to a curve of constant electric potential. Whether crossing an equipotential line represents ascending or descending the potential is inferred from the labels on the charges. In three dimensions, equipotential surfaces may be depicted with a two dimensional cross-section, showing equipotential lines at the intersection of the surfaces and the cross-section.

Computed electrostatic equipotentials (black contours) between two electrically charged spheres Equipotential or isopotential in mathematics and physics refers to a region in space where every point in it is at the same potential.Weisstein, Eric W. "Equipotential Curve." Wolfram MathWorld. Wolfram Research, Inc.

Georgia State University, n.d. Web. 22 Aug 2011.Schmidt, Arthur G. "Equipotential Lines." Northwestern University.

A common envelope is sometimes confused with a contact binary. In a common envelope binary system the envelope does not generally rotate at the same rate as the embedded binary system; thus it is not constrained by the equipotential surface passing through the L2 Lagrangian point. In a contact binary system the shared envelope rotates with the binary system and fills an equipotential surface.

A ball will not be accelerated left or right by the force of gravity if it is resting on a flat, horizontal surface, because it is an equipotential surface.

Equipotential bonding involves electrically connecting metalwork so that it is at the same voltage everywhere. Exact rules for electrical installations vary by country, locality, or supplying power company. Equipotential bonding is done from where the distribution wiring enters the building to incoming water and gas services. It is also done in bathrooms where all exposed metal that leaves the bathroom including metal pipes and the earths of electrical circuits must be bonded together to ensure that they are always at the same potential.

An engineering analysis of the power system under fault conditions can be used to determine whether or not hazardous step and touch voltages will develop. The result of this analysis can show the need for protective measures and can guide the selection of appropriate precautions. Several methods may be used to protect employees from hazardous ground-potential gradients, including equipotential zones, insulating equipment, and restricted work areas. The creation of an equipotential zone will protect a worker standing within it from hazardous step and touch voltages.

Equipotential lines are shown here, which can be compared with the contour lines on a map of a mountainous region: the nearer these lines are to each other, the steeper the slope and the greater the danger, in this case the danger of an electrical breakdown. The equipotential lines can also be compared with the isobars on a weather map: The denser the lines, the more wind and the greater the danger of damage. In order to control the equipotential lines (that is to control the electric field) a device is used that is called a stress cone, see figure 3.Kreuger 1991 Vol. 1, pp. 147-153 The crux of stress relief is to flare the shield end along a logarithmic curve. Before 1960, the stress cones were handmade using tape—after the cable was installed.

2nd Nat. Dairy Housing Conf., 1983 of stray voltage in the farm environment. Today, stray voltage on farms is regulated by state governments and controlled by the design of equipotential planes in areas where livestock eat, drink or give milk.

For geophysical applications, gravity is distinguished from gravitation. Gravity is defined as the resultant of gravitation and the centrifugal force caused by the Earth's rotation. The global mean sea surface is close to one of the equipotential surfaces of the geopotential of gravity W. This equipotential surface, or surface of constant geopotential, is called the geoid.. How the gravitational force and the centrifugal force add up to a force orthogonal to the geoid is illustrated in the figure (not to scale). At latitude 50 deg the off-set between the gravitational force (red line in the figure) and the local vertical (green line in the figure) is in fact 0.098 deg.

The formulas for calculating the normal gravity is based on the assumption of an imagined rotationally symmetrical ellipsoid model of the earth, the surface of which is identical to an equipotential surface. Consequently this formula depends only on the geographical latitude and the elevation of geographical location.

Map of countries coloured according to their highest point The following sortable table lists land surface elevation extremes by country or dependent territory. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface.

The collector is shaped to provide a smooth equipotential surface underneath the corona wire. Variations of this include a wire mesh, parallel conductive tubes, or a foil skirt with a smooth, round edge. Sharp edges on the skirt degrade performance, as it generates ions of opposite polarity to those within the thrust mechanism.

Northwestern University, n.d. Web. 22 Aug 2011. This usually refers to a scalar potential (in that case it is a level set of the potential), although it can also be applied to vector potentials. An equipotential of a scalar potential function in n-dimensional space is typically an (n−1)dimensional space.

Cedergren, Harry R. (1977), Seepage, Drainage, and Flow Nets, Wiley. One set of lines in the flownet are in the direction of the water flow (flow lines), and the other set of lines are in the direction of constant total head (equipotential lines). Flownets may be used to estimate the quantity of seepage under dams and sheet piling.

Geoid Glacier () is a glacier flowing south from the Thomas Heights, to the west of Ellipsoid Hill, into Blue Glacier, Victoria Land, Antarctica. The name is one of a group in the area associated with surveying applied in 1993 by the New Zealand Geographic Board, the geoid being the particular equipotential surface which coincides with mean sea level.

Hermann was born in Berlin. In addition to his work in phonetics, he was influential as a physiologist. He opposed the notion, propounded by Emil du Bois-Reymond, that muscles contained an ordered series of "electromotive molecules" in favor of a theory of chemical activity. Hermann showed that the entire surface of an uninjured muscle was electrically equipotential.

The top flow line of a saturated soil mass below which seepage takes place, is called the Phreatic line. Hydrostatic pressure acts below the phreatic line whereas atmospheric pressure exists above the phreatic line. This line separates a saturated soil mass from an unsaturated soil mass. It is not an equipotential line, but a flow line.

Note that the above equation describes the Earth's gravitational potential V\ , not the geoid itself, at location \phi,\;\lambda,\;r,\ the co-ordinate r\ being the geocentric radius, i.e., distance from the Earth's centre. The geoid is a particular equipotential surface, and is somewhat involved to compute. The gradient of this potential also provides a model of the gravitational acceleration.

Data from GRACE has improved the current Earth gravitational field model, leading to improvements in the field of geodesy. This improved model has allowed for corrections in the equipotential surface which land elevations are referenced from. This more accurate reference surface allows for more accurate coordinates of latitude and longitude and for less error in the calculation of geodetic satellite orbits.

Modeling the topography of the salar de Uyuni, Bolivia, as an equipotential surface of Earth's gravity field. Journal of Geophysical Research: Solid Earth, 113(B10). As a result, the variation in the surface elevation over the area of Salar de Uyuni is less than normal to the Earth's circumference, and there are few square kilometers on Earth that are as flat.

Figure 8, the earth shield of a cable (0%) is cut off, the equipotential lines (from 20% to 80%) concentrate at the edge of the earth electrode, causing danger of breakdown. alt= Terminals of high-voltage cables must manage the electric fields at the ends.Kreuger 1991 Vol. 1, pp. 53,147,153 Without such a construction the electric field will concentrate at the end of the earth-conductor as shown in figure 2.

Until the 1950s, isolated ground domestic mains supplies tended to have no Residual-Current Device (RCD) or Earth Leakage Circuit Breaker (ELCB), and too high a ground impedance to blow a fuse if a live-to-earth fault occurred. This could leave metalwork in the house live. The use of Residual Current Devices (RCDs) or formerly ELCBs with such installs solved this problem. Such installs are called EEBAD (Earthed Equipotential Bonding and Automatic Disconnection).

No mention is provided of either the necessary space-charge or equipotential distribution, and these remain to be specified for the notion of acceleration by double layers to be credible. Fundamentally, Poisson's equation indicates that there can be no configuration of charge resulting in a net potential drop. Inexplicably though, some authorsBoström, Rolf "Observations of weak double layers on auroral field lines" (1992) IEEE Transactions on Plasma Science (), vol. 20, no. 6, pp.

Such a zone can be produced through the use of a metal mat connected to the grounded object. Usually this metal mat (or ground mesh) is connected to buried ground rods to increase contact with the earth and effectively reduce grid impedance. In some cases, a grounding grid can be used to equalize the voltage within the grid. Equipotential zones will not, however, protect employees who are either wholly or partially outside the protected area.

A flownet is a graphical representation of two-dimensional steady-state groundwater flow through aquifers. Construction of a flownet is often used for solving groundwater flow problems where the geometry makes analytical solutions impractical. The method is often used in civil engineering, hydrogeology or soil mechanics as a first check for problems of flow under hydraulic structures like dams or sheet pile walls. As such, a grid obtained by drawing a series of equipotential lines is called a flownet.

Electrical conductors offer an intuitive example. If a and b are any two points within or at the surface of a given conductor, and given there is no flow of charge being exchanged between the two points, then the potential difference is zero between the two points. Thus, an equipotential would contain both points a and b as they have the same potential. Extending this definition, an isopotential is the locus of all points that are of the same potential.

In the ESD protected area, all conductors in the environment, including personnel, shall be bonded or electrically connected and attached to a known ground or contrived ground. This attachment creates an equipotential balance between all items and personnel. Electrostatic protection can be maintained at a potential above a "zero" voltage ground potential as long as all items in the system are at the same potential. Antistatic garments are used in many industries such as electronics, communications, telecommunications and defense applications.

Mount Elbert in the Sawatch Range is the highest peak of the Rocky Mountains and the highest point in Colorado. The following sortable table comprises the 100 most topographically prominent mountain peaks of the U.S. State of Colorado. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit.

This is an important measure for electric shock protection. When this protective function is the purpose of bonding, BS 7671 describes the bonding by the term "protective equipotential bonding"; this does not mean that the bonding guarantees perfect equipotentiality, but just that it reduces the differences of potential. In the following, this formal term is abbreviated to "bonding". Without adequate bonding, dangerous voltages could arise between conductive parts that can be touched simultaneously, either due to problems outside the installation, or to faults in the installation.

Denali in Alaska is the highest mountain peak of the United States and North America. Denali is the third most topographically prominent and third most topographically isolated summit on Earth after Mount Everest and Aconcagua. The following sortable table comprises the 23 mountain peaks of the U.S. State of Alaska with at least of topographic elevation and at least of topographic prominence. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface.

In 1919, the renowned physicist, Albert A. Michelson, noted that the most favorable arrangement to obtain high sensitivity and immunity from temperature perturbations is to use the equipotential surface defined by water in a buried half-filled water pipe. This was a simple arrangement of two water pots, connected by a long water- filled tube. Any change in tilt would be registered by a difference in fill- mark of one pot compared to the other. Although extensively used throughout the world for earth-science research, they have proven to be quite difficult to operate.

It may also be applied to other situations where a continuous medium has smoothly varying density, such as in the case of an inhomogeneous colloidal suspension. In general isopycnic surfaces will occur in fluids in hydrostatic equilibrium coinciding with equipotential surfaces formed by gravity. The term "isopycnic" is also encountered in biophysical chemistry, usually in reference to a process of separating particles, subcellular organelles, or other substances on the basis of their density. Isopycnic centrifugation refers to a method wherein a density gradient is either pre-formed or forms during high speed centrifugation.

Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit. The topographic isolation of a summit is the minimum great-circle distance to a point of equal elevation. This article defines a significant summit as a summit with at least of topographic prominence, and a major summit as a summit with at least of topographic prominence.

When the limb buds were transplanted in halves or doubled, they still developed into normal limbs. Harrison concluded that the information from the host (the surrounding embryo cells) directed the cells to develop normally even though they were transplanted in halves or doubles. Therefore, the limb buds were all equipotential, meaning they all developed the same way, and the tissue around the limb buds determined their dorsoventral orientation. However, when a left limb was put on the right side of the body, a left limb grew anyway despite its relocation.

The average diameter of the reference spheroid is . Local topography deviates from this idealized spheroid, although on a global scale these deviations are small compared to Earth's radius: the maximum deviation of only 0.17% is at the Mariana Trench ( below local sea level), whereas Mount Everest ( above local sea level) represents a deviation of 0.14%. In geodesy, the exact shape that Earth's oceans would adopt in the absence of land and perturbations such as tides and winds is called the geoid. More precisely, the geoid is the surface of gravitational equipotential at mean sea level.

Aside from its use in the production of CRTs, Aquadag is used in many types of high-voltage lab apparatus where a conductive coating is needed on an insulating surface. The surfaces of some metals (most notably aluminum) can develop nonconductive oxide layers, which tend to disrupt the electrostatic field produced around the surface of the metal when used as an electrode. Aquadag is not subject to such effects and provides a completely uniform equipotential surface for electrostatics. Producers of continuous filament fiberglass will coat their product with Agadag when a conductive property is required.

Mount Whitney is the highest summit of the Sierra Nevada, the State of California, and the contiguous United States. The following sortable table describes the 46 mountain peaks of the U.S. state of California with at least of topographic elevation and at least of topographic prominence. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit.

An enlargeable satellite photograph of the portion of the Rocky Mountains within the State of Colorado The following table lists the major mountain ranges of the U.S. State of Colorado. All of these ranges can be considered subranges of the Rocky Mountains. As given in the table, topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit.

Mount Whitney is the highest summit of the Sierra Nevada, the State of California, and the contiguous United States. The following sortable table comprises the 16 mountain peaks of the U.S. State of California with at least of topographic elevation and at least of topographic prominence. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit.

The ceiling can therefore be conceived as an ice shelf that is grounded along its entire perimeter, which explains why it has been called a captured ice shelf. As it moves over the lake, it enters the lake at the floating line, and it leaves the lake at the grounding line. A hydrostatic seal is created when the ice is so much higher around the lake that the equipotential surface dips down into impermeable ground. Water from underneath this ice rim is then pressed back into the lake by the hydrostatic seal.

Mean sea level was measured at 26 tide gauges: 21 in the United States and 5 in Canada. The datum was defined by the observed heights of mean sea level at the 26 tide gauges and by the set of elevations of all bench marks resulting from the adjustment of observations. The adjustment required a total of 66,315 miles (106,724 km) of levelling with 246 closed circuits and 25 circuits at sea level. Since the Sea Level Datum of 1929 was a hybrid model, it was not a pure model of mean sea level, the geoid, or any other equipotential surface.

A multipoint ground is an alternate type of electrical installation that attempts to solve the ground loop and mains hum problem by creating many alternate paths for electrical energy to find its way back to ground. The distinguishing characteristic of a multipoint ground is the use of many interconnected grounding conductors into a loose grid configuration. There will be many paths between any two points in a multipoint grounding system, rather than the single path found in a star topology ground. This type of ground may also be known as a Signal Reference Grid or Ground (SRG) or an Equipotential Ground.

Mount Elbert in the Sawatch Range is the highest peak of the Rocky Mountains and the highest point in the U.S. state of Colorado. The following sortable table comprises the 117 highest mountain peaks of the U.S. State of Colorado with at least of elevation and at least of topographic prominence. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The topographic prominence of a summit is the elevation difference between that summit and the highest or key col to a higher summit.

So for all intents and purposes, the Faraday shield generates the same static electric field on the outside that it would generate if the metal were simply charged with +Q. See Faraday's ice pail experiment, for example, for more details on electric field lines and the decoupling of the outside from the inside. Note that electromagnetic waves are not static charges. If the cage is grounded, the excess charges will be neutralized as the ground connection creates an equipotential bonding between the outside of the cage and the environment, so there is no voltage between them and therefore also no field.

Figure 4: The Moon's gravity differential field at the surface of the Earth is known (along with another and weaker differential effect due to the Sun) as the Tide Generating Force. This is the primary mechanism driving tidal action, explaining two tidal equipotential bulges, and accounting for two high tides per day. In this figure, the Earth is the central blue circle while the Moon is far off to the right. The outward direction of the arrows on the right and left indicates that where the Moon is overhead (or at the nadir) its perturbing force opposes that between the earth and ocean.

The currently most widely used reference ellipsoid, that of the Geodetic Reference System 1980 (GRS80), approximates the geoid to within a little over ±100 m. One can construct a simple model geopotential U that has as one of its equipotential surfaces this reference ellipsoid, with the same model potential U_0 as the true potential W_0 of the geoid; this model is called a normal potential. The difference T=W-U is called the disturbing potential. Many observable quantities of the gravity field, such as gravity anomalies and deflections of the plumbline, can be expressed in this disturbing potential.

The usefulness of the stream function lies in the fact that the flow velocity components in the x- and y- directions at a given point are given by the partial derivatives of the stream function at that point. A stream function may be defined for any flow of dimensions greater than or equal to two, however the two-dimensional case is generally the easiest to visualize and derive. For two-dimensional potential flow, streamlines are perpendicular to equipotential lines. Taken together with the velocity potential, the stream function may be used to derive a complex potential.

This is due to the limited finite conductivity of the layers of soil in the earth. The gradient of the voltage (changing voltage within a distance) may be so high that two points on the ground may be at significantly different potentials, creating a hazard to anyone standing on the ground in the area. Pipes, rails, or communication wires entering a substation may see different ground potentials inside and outside the substation, creating a dangerous touch voltage. This problem is alleviated by creating a low-impedance equipotential bonding plane within the substation installed in accordance with IEEE 80.

In a building with electricity it is normal for safety reasons to connect all metal objects such as pipes together to the mains earth to form an equipotential zone. This is done in the UK because many buildings are supplied with a single phase supply cable where the neutral and earth conductors are combined. Close to the electricity meter this conductor is divided into two, the earth terminal and the wire going to the neutral busbar in the consumer unit. If the ground connection to the neutral is lost, all wiring and other objects tied to the neutral will be energized at the line voltage.

The capacitance of nanoscale dielectric capacitors such as quantum dots may differ from conventional formulations of larger capacitors. In particular, the electrostatic potential difference experienced by electrons in conventional capacitors is spatially well-defined and fixed by the shape and size of metallic electrodes in addition to the statistically large number of electrons present in conventional capacitors. In nanoscale capacitors, however, the electrostatic potentials experienced by electrons are determined by the number and locations of all electrons that contribute to the electronic properties of the device. In such devices, the number of electrons may be very small, so the resulting spatial distribution of equipotential surfaces within the device are exceedingly complex.

The geoid, or mathematical mean sea surface, is defined not only on the seas, but also under land; it is the equilibrium water surface that would result, would sea water be allowed to move freely (e.g., through tunnels) under the land. Technically, an equipotential surface of the true geopotential, chosen to coincide (on average) with mean sea level. As mean sea level is physically realized by tide gauge bench marks on the coasts of different countries and continents, a number of slightly incompatible "near- geoids" will result, with differences of several decimetres to over one metre between them, due to the dynamic sea surface topography.

10.7 On this rubber-like body R a shield electrode is applied that spreads the equipotential lines to guarantee a low electric field. The crux of this device, invented by NKF in Delft in 1964,Dutch Patent 123795, Netherlands Cable Works NKF, submitted 21-4-1964, granted 27-3-1968 is that the bore of the elastic body is narrower than the diameter of the cable. In this way the (blue) interface between cable and stress-cone is brought under mechanical pressure, so that no cavities or air pockets can be formed between cable and cone. Electric breakdown in this region is prevented in this way.

This article defines greater North America as the portion of the continental landmass of the Americas extending westward and northward from the Isthmus of Panama plus the islands surrounding that landmass. This article defines the islands of North America to include the coastal islands of North America, the islands of the Caribbean Sea, the Lucayan Archipelago, the Bermuda Islands, the Islands of Greenland (Kalaallit Nunaat), the islands of Northern Canada, the islands of Alaska, and the islands of the northeastern Pacific Ocean. The Hawaiian Islands are not included because they are considered part of Oceania. Topographic elevation is the vertical distance above the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface.

Resistance paper,"The outline (or boundaries)of the trough are drawn on the resistance paper with silver (conducting) paint. ... Another field-mapping arrangement using resistance paper is shown ...a pantograph for transferring equipotential points from the resistance paper to ...resistance-paper analog." "...commonly used laboratory setups are the uniform resistance paper, such as Teledeltos paper, ..." also known as conductive paper and by the trade name Teledeltos paper is paper impregnated or coated with a conductive substance such that the paper exhibits a uniform and known surface resistivity. Resistance paper and conductive ink were commonly used as an analog two- dimensional"Resistance paper is very simple to use for two-dimensional problems..." electromagnetic field solver.

In special circumstances (not domestic installations) bonding with deliberate lack of connection to earth (earth free local equipotential bonding) may be used. Bonding, by the IEC 60364 terminology used in BS 7671, should not be seen as just an extra to earthing. In recent US practice, which differs considerably from IEC principles and terminology, "bonding" is used more widely as a term for all the aspects of earthing that are not literally connections with the earth itself ("grounding"); so the connection of protective earth conductors to the supply neutral (since the TN-C-S system is the only permitted form in their residential installations) is now named bonding rather than earthing. This is not the case in the UK.

The desire to power electronic equipment using AC mains power faced a difficulty with respect to the powering of the tubes' filaments, as these were also the cathode of each tube. Powering the filaments directly from a power transformer introduced mains-frequency (50 or 60 Hz) hum into audio stages. The invention of the "equipotential cathode" reduced this problem, with the filaments being powered by a balanced AC power transformer winding having a grounded center tap. A superior solution, and one which allowed each cathode to "float" at a different voltage, was that of the indirectly heated cathode: a cylinder of oxide-coated nickel acted as an electron-emitting cathode and was electrically isolated from the filament inside it.

The outer one is at earth potential and spreads the electric field in a similar way as in a cable terminal. The inner one is at high-voltage and shields the connector of the conductors from the electric field. The field itself is diverted as shown in figure 8, where the equipotential lines are smoothly directed from the inside of the cable to the outer part of the bi-manchet (and vice versa at the other side of the device).none none The crux of the matter is here, like in the cable terminal, that the inner bore of this bi-manchet is chosen smaller than the diameter over the cable insulation.

In his original 1905 paper on special relativity, Albert Einstein suggested a possible test of the theory: "Thence we conclude that a spring-clock at the equator must go more slowly, by a very small amount, than a precisely similar clock situated at one of the poles under otherwise identical conditions." Actually, it is now known that all clocks located at sea level on the Earth's surface tick at the same rate, regardless of latitude, because kinematic and gravitational time dilation effects cancel out (assuming that Earth's surface is an equipotential one). The kinematic effect was verified in the 1938 Ives–Stilwell experiment and in the 1940 Rossi–Hall experiment. General relativity's prediction of the gravitational effect was confirmed in 1959 by Pound and Rebka.

The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vertical datum). The term elevation is mainly used when referring to points on the Earth's surface, while altitude or geopotential height is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and depth is used for points below the surface. Elevation is not to be confused with the distance from the center of the Earth. Due to the equatorial bulge, the summits of Mount Everest and Chimborazo have, respectively, the largest elevation and the largest geocentric distance.

But as residual current devices mitigate this disadvantage, the TT earthing system has become much more attractive providing that all AC power circuits are RCD-protected. In some countries (such as the UK) TT is recommended for situations where a low impedance equipotential zone is impractical to maintain by bonding, where there is significant outdoor wiring, such as supplies to mobile homes and some agricultural settings, or where a high fault current could pose other dangers, such as at fuel depots or marinas. The TT earthing system is used throughout Japan, with RCD units in most industrial settings. This can impose added requirements on variable frequency drives and switched-mode power supplies which often have substantial filters passing high frequency noise to the ground conductor.

The ellipsoid is a mathematically defined regular surface with specific dimensions. The geoid, on the other hand, coincides with that surface to which the oceans would conform over the entire Earth if free to adjust to the combined effect of the Earth's mass attraction (gravitation) and the centrifugal force of the Earth's rotation. As a result of the uneven distribution of the Earth's mass, the geoidal surface is irregular and, since the ellipsoid is a regular surface, the separations between the two, referred to as geoid undulations, geoid heights, or geoid separations, will be irregular as well. The geoid is a surface along which the gravity potential is everywhere equal and to which the direction of gravity is always perpendicular (see equipotential surface).

The first flownet pictured here (modified from Craig, 1997) illustrates and quantifies the flow which occurs under the dam (flow is assumed to be invariant along the axis of the dam -- valid near the middle of the dam); from the pool behind the dam (on the right) to the tailwater downstream from the dam (on the left). There are 16 green equipotential lines (15 equal drops in hydraulic head) between the 5 m upstream head to the 1m downstream head (4 m / 15 head drops = 0.267 m head drop between each green line). The blue streamlines (equal changes in the streamfunction between the two no-flow boundaries) show the flowpath taken by water as it moves through the system; the streamlines are everywhere tangent to the flow velocity. Example flownet 2, click to view full-size.

389–390 So-called "tingle voltage filters" may be required in the electrical distribution system for a milking parlour. Connecting the neutral to the equipment case provides some protection against faults, but may produce a dangerous voltage on the case if the neutral connection is broken. Combined neutral and ground conductors are commonly used in electricity supply companies' wiring and occasionally for fixed wiring in buildings and for some specialist applications where there is little alternative, such as railways and trams. Since normal circuit currents in the neutral conductor can lead to objectionable or dangerous differences between local earth potential and the neutral, and to protect against neutral breakages, special precautions such as frequent rodding down to earth (multiple ground rod connections), use of cables where the combined neutral and earth completely surrounds the phase conductor(s), and thicker than normal equipotential bonding must be considered to ensure the system is safe.

The Flouwen and the artificial intelligence aboard the space-plane establish communications and the two species begin to exchange cultural and scientific knowledge. The crew witness the birth of a Flouwen youngling, while one crew member, Shirley Everett, takes a ride on Clear◊White◊Whistle (White Whistler) a Flouwen who understands the technologically oriented humans more than the others of the pod, and who is fascinated by their technology. Unfortunately for Shirley, the Flouwen morphs into rock form while thinking, leaving her stranded in the middle of the ocean and forcing a rescue operation to be mounted. The Flouwen realize the humans are travelling to the pole and warn the humans that they are approaching a period where the configuration of the star and planets of the system allow for a phenomenon where the ocean on the water lobe of Rocheworld can partially flow to the rocky lobe, due to the change in the gravitational equipotential.

Once a clean, smooth geopotential field U has been constructed matching the known GRS80 reference ellipsoid with an equipotential surface (we call such a field a normal potential) we can subtract it from the true (measured) potential W of the real Earth. The result is defined as T, the disturbing potential: : T = W-U The disturbing potential T is numerically a great deal smaller than U or W, and captures the detailed, complex variations of the true gravity field of the actually existing Earth from point-to-point, as distinguished from the overall global trend captured by the smooth mathematical ellipsoid of the normal potential. Due to the irregularity of the Earth's true gravity field, the equilibrium figure of sea water, or the geoid, will also be of irregular form. In some places, like west of Ireland, the geoid—mathematical mean sea level—sticks out as much as 100 m above the regular, rotationally symmetric reference ellipsoid of GRS80; in other places, like close to Ceylon, it dives under the ellipsoid by nearly the same amount.